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Creating Business Applications With REBOL

By: Nick Antonaccio
Updated: 8-24-2013
Learn to solve common business data management problems with a versatile development tool that's simple enough for "non-programmers".
See http://re-bol.com/examples.txt for a complete REBOL code reference.
Go to http://rebolforum.com to ask questions.
See also 68 YouTube video tutorials about REBOL (10 hours of video).
A tutorial about using REBOL with the Etsy API is available here.
A slideshow presentation covering the introduction of this text is available here.

Contents:

1. The Case for Non-Programmers "Learning to Program" with REBOL
1.1 Motivations and Road Blocks
1.2 Why "Off the Shelf" Software is Prevalent, but Rarely Ideal
1.3 Paper and Pencil, Spreadsheets, and Office Applications
1.4 Custom Software Solutions
1.5 The Benefits and Challenges of "Learning to Program" Custom Software
1.6 A Uniquely Practical Tool
1.7 The Goal is to Improve Overall PRODUCTIVITY and CAPABILITY
2. A Crash Course Introduction to REBOL
2.1 Installing and Running Programs
2.2 Opening REBOL Directly to the Console
2.3 Some Short Code Examples to Whet Your Appetite
2.4 Basics of REBOL Coding
2.5 Conditional Evaluations
2.6 Some More Useful Functions
3. Lists, Tables, and the "Foreach" Function
3.1 Managing Spreadsheet-Like Data
3.2 Some Simple List Algorithms (Count, Sum, Average, Max/Min)
3.3 Searching
3.4 Gathering Data, and the "Copy" Function
3.5 List Comparison Functions
3.6 Creating Lists From User Input
3.7 Three Useful Data Storage Programs: Inventory, Contacts, Schedule
3.8 Working With Tables of Data: Columns and Rows
3.9 Additional List/Block/Series Functions and Techniques
3.10 Sorting Lists and Tables of Data
3.11 CSV Files and the "Parse" Function
3.12 Two Paypal Report Programs, Analyzed
3.13 Some Perspective about Studying These Topics
4. Using GUI Windows and Widgets to Input and Display Data
4.1 Basic Layout Guidelines and Widgets
4.2 Breathing Life Into GUI Programs - Performing Actions
4.3 GUI Language Reference
4.4 A Telling Comparison
5. Quick Review and Clarification
6. SOME COMPLETE GUI APPLICATION EXAMPLES
6.1 Generic Text Field Saver
6.2 Calculator
6.3 File Editor
6.4 Web Page Editor
6.5 Inventory List Creator
6.6 Inventory Sorter and Viewer
6.7 Contacts Viewer
6.8 Minimal Retail Cash Register and Sales Report System
6.9 Email
6.10 Scheduler
6.11 Parts Database
6.12 Time Clock and Payroll Report
6.13 Blogger
6.14 FTP Group Chat
6.15 Group Reminder
6.16 A Univeral Report Generator, For Paypal and any other CSV Table Data
6.17 Reviewing and Using the Code You've Seen To Model New Applications
7. User Defined Functions and Imported Code Modules
7.1 "Do", "Does", and "Func"
7.2 Return Values
7.3 Scope
7.4 Function Documentation
7.5 Doing Imported Code
7.6 Separating Form and Function in GUIs - The Check Writer App
7.7 A Full Featured Group Note Sharing App
8. A Few Useful Data Visualization Tools
8.1 Displaying and Sorting Data Using Spreadsheet-Like GUI Grids
8.2 Creating Graphs, Plots, and Charts with "Q-Plot"
8.3 Drawing Charts Using Raw GUI Code
8.4 Creating 3D Graphs With r3D
8.5 Using the Google Chart API
8.6 Using the "Nano-Sheets" Spreadsheet App
9. Using REBOL to Create Presentations
9.1 REBOL as Presentation Software
9.2 Some Basic Layout Ideas and a Simple Code Framework for Presentations
9.3 Using Tab Panels and Menus to Present Information
9.4 Show.r - A Useful Line-By-Line Presentation System
9.5 Creating "Screen Shot" Images of GUIs
9.6 Embedding Binary Resources (images, sounds, files etc.) in Code
9.7 Playing Sounds
9.8 Launching Code in Separate Processes
9.9 Running Command Line Applications
9.10 Creating Simple Animations
9.11 A Simple Animation Framework for Presentations
9.12 Using Animated GIF Images
9.13 And That's Just the Beginning
10. Makedoc And Other Useful REBOL Productivity Tools
10.1 Makedoc.r - HTML Document Builder
10.2 An Improved Text Editor
10.3 GUI Builders and Learning Tools
11. Real World Concerns and Examples: Why "Programming" > Office Software
11.1 An Expanded Inventory Program
11.2 Receipt Printer
11.3 Advanced Time Clock and Automated Payroll Reports
12. More REBOL Language Fundamentals
12.1 Comments
12.2 Function Refinements
12.3 White Space and Indentation
12.4 Multi Line Strings, Quotes, and Concatenation
12.5 More About Variables
12.6 Data Types
12.7 Random Values
12.8 More About Reading, Writing, Loading, and Saving to and from Varied Sources
12.9 Understanding Return Values and the Order of Evaluation
12.10 More About Conditional Evaluations
12.11 More About Loops
12.12 More About Why/How Blocks are Useful
12.13 REBOL Strings
13. More Essential Topics
13.1 Built-In Help and Online Resources
13.2 Saving and Running REBOL Scripts
13.3 "Compiling" REBOL Programs - Distributing Packaged .EXE Files
13.4 Common REBOL Errors, and How to Fix Them
14. Creating Web Applications using REBOL CGI
14.1 An HTML Crash Course
14.2 A Standard CGI Template to Memorize
15. Example CGI Applications
15.1 Form Mail
15.2 A Generic Drop Down List Application
15.3 Photo Album
15.4 Simple Interactive REBOL Web Site Console
15.5 Attendance
15.6 Bulletin Board
15.7 GET vs POST Example
15.8 Group Note System
15.9 Generic Form Handler
15.10 File Uploader
15.11 File Downloader
15.12 A Complete Web Server Management Application
15.13 The RebolForum.com CGI Code
15.14 Etsy Account Manager
15.15 A Note About Working With Web Servers
15.16 WAP - Cell Phone Browser CGI Apps (deprecated)
16. Organizing Efficient Data Structures and Algorithms
16.1 A Simple Loop Example
16.2 A Real Life Example: Checkout Register and Cashier Report System
17. Additional Topics
17.1 Objects
17.2 Ports - Fine Grained Access to Files, Email, Network and More
17.3 Console and CGI Email Apps Using Ports
17.4 Network Ports - Transferring Data and Files with HTTP
17.5 Transferring Binary Files Through TCP Network Sockets
17.6 Transferring Data Through UDP Network Ports
17.7 Parse (REBOL's Answer to Regular Expressions)
17.8 Using Parse to Load Speadsheet CSV Files and Other Structured Data
17.9 Using Parse's Pattern Matching Mode to Search Data
17.10 Responding to Special Events in a GUI - "Feel"
17.11 2D Drawing, Graphics, and Animation
17.12 3D Graphics with r3D
17.13 Several 3D Scripts Using Raw REBOL Draw Dialect
17.14 Sprite Sheets
17.15 Multitasking
17.16 Using DLLs and Shared Code Files in REBOL
17.17 A Multiple Network Security Camera App Using The Window's Webcam DLL
17.18 REBOL as a Browser Plugin
17.19 Using Databases
17.20 Menus
17.21 Creating Multi Column GUI Text Lists (Data Grids) From Scratch
17.22 RebGUI
17.23 RebGUI Apps - Spreadsheet, Rolodex, Member Manager, Editor, POS system
17.24 Creating PDF files using pdf-maker.r
17.25 Bar Codes
17.26 Creating .swf Files with REBOL/Flash
17.27 Printing With REBOL
17.28 A Remote Check Printing Application
17.29 Creating Apps on Platforms That Don't Support GUI Interfaces
17.30 Encryption and Security
17.31 Rebcode
17.32 Useful REBOL Tools: XML, Zip, Database, Network, Web Server, and More
17.33 6 REBOL Flavors
17.34 Bindology, Dialects, Metaprogramming and Other Advanced Topics
18. REBOL on Android, Open Source R3 (Saphirion Builds), and RED
18.1 Open Source
18.2 Creating an Android Working Environment - Necessary Tools
18.3 R3 GUI Basics
18.4 Simple Requestors
18.5 Layout
18.6 Styles
18.7 Some More Simple Examples
18.8 Additional Essential Resources
18.9 RED
19. REAL WORLD CASE STUDIES - Learning To Think In Code
19.1 Case: Scheduling Teachers
19.2 Case: A Simple Image Gallery CGI Program
19.3 Case: Days Between Two Dates Calculator
19.4 Case: Simple Search
19.5 Case: A Simple Calculator Application
19.6 Case: A Backup Music Generator (Chord Accompaniment Player)
19.7 Case: FTP Tool
19.8 Case: The "Jeoparody" Training Program
19.9 Case: Scheduling Teachers, Part Two
19.10 Case: An Online Member Page CGI Program
19.11 Case: A CGI Event Calendar
19.12 Case: Media Player (Wave/Mp3 Jukebox)
19.13 Case: Guitar Chord Chart Printer
19.14 Case: Web Site Content Management System (CMS), Sitebuilder.cgi
19.15 Case: Downloading Directories - A Server Spidering App
19.16 Case: Vegetable Gardening
19.17 Case: An Additional Teacher Automation Project
20. Game Programming to Improve Algorithmic Thought and Graphic Skills
20.1 Case: More About Creative Algorithmic Thought: a Tetris Clone
20.2 Case: More Full Program Loops: Ski, Snake, and Invaders
20.3 Case: A GUI Playing Card Framework (Creating a Freecell Clone)
20.4 Case: Creating the REBOL "Demo"
21. Other Scripts
21.1 Thumbnail Maker
21.2 Loops and Conditions - A Simple Data Storage App
21.3 Listview Multi Column Data Grid Example
21.4 Image Effector
21.5 Little Menu Example
21.6 Shoot-Em-Up Video Game
21.7 Bingo Board
21.8 Voice Alarms
21.9 Odds and Ends
22. Learning More About REBOL - Important Documentation Links
23. Beyond REBOL
24. About The Author
24.1 My Businesses
24.2 Client List and Previous Experience
24.3 Contact Me

1. The Case for Non-Programmers "Learning to Program" with REBOL

1.1 Motivations and Road Blocks

Computer technology provides tremendous potential ability to improve productivity in all areas of business. Simple technology solutions can improve performance in accounting, inventory management, point of sale, billing, collections, scheduling, payroll, project management, marketing, sales, manufacturing, communications, and other critical processes. In today's environment, hardware, software, and network connectivity are all inexpensive commodities, and a minimal level of computing competence is expected of employees in all levels of business organization. Using available technology only increases competitive edge and improves bottom line results.

For those reasons, the core activities in many modern industries consist of using custom designed software. Additionally, programs such as Excel, Access, and Quickbooks are employed to perform daily data processing routines. Skill with these software tools is essential in various job positions, but "programming" skills are rarely considered essential for all but professional developers.

Of course, that's not surprising. Despite potential benefits, "learning to program" is a deep topic, and the path to acquiring specific software development abilities can be overwhelmingly confusing and time consuming. The productive benefits may be apparent to some people, but the learning process can be so challenging and long winded that even approaching the fundamental concepts is a tremendous hurdle. An accountant who needs to perform complex manipulations with spreadsheet data may decide that "learning to program" is worth the effort. A marketing manager who regularly uses web and email technology may also contemplate the benefits of "learning to program". An IT manager who encounters repeated software installation and use problems may likewise consider "learning to program". In those three cases, the path to "learning to program", the skill sets, and the end goals, are quite different. Each track generally involves studying incompatible tools and approaches. The accountant may learn VBA to add extended data processing features to spreadsheets. The marketer may learn just enough HTML, CSS, Javascript, PHP, MySQL, Linux and server infrastructure, etc., to customize existing open source scripts. The IT staff may learn some Python, AutoIt, or other scripting tool to create software installation packages and to automate user interaction. Learning to connect data between applications in those diverse paradigms, however, requires much deeper experience. Just supporting multiple mobile, desktop, and web platform user interfaces, for example, increases the learning curve dramatically - to the point that learning those skills is simply not practical.

The path to learning a full gamut of useful "business programming" skills traditionally involves exploring dissimilar development methodologies, conflicting approaches to design and workflow, varied IDEs, libraries, tool chain preferences, and a generally confusing mess of technologies that leaves those with even the greatest motivation, lost in apparently endless complex study. Owners, managers, others involved in strategic planning and operations - even IT staff - rarely have the time to dig deeply enough into "learning to program" to actually make it worth while. That work is left to developers.

1.2 Why "Off the Shelf" Software is Prevalent, but Rarely Ideal

In any business, solutions to critical operational road blocks are required immediately. Implementing existing third party software generally provides a quick solution to any computing task at hand, and normally yields successful short term results. For this reason, using off-the-shelf computing products is the favored approach to solving technology problems.

The typical "square peg in a round hole" computing problem discovered by managers in all industries is that off-the-shelf software packages are designed to be sold to the largest possible number of users across a given industry. Such applications are rarely a perfect fit for the exact use any business requires. Point of sale, inventory, and accounting systems developed to serve the needs of all the businesses in an industry, for example, are either too bloated and complex, too simple, or lack specific features an individual user requires for their chosen pattern of operations. Businesses are forced to adjust their operating procedures to fit the features provided by one-size-fits-all, preconceived software solutions. Project managers may go through a lengthy and expensive process of determining which available commercial packages come closest to fitting their needs. Implementation, training, and technical support costs related to testing, installing, using, and maintaining such packages typically impose significant IT expense. Workers become reliant on installed software, and a combination of incompatible third party packages leads to large scale, mission critical systems comprised of components which don't work well together. Expensive daily labor is required to repeatedly integrate data between mismatched software solutions. When business needs change enough to exceed the limitations of existing software packages - and that situation is encountered at some point in almost every business experience - data often must be migrated to entirely new software, re-training is required, the risk of potential incompatibilities and necessary costly updates increases, and productivity is severely interrupted. You've probably witnessed this condition at businesses which have publicly visible operations: problems at a retail store, bank, or service center where "the new computer system" is giving workers difficulty.

A familiar solution to avoiding upgrade problems, protecting investment in existing systems, improving functionality and interoperability, and dealing with inevitable changes to software requirements, is to build third party add-ons and extensions. For example, it's common that small businesses require special reports which aren't possible using the built in reporting capabilities of Quickbooks. Using data exported from Quickbooks, such reports are easily created with MS Access, but the process of creating the new report in Access, performing routine exports, running the third party program, importing data, etc., is time consuming and error prone. The potential to build macros and/or to make use of scripting APIs in many software packages, in order to automate such complex routines, only adds layers of complexity and commitment to fundamentally imperfect generic software solutions, and may actually encourage time consuming error prone usage patterns. As it turns out, building add-ons, macros, and other glued together solutions often requires more total time, money, and repeatedly wasted effort for everyone involved. It's not uncommon for hacked together computing systems to drain more resources than the original problem they intended to solve, especially when the solution is used by many workers in an organization.

1.3 Paper and Pencil, Spreadsheets, and Office Applications

For small projects and trivial daily routines, software solutions are likely never even considered an option. Other less perfectly engineered approaches are chosen to solve small daily problems that impact productivity negatively. Normally, such "other" solutions make use of whatever accessible tools are on hand to provide a functional solution. Very often, workers use paper and pencil to manage simple daily activities. Small bits of scheduling, payroll, inventory, sales, accounting, departmental communications, and other data can be found floating around offices regularly on pieces of paper, before being entered into "official" computing systems. Often, such routines and patterns could be dramatically improved, error proofed, standardized, and made more efficient using simple custom apps. Ideally, those simple apps could ultimately be integrated into the core business software package and workflow routine.

Beyond paper, pencil, hand held calculators, and other manual shortcuts, spreadsheets are the most used tool. This is understandable because spreadsheets provide an intuitive free-form user interface for neatly entering, selecting, copying and altering data, and formulas for performing computations on units and lists of data values. In many cases, specifically when totaling columns of numerical values, this paradigm works perfectly (because it is a spreadsheet's fundamental use case). For this purpose, spreadsheets are ubiquitous, and are in fact considered a requirement for working in job positions which routinely deal with lists of data. Accountants, inventory managers, sales people, payroll managers, scheduling managers, secretaries, etc., use them to tally numbers, enter schedule info, collate HR data, and to organize and share daily information management tasks.

Unfortunately, simply because spreadsheets are so powerful and ubiquitous, they are often overused and misused. For applications which require multiple user input, protected data fields, large data sets, special searching, sorting and reporting capabilities, parsed data operations (data mining), and many other typical workflow cases, spreadsheets can be error prone, awkward, and under powered tools. Spreadsheets also encourage users to create their own independent workflows, storing important bits of data in obscure personal files which are scattered, lost, and never effectively integrated into larger routine patterns of operation.

For several detailed analyses of how spreadsheets are overused and/or used inappropriately, with problematic results, see:

  1. Are Spreadsheets Running Your Business?
  2. Spreadsheet Addiction
  3. Databases versus spreadsheets - do you know where your data is?
  4. Excel to R

1.4 Custom Software Solutions

The ideal solution to all these types of problems is to create custom software applications, designed from the ground up to satisfy the specific data management needs of a given business. This typically leads to dramatically simplified, cleaner, multi-user capable, faster and less error prone user interfaces, and provides a much simpler path to adjusting core design and usage patterns as data management needs evolve. Custom apps provide focused solutions to specific work routines, with streamlined user interfaces that speed use, ease data input and output, and eliminate errors.

It's typically a trivial task for developers to produce software that effectively replaces spreadsheets. In many cases, creating a simple graphical user interface ("window", "form", etc.) which provides form validation and restricted access to fields of data, is all that's needed to manage daily data processing routines with greater facility, fewer mistakes, and better integration with a fully engineered system. In more complex cases, migrating information to a database system may be all that's required to enable multi-user access and to provide enhanced reporting abilities. In some cases, basic access to file system, network protocols, email, hardware, and other resources attached to a computer system are the only requirements for building useful apps which dramatically improve productivity in routine tasks. Searching for matching data patterns in files and performing conditional operations to send form emails to appropriate users, for example, is a simple utility task for a "developer", which can't be easily accomplished using mainstream office software. Simple, custom designed applications, created to manage specific tasks, and engineered to work together within a larger design, will almost always gracefully replace larger systems that have been patched together using pre-boxed solutions, spreadsheets, scripted interface and macro tools, data conversion routines, and other disparate components.

Custom software also adds to the equity value of a business, not just in terms of saved expenses and added intellectual property, but also because it clarifies and codifies the fundamental processes that make up the operating model which defines the business itself. Businesses which implement and assert repeatable models of operation are more easily expanded, scaled up, franchised, sold, etc. Simply understanding how, when, and why such custom apps can and should be built, enables an enormous competitive advantage.

1.5 The Benefits and Challenges of "Learning to Program" Custom Software

Given the challenges inherent in "learning to program", to engineer effective large scale, mission critical applications, the only apparent solution is to outline required specifications and then hire developers to create well designed software. The disadvantage of this arrangement, beyond it's initial expense, is that managers become tied to working with their chosen developer(s), and are limited by the contractor's schedule, creative/technical abilities, and understanding of the industry in which the software is used. It's not unusual for contracted developers to live apart from, and quite unaware of, the environment and conditions in which their creations are used. The realistic way in which operational stresses impact how their software is used may not always be fully communicated. Although the contractor solution can be effective, and is often the only choice available, it's critical for project managers to understand the options, benefits and drawbacks of every development choice available. A functional understanding of programming, even simple prototyping, helps to improve the development process and the outcome, even when managers (owners, workers, or other in-house personnel) write 0 lines of production code.

From quick utilities to large scale applications, and for all of the cases when a custom developed application is the most appropriate and productive solution, there is practical value in having mastered general "coding" skills. Not only is it useful to imagine and actually create utilities and applications, having a working knowledge of programming allows decision makers in businesses of all types to make informed choices about envisioning, evaluating, and commissioning software solutions to improve bottom line results. Understanding the benefits, drawbacks, extensibility limits, and infrastructure decisions required to create and implement any available technology solution is critical for effective decision making. It's of course important for developers and IT professionals to understand these topics, but when managers, owners, and users all share at least some fundamental knowledge, it becomes easier to communicate about specification details, and in fact about the very possibility of using software technology in smarter ways to improve productivity in the first place. Developers are far more likely than others to imagine simple software solutions to repeated problematic workflow patterns which reduce productivity and shrink bottom line results.

So "learning to program" may occasionally strike technically minded business people as a great idea. The problem is that "learning to program" with any real scope of useful skill is a deceptively difficult goal to achieve. There are an enormous variety of development tools available today. Picking a tool set and a learning path toward the goal of actually writing useful software in a variety of application domains can be even more time consuming and confusing than learning the required language(s). That's in fact a fundamental reason why "learning to program" is not a mainstream goal or expectation. The void between learning Excel and understanding general purpose programming has traditionally been considered too large a topic to be concisely understood, let alone applied to a variety of real world business use cases. Java and the C languages are powerful, popular, well supported, and capable of providing solutions to a full range of domain problems. Scripting languages such as Python, Ruby, and Lua, and IDE tools such as Visual Basic are powerful and easier to learn. But these languages and tool sets are still not designed for "non-programmers". The syntax of most languages is initially truly foreign, and the workflow is not immediately productive. Just the amount of time required to learn fundamental concepts needed to create a window with some text fields and buttons, and enough API understanding to do something actually useful with the entered data is well beyond the interest threshold of most professionals who entertain a fleeting interest in "learning to program". The enormous amount of effort required to "learn programming" will almost always draw too much time and energy away from more productive, income producing business efforts. That's why owners, managers, and workers typically never go beyond learning limited software tools such as Excel.

The problem is that there are just not any simple, self contained instructional packages that teach a full set of useful business programming skills at a level that attracts and maintains the interest of "non-programmers" who display initial curiosity. Potentially willing students are expected to read tens of thousands of pages about each programming paradigm, and spend years becoming intimately familiar with an enormous variety of language skills, development environments, APIs, IDEs and other coding tools, database systems, disparate work patterns, etc., before they can accomplish even a modest variety of practical programming goals safely and effectively. Learning to crunch a table of numbers and make an acceptable presentation with Excel is something that can be accomplished in a day. There are plenty of books and web sites available which get motivated users to that point, immediately. That is not the case for traditional programming languages.

1.6 A Uniquely Practical Tool

To find an ideal solution, it's essential to look beyond mainstream approaches and tools. The REBOL language and tool set is perfectly suited to business people who need to be productive with their time. REBOL was designed with that goal in mind, and it can be successfully learned and applied to that end, through a smoothly progressive learning curve, by "non-programmers" (professionals who fill a work schedule with activities other than writing code). No language is simpler to learn and use, and the path to understanding user interface creation, list and table data processing, web programming, mathematical analysis and reporting, parsing and data mining, graphic layout and presentation, and other essentially useful goals is more straight forward than with any other general purpose development tool. A strong understanding of how to create everything from quick and dirty utilities to full scale commercial applications can be achieved and put to use with even less effort than is required to perform advanced spreadsheet scripting. In REBOL, creating a program window with a button that emails the contents of a file to a group of people, is as simple as:

view layout [
    button [
            send [bob@site.com ed@site.com amy@site.com] read %file.txt
        ]
    ]
]

That's a functional, working program with a windowed user interface (i.e., one that uses buttons, fields, and other graphic controls, instead of text commands typed into a console).

The short script below downloads a Paypal account file from the web and calculates the sum of all values in the "Gross" transactions column (col #8). Writing this code takes less time than downloading the file with a browser, opening a spreadsheet program, importing the data, and summing the numbers with a formula. It also only needs to be written once, and executed any time the live data changes. Using a spreadsheet would require a complete download/import/run cycle for every change to the data source. Complex conditional and algorithmic evaluations, nearly impossible to accomplish with a spreadsheet, would require only a few lines of code added to this example:

sum: $0
foreach line at read/lines http://re-bol.com/Download.csv 2 [
    sum: sum + to-money pick (parse/all line ",") 8
]
alert join "Total Gross Sales: " sum

This program creates a graphic bar chart from a list of numbers:

do %q-plot.r
view quick-plot [
    600x400
    bars [5 3 8 2 10 3 4 9 5 7]
]

Training employees to copy, paste, run, and even edit/extend the above code samples requires no more time than teaching them to use an email or spreadsheet application, and the installation/maintenance costs are $0.00. REBOL is a free, open source, 1/2 megabyte app that can be downloaded, installed, and run on any operating system in less than a minute. That's not true of any comparably powerful office application.

But the examples above just scratch the surface. REBOL has a striking ability to simplify difficult computing tasks of all types, with straightforward, extremely high level code dialects. No other development tool is as adept at making use of practical domain specific languages ("DSLs") which lower barriers to accomplishing the full gamut of useful programming tasks. Well designed language dialects virtually eliminate the traditional obstacles inherent in understanding core topics and acquiring new skills, to such a critically low point of simplicity that even "non-programmers" are immediately able to grasp and productively use clearly defined code patterns of all types. Creating graphic plots of number lists, building full screen presentations, creating visual forms to accept text input from users, parsing and performing math computations on columns of log data from web applications, searching and sorting values of all types, performing powerful conditional evaluations based on search results and value comparisons, and many much more complicated operations, all take just a few minutes to learn how to accomplish, using simple DSLs and native REBOL language features.

In addition to DSLs, REBOL uses a single universal code structure to store, manipulate, and transfer all data. Lists, tables, and even sizable databases of mixed text, code, and binary data are all created using one consistent "block" syntax. Like everything else in REBOL, block format is brutally simple, but it enables many powerful features for searching, sorting, comparing, dissecting, evaluating, storing, retrieving, transferring and otherwise manipulating information of all types. In many simple use cases, the need to even choose a database system, learn SQL, explore third parties libraries, and all the overhead related to managing such typical programming requirements, is simply bypassed. And because REBOL is one of the most portable languages in existence, these benefits are available and compatible on every operating system for which REBOL has been compiled (more than 40, and counting). The initial REBOL learning experience and all tooling is immediately and directly applicable to building desktop, server, web and mobile software. In REBOL, strings and other series data constructs all make use of the exact same functions as blocks, so the learning curve for performing every type of list and table data processing is greatly reduced. Common network protocols and data values are also natively accessed in REBOL, using the simplest possible syntax. Users can read and write data directly to/from databases, web servers, email accounts, and more, add/subtract time, date, tuple, and other values automatically, manipulate CSV, XML, HTML and other formats natively, display and apply effects to images and graphics, play sounds, etc., all without any complex formatting or any external library code. REBOL has a built in, powerful "parse" dialect which elegantly replaces the need for regular expressions when extracting data from both structured and unstructured sources.

And since REBOL is a tiny (about 1/2 a meg) multi-platform interpreter, it can be downloaded and used immediately, without installation, on all platforms as a lightweight file manager, text editor, calculator, database manager, email client, ftp client, news reader, image viewer/editor, OS shell, and more. You can employ it as a simple utility program with a familiar interface to common computing activities, on just about any computer, even if you're unfamiliar with the operating system. All REBOL applications, and the entire development system itself, is instantly transportable. You can even send complex REBOL scripts along with all the REBOL interpreters for Windows, Mac, and Linux as a tiny email attachment smaller that a single photograph. Complex scripts will operate and appear exactly the same visually to every user, using every type of computer, without any other required software installation dependencies, operating system or version updates, data conversion or reformatting work, etc. REBOL's size, portability, and free cost remove all limitations to transferring, computing, and presenting data in any environment, using any standard equipment.

The list of such practical features goes on and on, but REBOL is not built from shortsighted gimmicks. It is a deep and powerful tool that encompasses solutions to a diverse set of problems, using a simple unified approach. Dialects enable intuitively human access - via simple language constructs - to powerful layers of technology. Because so many deep, varied layers of practical capability are all built into REBOL, and because all those elements interact natively, the learning curve required to get real work done is much easier, and more power over a broader scope is enabled, than in other development environments.

1.7 The Goal is to Improve Overall PRODUCTIVITY and CAPABILITY

Empowering a versatile approach to solving common data management problems found across a variety of domains of business operations, using a single tool designed to be simple enough for "average computer users" to learn, is what this tutorial aims to accomplish. The end result of studying this text is to increase productivity and capability in ways that are otherwise impossible to achieve. Although it might be possible to achieve this goal with a smart curriculum based on other mainstream development tools, in this author's experience, REBOL is the best fit for the intended audience ("non-programmers").

In order for business programming to be productive, the time invested in studying and writing code must be less than the time and money saved by implemented software solutions. This text is intended to cover the entire scope of learning, with no additional required resources. It begins with an essential absolute beginner tutorial, and progresses through numerous case studies demonstrating how real world applications were developed to solve problems in a variety of domains. By the end, the reader will have a solid understanding of all the code required to build powerful multi-platform desktop applications, server programs, web scripts and mobile apps that solve the overwhelming majority of data management problems encountered in common business scenarios (not just concepts, but actual working code). More than 100 complete working application examples will be explored in depth, and absolutely no previous programming experience is required to get started. Those applications are free to use, modify, and combine for your own purposes. Once complete, the benefits and drawbacks of learning other development tools will be much easier to understand, but in many cases, those traditional tools may never be needed by the "non-programmers" who are attracted to this text.

At very least, studying this text will enable the ability to use a tool that's far more versatile than spreadsheets and other familiar office software. More than likely, in any business that involves managing the activities of even a few employees, the skill of computer programming will find repeated practical application. Even if that skill is not regularly employed, the insight that comes from understanding how to imagine new software tools and design program specifications and algorithms to solve problems, is practical for anyone who intends to engineer improved business processes.

The combination of an appropriately focused curriculum and a uniquely approachable tool set, takes the task of "learning to program" for business from the realm of virtually impossible to quite approachable, for anyone who wants to put in the time and intellectual effort. Learning to envision and then actually create usable, safe, practical software applications is not an easy endeavor, but it is doable and can be tremendously rewarding ... and it provides true long term potential to increase productivity and improve bottom line profits in any business.

2. A Crash Course Introduction to REBOL

2.1 Installing and Running Programs

To get started, download and install REBOL/View from http://www.rebol.com/download-view.html (it takes just a few seconds).

Once it's installed, run REBOL (Start -> Programs -> REBOL -> REBOL View), then click the "Console" Icon.

Type "editor none" at the prompt - that will run REBOL's built in text editor.

At this point, you are ready to start typing in REBOL programs. Copy/paste each example from this tutorial into the REBOL editor to see what the code does. Try it right now. Paste the following code into the REBOL editor, then press [F5] on your keyboard to save and run the program. You can save the file using the default "temp.txt" file name, as prompted, or rename it if you'd like. If you see the REBOL security requestor, select "Allow all":

REBOL []
alert "Hello World!"

If you save your program with a ".r" extension in the file name (i.e., "myprogram.r"), then you can also click your saved program's file icon, and it will run just like any normal executable (.exe) file. Try saving the program above on your desktop as "hello.r", then run it by clicking the hello.r icon on your desktop with your mouse.

2.2 Opening REBOL Directly to the Console

Before typing in or pasting any more code, adjust the following option in the REBOL interpreter: click the "User" menu in the graphic Viewtop that opens by default with REBOL, and uncheck "Open Desktop On Startup". That'll save you the trouble of clicking the "Console" button every time you start REBOL.

Setting your email account information and other user settings, is also recommended at this point.

2.3 Some Short Code Examples to Whet Your Appetite

Here are some REBOL program examples which demonstrate the simple and concise nature of REBOL code. Paste each program into the REBOL editor and press [F5] to see it run. Read briefly through each line of the programs to familiarize yourself with what REBOL code looks like. You'll understand exactly how everything works, very shortly.

Here's a short and useful example that saves text field data to a text file. It can be used as the basis for entering and saving categorical units of data of almost every type, for receipts, notes, etc.

REBOL [title: "Text Field Saver"]
view layout [
    f1: field
    f2: field
    f3: field
    btn "Save Fields" [
        write/append %fields.csv rejoin [
            mold f1/text ", " mold f2/text ", " mold f3/text newline
        ]
        alert "Added to File"
    ]
]

Here's an example of a text editor program that allows you to read, edit, and save any text file:

REBOL [title: "Text Editor"]
view layout [
    h1 "Text Editor:"
    f: field 600 "filename.txt"
    a: area 600x350 
    across 
    btn "Load" [
        f/text: request-file
        show f
        filename: to-file f/text
        a/text: read filename 
        show a
    ]
    btn "Save" [
        filename: to-file request-file/save/file f/text
        write filename a/text
        alert "Saved"
    ]
]

Here's a variation of the program above, repurposed as a web page editor (this program can actually be used to edit real, live web pages on the Internet):

REBOL [title: "Web Page Editor"]
view layout [
    h1 "Web Page Editor:"
    f: field 600 "ftp://user:pass@site.com/public_html/page.html"
    a: area 600x350 
    across 
    btn "Load" [
        a/text: read to-url f/text 
        show a
    ]
    btn "Save" [
        write (to-url f/text) a/text
        alert "Saved"
    ]
]

Here's a basic calculator app:

REBOL [title: "Calculator"]
view layout [
    origin 0  space 0x0  across
    style btn btn 50x50 [append f/text face/text  show f]
    f: field 200x40 font-size 20 return
    btn "1"  btn "2"  btn "3"  btn " + "  return
    btn "4"  btn "5"  btn "6"  btn " - "  return
    btn "7"  btn "8"  btn "9"  btn " * "  return
    btn "0"  btn "."  btn " / "   btn "=" [
        attempt [f/text: form do f/text  show f]
    ]
]

Here's a variation of the Paypal example from this tutorial's introduction. It downloads a Paypal account file from the web and reports the sum of all gross account transactions, displays all purchases made from the name "Saoud Gorn", and computes the total of all transactions from "Ourliptef.com" which occured between midnight and noon hours. Try running it on a computer that's connected to the Internet:

REBOL [title: "Paypal Reports"]
sum1: sum2: $0
foreach line at read/lines http://re-bol.com/Download.csv 2 [
    sum1: sum1 + to-money pick row: parse/all line "," 8
    if find row/4 "Saoud" [print rejoin [row/1 ", Saoud Gorn: " row/8]]
    if find row/4 "Ourliptef.com" [
        if (0:00am <= time: to-time row/2) and (time <= 12:00pm) [
            sum2: sum2 + to-money row/8
        ]
    ]
]
alert join "GROSS ACCOUNT TRANSACTIONS: " sum1
alert join "2012 Ourliptef.com Morning Total: " sum2

This example extends the reports above with graphs of the collected data (Internet connection required for this example too):

REBOL [title: "Paypal Report Charts"]
transactions: copy []
saoud: copy []
dates: copy []
foreach line at read/lines http://re-bol.com/Download.csv 2 [
    row: parse/all line ","
    append transactions to-integer row/8
    if find row/4 "Saoud" [
        append saoud to-integer row/8
        append dates replace row/1 "/2012" ""
    ]
]
if not exists? %q-plot.r [write %q-plot.r read http://re-bol.com/q-plot.r]
do %q-plot.r
view center-face quick-plot [
    594x400
    bars [(data: copy transactions)]
    label "All Paypal Transactions"
]
view center-face quick-plot [
    495x530
    pen blue
    pie [(data: copy saoud)] labels [(data: copy dates)] explode [1 2 3]
    title "Saoud" style vh2     
]

Here's a slighty more mature version of the first example in this section. This program creates an inventory list using a simple GUI form (a window with some text fields and buttons). The file created could be used, for example, to determine re-order requirements, to calculate inventory and sales tax due, or sent to an accountant to be imported and used in a spreadsheet, etc.:

REBOL [title: "Inventory"]
view layout [
    text "SKU:"
    f1: field
    text "Cost:"
    f2: field "1.00"
    text "Quantity:"
    f3: field
    across
    btn "Save" [
        write/append %inventory.txt rejoin [
            mold f1/text " " mold f2/text " " mold f3/text newline
        ]
        alert "Saved"
    ]
    btn "View Data" [editor %inventory.txt]
]

This program allows users to view the inventory data created by the program above, sorted by any chosen column:

REBOL [title: "Sort Inventory"]
inventory: load %inventory.txt
blocked: copy []
foreach [sku cost qty] inventory [
    append/only blocked reduce [
        sku 
        to-money cost
        to-integer qty
    ]
]
field-name: request-list "Choose Field To Sort By:" [
    "sku" "cost" "qty"
]
field: select ["sku" 1 "cost" 2 "qty" 3] field-name
order: request-list "Ascending or Descending:" ["ascending" "descending"]
either order = "ascending" [
    sort/compare blocked func [a b] [(at a field) < (at b field)]
][
    sort/compare blocked func [a b] [(at a field) > (at b field)]
]
foreach item blocked [
    print rejoin [
        "SKU:  " item/1 "  COST: " item/2 "  QTY: " item/3 newline
    ]
]
halt

Here's a little contact database app that displays user information in a tabular display:

REBOL [title: "Contacts"]
users: [
    "John Smith" "123 Tomline Lane Forest Hills, NJ" "555-1234"
    "Paul Thompson" "234 Georgetown Pl. Peanut Grove, AL" "555-2345"
    "Jim Persee" "345 Pickles Pike Orange Grove, FL" "555-3456"
    "George Jones" "456 Topforge Court Mountain Creek, CO" ""
    "Tim Paulson" "" "555-5678"
]
gui: [
    backdrop white
    across
    style header text black 200
    header "Name:" header "Address:" header "Phone:" return
]
foreach [name address phone] users [
    append gui compose [
        field (name) field (address) field (phone) return
    ]
]
view layout gui

Here's a simple email app:

REBOL [title: "Email"]
view layout[
    h1 "Send:"
    btn "Server settings" [
        system/schemes/default/host: request-text/title "SMTP Server:"
        system/schemes/pop/host:     request-text/title "POP Server:"
        system/schemes/default/user: request-text/title "SMTP User Name:"
        system/schemes/default/pass: request-text/title "SMTP Password:"
        system/user/email: to-email request-text/title "Your Email Addr:"
    ]
    a: field "user@website.com"
    s: field "Subject" 
    b: area
    btn "Send"[
        send/subject to-email a/text b/text s/text
        alert "Sent"
    ]
    h1 "Read:" 
    f: field "pop://user:pass@site.com"
    btn "Read" [editor read to-url f/text]
]

Here's a scheduling app that allows users to create events on any day. The user can then click days on the calendar to see the scheduled events:

REBOL [title: "Schedule"]
view center-face gui: layout [
    btn "Date" [date/text: form request-date  show date]
    date: field
    text "Event Title:"
    event: field
    text "Time:"
    time: field
    text "Notes:"
    notes: field
    btn "Add Appointment" [
        write/append %appts.txt rejoin [
            mold date/text newline
            mold event/text newline
            mold time/text newline
            mold notes/text newline 
        ]
        date/text: "" event/text: "" time/text: "" notes/text: ""
        show gui
        alert "Added"
    ]
    a: area
    btn "View Schedule" [
        today: form request-date
        foreach [date event time notes] load %appts.txt [
            if date = today [
                a/text: copy ""
                append a/text form rejoin [
                    date newline
                    event newline
                    time newline
                    notes newline newline
                ]
                show a
            ]
        ]
    ]
]

Here's a small but fully functional cash register application:

REBOL [title: "Minimal Cash Register"]
view gui: layout [
    style fld field 80
    across
    text "Cashier:"   cashier: fld 
    text "Item:"      item: fld 
    text "Price:"     price: fld [
        if error? try [to-money price/text] [alert "Price error" return]
        append a/text reduce [mold item/text "    " price/text newline]
        item/text: copy "" price/text: copy ""
        sum: 0
        foreach [item price] load a/text [sum: sum + to-money price]
        subtotal/text: form sum
        tax/text: form sum * .06
        total/text: form sum * 1.06 
        focus item
        show gui
    ]
    return
    a: area 600x300
    return
    text "Subtotal:"   subtotal: fld 
    text "Tax:"        tax: fld 
    text "Total:"      total: fld
    btn "Save" [
        items: replace/all (mold load a/text) newline " "
        write/append %sales.txt rejoin [
            items newline cashier/text newline now/date newline
        ]
        clear-fields gui
        a/text: copy ""             
        show gui             
    ]
]

This program computes a sum all sales made on the current day:

REBOL [title: "Daily Total"]
sales: read/lines %sales.txt
sum: $0
foreach [items cashier date] sales [
    if now/date = to-date date [
        foreach [item price] load items [
            sum: sum + to-money price
        ]
    ]
]
alert rejoin ["Total sales today: " sum]

Here's a full screen slide show presentation example:

REBOL [title: "Simple Presentation"]
slides: [
    [
        at 0x0 box system/view/screen-face/size white [unview]
        at 20x20 h1 blue "Slide 1"
        box black 2000x2
        text "This slide takes up the full screen."
        text "Adding images is easy:"
        image logo.gif
        image stop.gif
        image info.gif
        image exclamation.gif
        text "Click anywhere on the screen for next slide..."
        box black 2000x2
    ]
    [
        at 0x0 box system/view/screen-face/size effect [
            gradient 1x1 tan brown
        ] [unview]
        at 20x20 h1 blue "Slide 2"
        box black 2000x2
        text "Gradients and color effects are easy in REBOL:"
        box effect [gradient 123.23.56 254.0.12]
        box effect [gradient blue gold/2]
        text "Click anywhere on the screen to close..."
        box black 2000x2
    ]
]
foreach slide slides [
    view/options center-face layout slide 'no-title
]

Here's a parts database application:

REBOL [title: "Parts"]
write/append %data.txt ""
database: load %data.txt
view center-face gui: layout [
    text "Parts in Stock:"
    name-list: text-list blue 400x100 data sort (extract database 4) [
        if value = none [return]
        marker: index? find database value
        n/text: pick database marker
        a/text: pick database (marker + 1)
        p/text: pick database (marker + 2)
        o/text: pick database (marker + 3)
        show gui
    ]
    text "Part Name:"       n: field 400
    text "Manufacturer:"    a: field 400
    text "SKU:"      p: field 400
    text "Notes:"      o: area  400x100
    across
    btn "Save" [
        if n/text = "" [alert "You must enter a Part name." return]
        if find (extract database 4) n/text [
            either true = request "Overwrite existing record?" [
               remove/part (find database n/text) 4
            ] [
               return
            ]
        ]
        save %data.txt repend database [n/text a/text p/text o/text]
        name-list/data: sort (extract copy database 4)
        show name-list
    ]
    btn "Delete" [
        if true = request rejoin ["Delete " n/text "?"] [
            remove/part (find database n/text) 4
            save %data.txt database
            do-face clear-button 1
            name-list/data: sort (extract copy database 4)
            show name-list
        ]
    ]
    clear-button: btn "New" [
        n/text: copy  ""
        a/text: copy  ""
        p/text: copy  ""
        o/text: copy  ""
        show gui
    ]
]

Here's a spreadsheet application, originally written in REBOL by Carl Sassenrath, which can inherently use the entire REBOL language and all it's features to process cell data (math, graphics, Internet, file and network protocols, parse, native dialogs, GUI, and all other general purpose capabilities of the language are available to functions in this tiny 68 line program):

REBOL [Title: "Rebocalc" Authors: ["Carl Sassenrath" "Nick Antonaccio"]]
csize: 100x20  max-x: 8  max-y: 16
pane: []
xy: csize / 2 + 1 * 1x0
yx: csize + 1 * 0x1
layout [
    cell: field csize edge none [enter face compute face/para/scroll: 0x0]
    label: text csize white black bold center
]
char: #"A"
repeat x max-x [
    append pane make label [offset: xy text: char]
    set in last pane 'offset xy
    xy: csize + 1 * 1x0 + xy
    char: char + 1
]
repeat y max-y [
    append pane make label [offset: yx text: y size: csize * 1x2 / 2]
    yx: csize + 1 * 0x1 + yx
]
xy: csize * 1x2 / 2 + 1
cells: tail pane
repeat y max-y [
    char: #"A"
    repeat x max-x [
        v: to-word join char y
        set v none
        char: char + 1
        append pane make cell [offset: xy text: none var: v formula: none]
        xy: csize + 1 * 1x0 + xy
    ]
    xy: csize * 1x2 / 2 + 1 + (xy * 0x1)
]
enter: func [face /local data] [
    if empty? face/text [exit]
    set face/var face/text
    data: either face/text/1 = #"=" [next face/text][face/text]
    if error? try [data: load data] [exit]
    if find [
        integer! decimal! money! time! date! tuple! pair!
    ] type?/word :data [set face/var data exit]
    if face/text/1 = #"=" [face/formula: :data]
]
compute: has [blk] [
    unfocus
    foreach cell cells [
        if cell/formula [
            either cell/text = "formula" [
                cell/text: join "=" form cell/formula
                show cell return
            ][
                if error? cell/text: try [do cell/formula] [
                    cell/text: "ERROR!"
                ]
            ]
            set cell/var cell/text
            show cell
        ]
    ]
]
lo: layout [
    bx: box second span? pane
    text "Example: type '7' into A1, '19' into B1, '=a1 + b1' into C1" 
    text "Type 'formula' into any cell to edit an existing formula (C1)."
]
bx/pane: pane
view center-face lo

The process of learning a programming language is similar to learning any spoken language (English, French, Spanish, etc.). If you move a person from the United States to Spain, you can be fairly certain that within a year, they will be able to speak Spanish adequately, even if they aren't provided any appropriate structured Spanish training or guidance. Guidance certainly helps clarify the process, but a key essential component is immersion. Immersion in code works the same way. It may be painful and confusing at first to see or comprehend a totally foreign language and environment, but diving right into code is required if you want to become proficient at "speaking" REBOL. Run each example in this section, and along the way, try changing some text headers, button labels, text field sizes, and other obvious properties to see how the programs change. Getting used to using the REBOL interpreter, becoming aware that code examples in this text are malleable, and opening your mind to the prospect and activity of actually typing REBOL code, is an important first step.

2.4 Basics of REBOL Coding

Computer programming is about processing data - that's all computers do internally (although the results of that data processing can appear, and actually end up being, magically more human). Everything you learn about in this text, therefore, will necessarily have to do with inputting, manipulating, and outputting processed data.

Every REBOL program must begin with the following header:

REBOL []

Function words perform actions upon data values. The following function examples display some data values (text, in this case) and request useful data values from users (any text after a semicolon in these examples is a human readable "comment", and is ignored completely by the REBOL interpreter):

REBOL []
alert "Hello world"      ; "ALERT" is the function word here.
editor "Hello world"     ; "Hello world" is the text data parameter.
print "Hello world"      ; 
wait 2                   ; "Wait" is the function here, "2" is the data.
request-date             ; Requestor functions get some data from a user.
request-pass
request-text/title "What is your Name?"
request-file
request-list "Choose a color:" ["Red" "Green" "Blue"]
request ["Size:" "Small" "Medium" "Large"]
request-color

Be sure to paste EVERY code example into the REBOL editor, and watch each line run.

In REBOL, the output of one function (the "return value") can be used as the input ("argument" or "parameter") of another function:

; Here, the "editor" function edits whatever date is input by the user:

editor request-date

; Here, the "alert" function displays whatever text is input by the user:

alert request-text

In REBOL you can assign data to a label word (also called a "variable"), using the colon symbol. Once data is assigned to a word label, you can use that word anywhere to refer to the assigned value:

REBOL []
balance: $53940.23 - $234
print balance
name: request-text/title "Name:"
print name
date: request-date
print date
alert "Click [OK] to continue"

You can join together, or concatenate, data values using the "rejoin" function. Try adding this line to the end of the program above:

alert rejoin [name ", your balance on " date " is " balance]

There are a variety of useful values built into REBOL:

REBOL []
alert rejoin ["Right now the date and time is: " now]
alert rejoin ["The date is: " now/date]
alert rejoin ["The time is: " now/time]
alert rejoin ["The value of PI is " pi]
alert rejoin ["The months are " system/locale/months]
alert rejoin ["The days are " system/locale/days]

REBOL can perform useful calculations on many types of values:

REBOL []
alert rejoin ["5 + 7 = " 5 + 7]
alert rejoin ["Five days ago was " now/date - 5]
alert rejoin ["Five minutes ago was " now/time - 00:05]
alert rejoin ["Added coordinates: " 23x54 + 19x31]
alert rejoin ["Multiplied coordinates: " 22x66 * 2]
alert rejoin ["A multiplied coordinate matrix: " 22x66 * 2x3]
alert rejoin ["Added tuple values: " 192.168.1.1 + 0.0.0.37]
alert rejoin ["The RGB color value of purple - brown is: " purple - brown]

Remember, programming is fundamentally about managing data, so REBOL's ability to appropriately handle operations and computations with common data types leads to greater simplicity and productivity for programmers.

2.5 Conditional Evaluations

Conditional evaluations can be performed using the syntax: "if (this is true) [do this]":

REBOL []
if (now/time > 6:00am) [alert "It's time to get up!"]

Notice the natural handling of the time value in the example above. No special formatting or parsing is required to use that value. REBOL natively "understands" how to perform appropriate computations with time and other common data types.

Use the "either" evaluation to do one thing if a condition is true, and another if the condition is false:

REBOL []
user: "sa98df"
pass: "008uqwefbvuweq"
userpass: request-pass
either (userpass = reduce [user pass]) [
    alert rejoin ["Welcome back " user "!"]
][ 
    alert "Incorrect username/password combination"
]

In the code above:

  1. The word label (variable) "user" is assigned to a text value.
  2. The variable "pass" is assigned to some text.
  3. A username/password combination is requested from the user, and the result of that function is labeled "userpass".
  4. An "either" conditional evaluation is performed on the returned "userpass" value. If the userpass value equals the set "user" and "pass" variables, the user is alerted with a welcome message. Otherwise, the user is alert with an error message.

2.6 Some More Useful Functions

Try pasting every individual line below into the REBOL interpreter console to see how each function can be used to perform useful actions:

REBOL []
print read http://rebol.com  ; "read" retrieves the data from many sources
editor http://rebol.com   ; the built in editor can also read many sources
print read %./          ; the % symbol is used for local files and folders
editor %./
write %temp.txt "test"   ; write takes TWO parameters (file name and data)
editor %temp.txt
editor request-file/only       ; "only" refinement limits choice to 1 file
write clipboard:// (read http://rebol.com)  ; 2nd parameter in parentheses
editor clipboard://
print read dns://msn.com   ; REBOL can read many built in protocols
print read nntp://news.grc.com
write/binary %/c/bay.jpg (read/binary http://rebol.com/view/bay.jpg)
write/binary %tada.wav (read/binary %/c/windows/media/tada.wav)
write/binary %temp.dat (compress read http://rebol.com)    ; COMPRESS DATA
print decompress read/binary %temp.dat                   ; DECOMPRESS DATA
print read ftp://user:pass@website.com/name.txt       ; user/pass required
write ftp://user:pass@website.com/name.txt "text"     ; user/pass required
editor ftp://user:pass@website.com/name.txt  ; can save changes to server!
editor pop://user:pass@website.com       ; read all emails in this account
send user@website.com "Hello"                                 ; send email
send user@website.com (read %file.txt)     ; email the text from this file
send/attach user@website.com "My photos" [%pic1.jpg %pic2.jpg pic3.jpg]
name: ask "Enter your name"  print name  ; request a user value in console

call/show "notepad.exe c:\config.sys"            ; run an OS shell command
browse http://re-bol.com       ; open system default web browser to a page
view layout [image %pic1.jpg]                              ; view an image
view layout [image request-file/only]         ; view a user selected image
insert s: open sound:// load request-file/only wait s close s ; play sound
insert s: open sound:// load %/c/windows/media/tada.wav wait s close s

rename %temp.txt %temp2.txt                             ; change file name
write %temp.txt read %temp2.txt                                ; copy file
write/append %temp2.txt ""     ; create file (or if it exists, do nothing)
delete %temp2.txt
change-dir %../
what-dir 
list-dir
make-dir %./temp
print read %./

attempt [print 0 / 0]                         ; test for and handle errors
if error? try [print 0 / 0] [alert "*** ERROR:  divide by zero"]

parse "asdf#qwer#zxcv" "#"                ; split strings at character set
trim "  asdf89w   we   "     ; remove white space at the beginning and end
replace/all "xaxbxcxd" "x" "q"   ; replace all occurrences of "x" with "q"
checksum read %file.txt            ; compute a checksum to ensure validity
print dehex "a%20space"                  ; convert from URL encoded string
print to-url "a space"                     ; convert to URL encoded string
print detab "tab    separated"                    ; convert tabs to spaces
print enbase/base "a string" 64  ; convert string or bin to base 64, 16, 2
print encloak "my data" "my pass"  ; encrypt and decrpyt data (AES, blow-
print decloak "iz" "my pass"  ; fish and other formats also supported
read-cgi            ; neatly parse all data submitted from a web page form
for i 1 99 3 [print i]                 ; count from 1 to 99, by steps of 3

halt           ; "HALT" stops the REBOL console from closing,
               ; so you can see the printed results.

In order to see each of the lines above execute, paste them directly into the REBOL console, instead of into the editor. When running code directly in the console, it's not necessary to include the REBOL[] header, or the "halt" function:

Really take a look at how much computing ability is enabled by each of the functions above. That short collection of one line code snippets demonstrates how to do many of the most commonly useful tasks performed by a computer:

  1. Reading data from and writing data to files on a hard drive, thumb drive, etc.
  2. Reading/writing data from/to web servers and other network sources, the system clipboard, user input, etc.
  3. Reading emails, sending emails, sending attached files by email.
  4. Displaying images.
  5. Playing sounds.
  6. Navigating and manipulating folders and files on the computer.
  7. Compressing, decompressing, encrypting, and decrypting data.
  8. Running third party programs on the computer.
  9. Reading, parsing, and converting back and forth between common data types and values.

And those lines are just a cursory introduction to a handful of built in REBOL functions. There are hundreds more. At this point in the tutorial, simply read the examples and paste them into the REBOL interpreter console to introduce yourself to the syntax, and to witness their resulting action. You will see these functions, and others, used repeatedly throughout this tutorial and in real working code, for as long as you study and use REBOL. Eventually, you will get to know their syntax and refinements by heart, but you can always refer to reference documentation while you're learning. If you're serious about learning to program, you should take some time now to try changing the parameters of each function to do some useful work (try reading the contents of different file names, send some emails to yourself, compress and decompress some data and view the results with the editor function, etc.)

You can get a list of all function words by typing the "what" function into the REBOL console:

what                             ; press the [ESC] key to stop the listing

You can see the syntax, parameters, and refinements of any function using the "help" function:

help print
help prin
help read
help write

You can learn more about all the useful functions built in to REBOL by running the following program. Try it now:

write %wordbrowser.r read http://re-bol.com/wordbrowser.r
do %wordbrowser.r

By learning to combine simple functions with a bit of conditional evaluation (if/then) thinking, along with some list processing techniques, you can accomplish truly useful programming goals that go far beyond the capabilities of even complex office suite programs (much more about 'list processing' will be covered shortly).

The important thing to understand at this point is that functions exist in REBOL, to perform actions on all sorts of useful data. Learning to recognize functions and the data parameters which follow them, when you see them in code, is an important first step in learning to read and write REBOL. Eventually memorizing the syntax and appropriate use patterns of all built in functions is a necessary goal if you want to write code fluently.

The benefit of pasting (or even better typing) every single example into the REBOL editor and/or console, cannot be overstated. Concepts will become more understandable, and important code details will be explicitly clarified as this text progresses. For now, working by rote is the best way to continue learning. Read and execute each example, and pay attention to which words are functions and which words are data arguments.

3. Lists, Tables, and the "Foreach" Function

3.1 Managing Spreadsheet-Like Data

3.1.1 Warning

NOTE: This section of the tutorial is the longest and most difficult to grasp at first read. Read through it once to introduce yourself to all the topics, and skim the code structures. Be prepared for it - the code is going to get hairy. Just press on, absorb what you can, and continue to read through the entire section. You'll refer back to it later in much greater detail, once you've seen how all the concepts, functions, and code patterns fit together to create useful programs.

3.1.2 Blocks

Most useful business programs process lists of data. Tables of data are actually dealt with programatically as consecutive lists of items. A list or "block" of data is created in REBOL by surrounding values with square brackets:

REBOL []
names: ["Bob" "Tom" "Bill"]

To perform an operation/computation with/to each data item in the block, use the foreach function. Foreach syntax can be read like this: "foreach (labeled item) in (this labeled block) [perform this operation with/to each labeled item]:

REBOL []
names: ["Bob" "Tom" "Bill"] ; create a block of text items labeled "names"
foreach name names [print name]       ; print each name value in the block
halt

This example prints each value stored in the built-in "system/locale/months" block:

REBOL []
months: system/locale/months     ; set the variable "months" to the values
foreach month months [print month]                ; print each month value
halt

Note that in the example above, the variable words "months" and "month" could be changed to any other desired, arbitrarily determined, label:

REBOL []
foo: system/locale/months
foreach bar foo [print bar]                ; variable labels are arbitrary
halt

Labeling the system/locale/months block is also not required. Without the label, the code is shorter, but perhaps just a bit harder to read:

REBOL []
foreach month system/locale/months [print month]
halt

Learning to read and think in terms of "foreach item in list [do this to each item]" is one of the most important fundamental concepts to grasp in programming. You'll see numerous repeated examples in this text. Be aware every time you see the word "foreach".

You can obtain lists of data from a variety of different sources. Notice that the "load" function is typically used to read lists of data. This example prints the files in the current folder on the hard drive:

REBOL []
folder: load %. 
foreach file folder [print file]
halt

This example loads the list from a file stored on a web site:

REBOL []
names: load http://re-bol.com/names.txt 
foreach name names [print name]     
halt

NOTE: you can write the data required for the above example to your own web server, using the following line of code. Note that the "save" function is typically used to write lists of data:

REBOL []
save ftp://user:pass@site.com/folder/names.txt ["Bob" "Tom" "Bill"]

3.2 Some Simple List Algorithms (Count, Sum, Average, Max/Min)

3.2.1 Counting Items

The "length?" function counts the number of items in a list:

REBOL []
receipts: [$5.23 $95.98 $7.46 $34]        ; a list labeled "receipts"
alert rejoin ["There are " length? receipts " receipts in the list."]

You can assign counts to variable labels and use the values later:

REBOL []
month-count: length? system/locale/months 
day-count: length? system/locale/days
alert rejoin ["There are " month-count " months and " day-count " days."]

Another way to count items in a list is to create a counter variable, initially set to 0. Use a foreach loop to go through each item in the list, and increment (add 1) to the count variable:

REBOL []
count: 0
receipts: [$5.23 $95.98 $7.46 $34]
foreach receipt receipts [count: count + 1]   ; increment count by 1
alert rejoin ["There are " count " receipts in the list."]

Here's an alternate syntax for incrementing counter variables:

REBOL []
count: 0
receipts: [$5.23 $95.98 $7.46 $34] 
foreach receipt receipts [++ count]           ; increment count by 1
alert rejoin ["There are " count " receipts in the list."]

This example counts the number of months in a year and the number of days in a week, using counter variables:

REBOL []
month-count: 0
day-count: 0
foreach month system/locale/months [++ month-count] 
foreach day system/locale/days [++ day-count]
alert rejoin ["There are " month-count " months and " day-count " days."]

Counter variables are particularly useful when you only want to count certain items in a list. The following example counts only items that are number values:

REBOL []
count: 0
list: ["screws" 14 "nuts" 38 "bolts" 23]
foreach item list [
    ; Increment only if item type is integer:
    if (type? item) = integer! [++ count]
]
alert rejoin ["The count of all number values in the list is: " count]

3.2.2 Sums

To calculate the sum of numbers in a list, start by assigning a sum variable to 0. Then use a foreach loop to increment the sum by each individual number value. This example starts by assigning the label "balance" to a value of 0. Then the label "receipts" is assigned to a list of money values. Then, each value in the receipts list is added to the balance, and that tallied balance is displayed:

REBOL []
sum: 0                                ; a sum variable, initially set to 0
receipts: [$5.23 $95.98 $7.46 $34]            ; a list, labeled "receipts"
foreach item receipts [sum: sum + item]                      ; add them up
alert rejoin ["The sum of all receipts is: " sum]

You could total only the items in a list which contain number values, for example, like this:

REBOL []
sum: 0
list: ["screws" 14 "nuts" 38 "bolts" 23]
foreach item list [
    if (type? item) = integer! [            ; only if item type is integer
        sum: sum + item                     ; add item to total
    ]
]
alert rejoin ["The total of all number values in the list is: " sum]

3.2.3 Averages

Computing the average value of items in a list is simply a matter of dividing the sum by the count:

REBOL []
sum: 0
receipts: [$5.23 $95.98 $7.46 $34]
foreach item receipts [sum: sum + item]
average: sum / (length? receipts)
alert rejoin ["The average balance of all receipts is: " average]

3.2.4 Maximums and Minimums

REBOL has built in "maximum-of" and "minimum-of" functions:

REBOL []
receipts: [$5.23 $95.98 $7.46 $34]
print first maximum-of receipts
print first minimum-of receipts
halt

You can perform more complicated max/min comparisons by checking each value with a conditional evaluation. This example looks for the highest receipt value under $50:

REBOL []
highest: $0
receipts: [$5.23 $95.98 $7.46 $34]
foreach receipt receipts [
    if (receipt > highest) and (receipt < $50) [highest: receipt] 
]
alert rejoin ["Maximum receipt below fifty bucks: " highest]

3.3 Searching

The "find" function is used to perform simple searches:

REBOL []
names: ["John" "Jane" "Bill" "Tom" "Jen" "Mike"]
if find names "Bill" [alert "Yes, Bill is in the list!"]
if not find names "Paul" [alert "No, Paul is not in the list."]

You can determine the index position of a found item in a list, using the "index?" function:

REBOL []
names: ["John" "Jane" "Bill" "Tom" "Jen" "Mike"]
indx: index? find names "Bill"
print rejoin ["Bill is at position " indx " in the list."]
halt

You can search for text within each item in a list using a foreach loop to search each individual value:

REBOL []
names: ["John" "Jane" "Bill" "Tom" "Jen" "Mike"]
foreach name names [
    if find name "j" [
        print rejoin ["'j' found in " name]
    ]
]
halt

The "find/any" refinement can be used to search for wildcard characters. The "*" character allows for portions of search text to contain random character strings of any length. The "?" character allows for random character searches of a specified length (at specific character positions within a search term):

REBOL []
names: ["OJ" "John" "Joan" "Jan" "Major Bill" "MJO" "Mike"]
foreach name names [
    if find/any name "*jo*" [
        print rejoin ["'jo' found in " name]
    ]
]
print ""
foreach name names [
    if find/any name "j*n" [
        print rejoin ["'j*n' found in " name]
    ]
]
print ""
foreach name names [
    if find/any name "j??n" [
        print rejoin ["'j--n' found in " name]
    ]
]
halt

3.4 Gathering Data, and the "Copy" Function

When collecting ("aggregating") values into a new block, always use the "copy" function to create the new block. You'll need to do this whenever a sub-list or super-list of values is created based upon conditional evaluations performed on data in a base list:

REBOL []
low-receipts: copy []             ; Create blank list with copy [], NOT []
receipts: [$5.23 $95.98 $7.46 $34]
foreach receipt receipts [
    if receipt < $10 [append low-receipts receipt]     ; add to blank list
]
print low-receipts
halt

For example, the following line should should NOT be used (it does not contain the word "copy" when creating a blank list):

low-receipts: []               ; WRONG - should be   low-receipts: COPY []

The same is true when creating blank string values. Use the "copy" function whenever you create an empty text value that you intend to adjust or add to:

REBOL []
names: copy {}                  ; Create blank string with copy {}, NOT {}
people: ["Joan" "George" "Phil" "Jane" "Peter" "Tom"]
foreach person people [
    if find person "e" [
        append names rejoin [person " "]    ; This appends to blank string
    ]
]
print names
halt

3.5 List Comparison Functions

REBOL has a variety of useful built in list comparison functions. You'll use these for determining differences, similarities, and combinations between sets of data:

REBOL []
group1: ["Joan" "George" "Phil" "Jane" "Peter" "Tom"]
group2: ["Paul" "George" "Andy" "Mary" "Tom" "Tom"]
print rejoin ["Group 1: " group1]  
print ""   
print rejoin ["Group 2: " group2]
print newline
print rejoin ["Intersection:           " intersect group1 group2]
print "^/(values shared by both groups)^/^/"  
print rejoin ["Difference:             " difference group1 group2]
print "^/(values not shared by both groups)^/^/"
print rejoin ["Union:                  " union group1 group2]
print "^/(all unique values contained in both groups)^/^/"
print rejoin ["Join:                   " join group1 group2]
print "^/(one group tacked to the end of the other group)^/^/"
print rejoin ["Excluded from Group 2:  " exclude group1 group2]
print "^/(values contained in group1, but not contained in group2)^/^/"
print rejoin ["Unique in Group 2:      " unique group2]
print "^/(unique values contained in group2)"
halt

3.6 Creating Lists From User Input

3.6.1 Creating New Blocks and Adding Values

You can create a new block using the code pattern below. Simply assign variable labels to "copy []":

REBOL []
items: copy []          ; new empty block named "items"
prices: copy []         ; new empty block named "prices"

Add values to new blocks using the "append" function:

REBOL []
items: copy []
prices: copy []
append items "Screwdriver"
append prices "1.99"
append items "Hammer"
append prices "4.99"
append items "Wrench"
append prices "5.99"

Use the "print", "probe", or "editor" functions to view the data in a block. The "print" function simply prints the values in the block. The "probe" function shows the block data structure (square brackets enclosing the values, quotes around text string values, etc.). The "editor" function opens REBOL's built in text editor, with the block structure displayed:

REBOL []
items: copy []
prices: copy []
append items "Screwdriver"
append prices "1.99"
append items "Hammer"
append prices "4.99"
append items "Wrench"
append prices "5.99"

editor items
editor prices

print rejoin ["ITEMS:   " items newline]
print rejoin ["PRICES:  " prices newline]

probe items
probe prices

halt

3.6.2 Accepting Data Input from a User

You've already been introduced to the "request-text" function. It accepts text input from a user:

REBOL []
request-text

You can assign a variable label to the data entered by the user, and then use that data later in your program:

REBOL []
price: request-text
alert price

You can add a text title to the request-text function, with the "/title" refinement:

REBOL []
price: request-text/title "Input a dollar value:"
alert price

You can add a default text response using the "/default" refinement:

REBOL []
price: request-text/default "14.99"
alert price

You can combine the "/title" and "/default" refinements:

REBOL []
price: request-text/title/default "Input a dollar value:" "14.99"
alert price

The "ask" function does the same thing, but within the text environment of the REBOL interpreter console (instead of using a popup windowed requestor):

REBOL []
price: ask "Input a dollar value:  $"
alert price

3.6.3 Building Blocks from User-Entered Data

Add data to a block, which has been entered by the user, using the code pattern below. Append the variable label of the entered data to the block label:

REBOL []
items: copy []
prices: copy []
item: request-text/title/default "Item:" "screwdriver"
price: request-text/title/default "Price:" "1.99"
append items item
append prices price

The example below uses a "forever" loop to repeatedly perform the "request-text" and "append" operations. A conditional "if" evaluation checks to see if the user enters "" (empty text) in the Item requestor. If so, it stops the forever loop using the "break" function, and displays the data in each block:

REBOL []
items: copy []
prices: copy []
forever [
    item: request-text/title "Item:"
    if item = "" [break]
    price: request-text/title "Price:"
    append items item
    append prices price
]
print "Items:^/"                       ; THE ^/ CHARACTER PRINTS A NEWLINE
probe items
print "^/^/Prices:^/"
probe prices
halt

You could just as easily add the entered data to a single block:

REBOL []
inventory: copy []
forever [
    item: request-text/title "Item:"
    if item = "" [break]
    price: request-text/title "Price:"
    append inventory item
    append inventory price
]
print "Inventory:^/"
probe inventory
halt

3.6.4 Saving and Reading Block Data To/From Files

Save a block to a text file using the "save" function. Remember that in REBOL, file names always begin with the "%" character:

REBOl []
inventory: ["Screwdriver" "1.99" "Hammer" "4.99" "Wrench" "5.99"]
save %inv.txt inventory
alert "Saved"

Load blocked data from a saved file using the "load" function. You can assign a variable label to the loaded data, to use it later in the program:

REBOL []
inventory: load %inv.txt
print "Inventory^/"
probe inventory
halt

You can also append data directly to a file using the "write/append" function. When using the "write/append" function, use the "mold" function to enclose each text value in quotes, and the "rejoin" function to separate each value with a space:

REBOL []
forever [
    item: request-text/title "Item:"
    if item = "" [break]
    price: request-text/title "Price:"
    write/append %inv.txt rejoin [
        mold item " " mold price " "
    ]
]
inventory: load %inv.txt
print "Inventory:^/"
probe inventory
halt

3.7 Three Useful Data Storage Programs: Inventory, Contacts, Schedule

The last program above provides a nice template for practical applications of all types. It stores and displays inventory items and prices. Notice that a "title" variable has been added to the header, set to the text "Inventory". It's good practice to assign titles to all your programs:

REBOL [title: "Inventory"]
forever [
    item: request-text/title "Item:"
    if item = "" [break]
    price: request-text/title "Price:"
    write/append %inv.txt rejoin [
        mold item " " mold price " "
    ]
]
inventory: load %inv.txt
print "Inventory:^/"
probe inventory
halt

Here's the same program as above, changed slightly to store and display contact information:

REBOL [title: "Contacts"]
forever [
    name: request-text/title "Name:"
    if name = "" [break]
    address: request-text/title "Address:"
    phone: request-text/title "Phone:"
    write/append %contacts.txt rejoin [
        mold name " " mold address " " mold phone " "
    ]
]
contacts: load %contacts.txt
print "Contacts:^/"
probe contacts
halt

Here it is again, repurposed to hold schedule information:

REBOL [title: "Schedule"]
forever [
    event: request-text/title/default "Event Title:" "Meeting with "
    if event = "" [break]
    date: request-text/title/default "Date:" "1-jan-2013"
    time: request-text/title/default "Time:" "12:00pm"
    notes: request-text/title/default "Notes:" "Bring: "
    write/append %schedule.txt rejoin [
        mold event " " mold date " " mold time " " mold notes " "
    ]
]
schedule: load %schedule.txt
print "Schedule:^/^/"
probe schedule
halt

The types of data you store using these sorts of operations can be adjusted specifically to your particular data management needs for any given task. Your ability to apply this code to practical situations is limited only by your own creativity. All you need to do is change the requestor titles and the variable labels to clarify the type of data being stored.

3.8 Working With Tables of Data: Columns and Rows

Columns within tables of data are arranged in sequential order in blocks. Indentation and white space helps to display columns neatly, within a visual "table" layout. The following table conceptually contains 3 rows of 3 columns of data, but the whole block is still just a sequential list of 9 items:

accounts:  [
    "Bob"   $529.23   21-jan-2013
    "Tom"   $691.37   13-jan-2013
    "Ann"   $928.85   19-jan-2013
]

The foreach function in the next example alerts the user with every three consecutive data values in the table (each row of 3 consecutive name, balance, and date column values):

REBOL []
accounts:  [
    "Bob" $529.23 21-jan-2013
    "Tom" $691.37 13-jan-2013
    "Ann" $928.85 19-jan-2013
]
foreach [name balance date] accounts [
    alert rejoin [
        "Name: " name ", Date: " date ", Balance: " balance
    ]
]

This example displays the computed balance for each person on the given date. The amount displayed is the listed "balance" value for each account, minus a universal "fee" value):

REBOL []
accounts:  [
    "Bob" $529.23 21-jan-2013
    "Tom" $691.37 13-jan-2013
    "Ann" $928.85 19-jan-2013
]
fee: $5
foreach [name balance date] accounts [
    alert rejoin [name "'s balance on " date " will be " balance - fee]
]

Here's a variation of the above example which displays the sum of values in all accounts:

REBOL []
accounts:  [
    "Bob" $529.23 21-jan-2013
    "Tom" $691.37 13-jan-2013
    "Ann" $928.85 19-jan-2013
]
sum: $0
foreach [name balance date] accounts [sum: sum + balance]
alert rejoin ["The total of all balances is: " sum]

Here's a variation that computes the average balance:

REBOL []
accounts:  [
    "Bob" $529.23 21-jan-2013
    "Tom" $691.37 13-jan-2013
    "Ann" $928.85 19-jan-2013
]
sum: $0
foreach [name balance date] accounts [sum: sum + balance]
alert rejoin [
    "The average of all balances is: " 
    sum / ((length? accounts) / 3)
]

Here is a variation of the "Schedule" application from the previous section, slightly adjusted using the "foreach" function to format a more cleanly printed data display:

REBOL []
forever [
    event: request-text/title "Event Title:"
    if event = "" [break]
    date: request-text/title/default "Date:" "1-jan-2013"
    time: request-text/title/default "Time:" "12:00pm"
    notes: request-text/title/default "Notes:" "Bring: "
    write/append %schedule.txt rejoin [
        mold event " " mold date " " mold time " " mold notes " "
    ]
]
schedule: load %schedule.txt
print newpage                          ; "newpage" prints a cleared screen
print "SCHEDULE:^/^/"
foreach [event date time notes] schedule [
    print rejoin [
        "Event:  " event newline
        "Date:   " date newline
        "Time:   " time newline
        "Notes:  " notes newline newline
    ]
]
halt

Here is the "Inventory" program from the previous section, adjusted slightly to count the number of items and calculate a sum of inventory prices:

REBOL [title: "Inventory"]
forever [
    item: request-text/title "Item:"
    if item = "" [break]
    price: request-text/title "Price:"
    write/append %inv.txt rejoin [
        mold item " " mold price " "
    ]
]
inventory: load %inv.txt
count: 0
sum: $0
foreach [item price] inventory [
    count: count + 1
    sum: sum + to-money price
]
print newpage
print rejoin ["Total # of Items:  " count]
print rejoin ["Sum of Prices:     " sum]
halt

Here's a variation of the "Contacts" application that searches for saved names, and prints out any matching contact information:

REBOL []
search: request-text/title/default "Search text:" "John"
contacts: load %contacts.txt
print newpage
print rejoin [search " found in:^/"]
foreach [name address phone] contacts [
    if find name search [
        print rejoin [
            "Name:      " name newline
            "Address:   " address newline
            "Phone:     " phone newline
        ]
    ]
]
halt

The ability to conceptually "flatten" tabular data into sequential streams of items, and vice-versa, to think of consecutive groups of items in a list as rows within mapped categorical columns, is fundamentally important to working with all sorts of business data sets. You'll see this concept applied regularly throughout examples in this tutorial and in real working code.

3.9 Additional List/Block/Series Functions and Techniques

REBOL has built-in functions for performing every imaginable manipulation to list content, order, and other block properties - adding, deleting, searching, sorting, comparing, counting, replacing, changing, moving, etc. Here's a quick demonstrative list of functions. Try pasting each line individually into the REBOL interpreter to see how each function works:

REBOL []

names: ["John" "Jane" "Bill" "Tom" "Jen" "Mike"]  ; a list of text strings

print "Two ways of printing values, 'probe' and 'print':"
probe names   ; "Probe" is like "print", but it shows the actual data
print names   ;  structure. "Print" attempts to format the displayed data.

print "^/Sorting:"
sorted: sort copy names    ; "Sort" sorts values ascending or descending.
probe names                ; "Copy" keeps the names block from changing
print sorted
sort/reverse names         ; Here, the names block has been sorted without
probe names                ; copy, so it's permanently changed.

print "^/Picking items:"
probe first names                 ; 3 different ways to pick the 1st item:
probe names/1 
probe pick names 1 
probe second names                ; 3 different ways to pick the 2nd item:
probe names/2
probe pick names 2

print "^/Searching:"
probe find names "John"                            ; How to search a block
probe first find names "John"
probe find/last names "Jane"
probe select names "John"                    ; Find next item after "John"

print "^/Taking sections of a series:"
probe at names 2
probe skip names 2                                  ; Skip every two items
probe extract names 3                           ; Collect every third item

print "^/Making changes:"
append names "George"
probe names
insert (at names 3) "Lee" 
probe names
remove names
probe names 
remove find names "Mike" 
probe names
change names "Phil" 
probe names
change third names "Phil"
probe names
poke names 3 "Phil" 
probe names
probe copy/part names 2 
replace/all names "Phil" "Al"
probe names

print "^/Skipping around:"
probe head names 
probe next names 
probe back names 
probe last names 
probe tail names  
probe index? names 

print "^/Converting series blocks to strings of text:"
probe form names
probe mold names

print "^/Other Series functions:"
print length? names 
probe reverse names 
probe clear names
print empty? names
halt

To demonstrate just a few of the functions above, here are some practical examples of common list operations, performed on a block of user contact information. The demonstration block of data is organized as 5 rows of 3 columns of data (name, address, phone), or 15 consecutive items in a list labeled "users". Notice that to maintain the column and row structure, empty strings ("") are placed at positions in the list where there is no data:

REBOL []
users: [
    "John Smith" "123 Tomline Lane Forest Hills, NJ" "555-1234"
    "Paul Thompson" "234 Georgetown Pl. Peanut Grove, AL" "555-2345"
    "Jim Persee" "345 Pickles Pike Orange Grove, FL" "555-3456"
    "George Jones" "456 Topforge Court Mountain Creek, CO" ""
    "Tim Paulson" "" "555-5678"
]

append users ["Joe Thomas" "" "555-321-7654"]  ; append to end of list
probe users

probe (at users 4)                      ; parentheses are not required

insert (at users 4) [
    "Tom Adams" "321 Way Lane Villageville, AZ" "555-987-6543"
]
probe users

remove (at users 4)                                   ; remove 1 item
probe users

; BE CAREFUL - the line above breaks the table structure by removing
; an item entirely, so all other data items are shifted into incorrect
; columns.  Instead, either replace the data with an empty place holder
; or remove the address and phone fields too:

remove/part (at users 4) 2                            ; remove 2 items
probe users

change (at users 1) "Jonathan Smith"
probe users

remove (at users 1) insert (at users 1) "Jonathan Smith"
probe users
halt

The "extract" function is useful for picking out columns of data from structured blocks:

REBOL []
users: [
    "John Smith" "123 Tomline Lane Forest Hills, NJ" "555-1234"
    "Paul Thompson" "234 Georgetown Pl. Peanut Grove, AL" "555-2345"
    "Jim Persee" "345 Pickles Pike Orange Grove, FL" "555-3456"
    "George Jones" "456 Topforge Court Mountain Creek, CO" ""
    "Tim Paulson" "" "555-5678"
] 
probe extract users 3             ; names
probe extract (at users 2) 3      ; addresses 
probe extract (at users 3) 3      ; phone numbers 
halt

You can "pick" items at a particular index location in the list:

REBOL []
users: [
    "John Smith" "123 Tomline Lane Forest Hills, NJ" "555-1234"
    "Paul Thompson" "234 Georgetown Pl. Peanut Grove, AL" "555-2345"
    "Jim Persee" "345 Pickles Pike Orange Grove, FL" "555-3456"
    "George Jones" "456 Topforge Court Mountain Creek, CO" ""
    "Tim Paulson" "" "555-5678"
]
print pick users 1                  ; FIRST name
print pick users 2                  ; FIRST address
print pick users 3                  ; FIRST phone
;
print pick users 4                  ; SECOND name
print pick users 5                  ; SECOND address
print pick users 6                  ; SECOND phone
;
indx: length? users                 ; index position of the LAST item
print pick users indx               ; last item
print pick users (indx - 1)         ; second to last item
print pick users (random length? users)  ; random item
halt

You can determine the index location at which an item is found, using the "find" function:

indx: index? find users "John Smith"

In REBOL there 4 ways to pick items at such a variable index. Each syntax below does the exact same thing. These are just variations of the "pick" syntax:

print pick users indx
print users/:indx
print compose [users/(indx)]       ; put composed values in parentheses
print reduce ['users/(indx)]       ; put a tick mark on non-reduced values

Pay particular attention to the "compose" and "reduce" functions. They allow you to convert static words in blocks to evaluated values:

REBOL []

; This example prints "[month]" 12 times:

foreach month system/locale/months [
    probe [month]
]

; These examples print all 12 month values:

foreach month system/locale/months [
    probe reduce [month]
]

foreach month system/locale/months [
    probe compose [(month)]
]

Here's a complete example that requests a name from the user, finds the index of that name in the list, and picks out the name, address, and phone data for that user (located at the found indx, indx + 1, and indx + 2 positions):

REBOL [title: "Search Users"]
users: [
    "John Smith" "123 Tomline Lane Forest Hills, NJ" "555-1234"
    "Paul Thompson" "234 Georgetown Pl. Peanut Grove, AL" "555-2345"
    "Jim Persee" "345 Pickles Pike Orange Grove, FL" "555-3456"
    "George Jones" "456 Topforge Court Mountain Creek, CO" ""
    "Tim Paulson" "" "555-5678"
]

name: request-text/title/default "Name:" "Jim Persee"
indx: index? find users name

print rejoin [
    (pick users indx) newline
    (pick users (indx + 1)) newline
    (pick users (indx + 2)) newline
]
halt

Here's a version that uses code from the "Contacts" program you saw earlier. It allows you to create your own user database, and then search and display entries with the code above:

REBOL [title: "Search My Stored Contacts"]

; This code is borrowed from the "Contacts" program seen earlier:

forever [
    name: request-text/title "Name:"
    if name = "" [break]
    address: request-text/title "Address:"
    phone: request-text/title "Phone:"
    write/append %contacts.txt rejoin [
        mold name " " mold address " " mold phone " "
    ]
]
users: load %contacts.txt

; This is a variation of the code above which adds an error check, to
; provide a response if the search text is not found in the data block:

name: request-text/title/default "Search For:" "Jim Persee"
if error? try [indx: index? find users name] [
    alert "Name not found" quit
]
print rejoin [
    (pick users indx) newline
    (pick users (indx + 1)) newline
    (pick users (indx + 2)) newline
]
halt

3.10 Sorting Lists and Tables of Data

You can sort a list of data using the "sort" function:

REBOL []
print sort system/locale/months
halt

This example displays a list requestor with the months sorted alphabetically:

REBOL []
request-list "Sorted months:" sort system/locale/months

If you sort a block of values consisting of data types that REBOL understands, the values will be sorted appropriately for their type (i.e., chronologically for dates and times, numerically for numbers, alphabetically for text strings):

REBOL []
probe sort [1 11 111 2 22 222 8 9 5]  ; sorted NUMERICALLY
probe sort ["1" "11" "111" "2" "22" "222" "8" "9" "5"]  ; ALPHABETICALLY
probe sort [1-jan-2012 1-feb-2012 1-feb-2011]  ; sorted CHRONOLOGICALLY
halt

To sort by the first column in a table, use the "sort/skip" refinement. The table below is made up of 5 rows of 3 conceptual columns, so the first item of each row is found by skipping every 3 values:

REBOL []
users: [
    "John Smith" "123 Tomline Lane Forest Hills, NJ" "555-1234"
    "Paul Thompson" "234 Georgetown Pl. Peanut Grove, AL" "555-2345"
    "Jim Persee" "345 Pickles Pike Orange Grove, FL" "555-3456"
    "George Jones" "456 Topforge Court Mountain Creek, CO" ""
    "Tim Paulson" "" "555-5678"
]
editor sort/skip users 3

Sorting by any other selected column requires that data be restructured into blocks of blocks which clearly define the column structure. For example, this "flat" table, although visually clear, is really just a consecutive list of 15 data items:

users: [
    "John Smith" "123 Tomline Lane Forest Hills, NJ" "555-1234"
    "Paul Thompson" "234 Georgetown Pl. Peanut Grove, AL" "555-2345"
    "Jim Persee" "345 Pickles Pike Orange Grove, FL" "555-3456"
    "George Jones" "456 Topforge Court Mountain Creek, CO" ""
    "Tim Paulson" "" "555-5678"
]

To sort it by colomn, the data must be represented as follows (notice that conceptual rows are now separated into discrete blocks of 3 columns of data):

blocked-users: [
    ["John Smith" "123 Tomline Lane Forest Hills, NJ" "555-1234"]
    ["Paul Thompson" "234 Georgetown Pl. Peanut Grove, AL" "555-2345"]
    ["Jim Persee" "345 Pickles Pike Orange Grove, FL" "555-3456"]
    ["George Jones" "456 Topforge Court Mountain Creek, CO" ""]
    ["Tim Paulson" "" "555-5678"]
]

The following code demonstrates how to convert a flattened block into such a structure of nested row/column blocks:

REBOL []
users: [
    "John Smith" "123 Tomline Lane Forest Hills, NJ" "555-1234"
    "Paul Thompson" "234 Georgetown Pl. Peanut Grove, AL" "555-2345"
    "Jim Persee" "345 Pickles Pike Orange Grove, FL" "555-3456"
    "George Jones" "456 Topforge Court Mountain Creek, CO" ""
    "Tim Paulson" "" "555-5678"
]
blocked-users: copy []
foreach [name address phone] users [
    ; APPEND/ONLY inserts blocks as blocks, instead of as individual items
    ; The REDUCE function convert the words "name", "address", and "phone"
    ; to text values:
    append/only blocked-users reduce [name address phone]
]
editor blocked-users

Now you can use the "/compare" refinement of the sort function to sort by a chosen column (field):

REBOL []
blocked-users: [
    ["John Smith" "123 Tomline Lane Forest Hills, NJ" "555-1234"]
    ["Paul Thompson" "234 Georgetown Pl. Peanut Grove, AL" "555-2345"]
    ["Jim Persee" "345 Pickles Pike Orange Grove, FL" "555-3456"]
    ["George Jones" "456 Topforge Court Mountain Creek, CO" ""]
    ["Tim Paulson" "" "555-5678"]
]
field: 2                          ; column to sort (address, in this case)
sort/compare blocked-users func [a b] [(at a field) < (at b field)]
editor blocked-users                ; sorted by the 2nd field (by address)

To sort in the opposite direction (i.e., descending, as opposed to ascending), just change the "<" operater to ">":

REBOL []
blocked-users: [
    ["John Smith" "123 Tomline Lane Forest Hills, NJ" "555-1234"]
    ["Paul Thompson" "234 Georgetown Pl. Peanut Grove, AL" "555-2345"]
    ["Jim Persee" "345 Pickles Pike Orange Grove, FL" "555-3456"]
    ["George Jones" "456 Topforge Court Mountain Creek, CO" ""]
    ["Tim Paulson" "" "555-5678"]
]
field: 2
sort/compare blocked-users func [a b] [(at a field) > (at b field)]
editor blocked-users

Here's a complete example that converts a flat data block to a nested block of blocks, and then sorts by a user-selected field, in a chosen ascending/descending direction:

REBOL [title: "View Sorted Users"]
users: [
    "John Smith" "123 Tomline Lane Forest Hills, NJ" "555-1234"
    "Paul Thompson" "234 Georgetown Pl. Peanut Grove, AL" "555-2345"
    "Jim Persee" "345 Pickles Pike Orange Grove, FL" "555-3456"
    "George Jones" "456 Topforge Court Mountain Creek, CO" ""
    "Tim Paulson" "" "555-5678"
]
blocked-users: copy []
foreach [name address phone] users [
    append/only blocked-users reduce [name address phone]
]
field: to-integer request-list "Choose Field To Sort By:" ["1" "2" "3"]
order: request-list "Ascending or Descending:" ["ascending" "descending"]
either order = "ascending" [
    sort/compare blocked-users func [a b] [(at a field) < (at b field)]
][
    sort/compare blocked-users func [a b] [(at a field) > (at b field)]
]
editor blocked-users

Here's a version of the program above that uses code from the "Contacts" app presented earlier, which allows you to enter your own "users" contact info, and then sort and display it as above:

REBOL [title: "Sort My Stored Contacts"]

; This code is borrowed from the "Contacts" program seen earlier:

forever [
    name: request-text/title "Name:"
    if name = "" [break]
    address: request-text/title "Address:"
    phone: request-text/title "Phone:"
    write/append %contacts.txt rejoin [
        mold name " " mold address " " mold phone " "
    ]
]
users: load %contacts.txt

; This is a variation of the code above:

blocked-users: copy []
foreach [name address phone] users [
    append/only blocked-users reduce [name address phone]
]
field-name: request-list "Choose Field To Sort By:" [
    "Name" "Address" "Phone"
]

; The "select" function chooses the next value in a list, selected by the
; user.  In this case if the field-name variable equals "name", the
; "field" variable is set to 1.  If the field-name variable equals
; "address", the "field" variable is set to 2.  If field-name="phone", the
; "field" variable is set to 3:

field: select ["name" 1 "address" 2 "phone" 3] field-name

order: request-list "Ascending or Descending:" ["ascending" "descending"]
either order = "ascending" [
    sort/compare blocked-users func [a b] [(at a field) < (at b field)]
][
    sort/compare blocked-users func [a b] [(at a field) > (at b field)]
]
editor blocked-users

Note again that REBOL sorts data appropriately, according to type. If numbers, dates, times, and other recognized data types are stored as string values, the sort will be alphabetical for the chosen field (because that is the appropriate sort order for text):

REBOL []
text-data: [
    "1"    "1-feb-2012"  "1:00am"   "abcd"
    "11"   "1-mar-2012"  "1:00pm"   "bcde"
    "111"  "1-feb-2013"  "11:00am"  "cdef"
    "2"    "1-mar-2013"  "13:00"    "defg"
    "22"   "2-feb-2012"  "9:00am"   "efgh"
    "222"  "2-feb-2009"  "11:00pm"  "fghi"
]
blocked: copy []
foreach [number date time string] text-data [
    append/only blocked reduce [number date time string]
]
field-name: request-list "Choose Field To Sort By:" [
    "number" "date" "time" "string"
]
field: select ["number" 1 "date" 2 "time" 3 "string" 4] field-name
order: request-list "Ascending or Descending:" ["ascending" "descending"]
either order = "ascending" [
    sort/compare blocked func [a b] [(at a field) < (at b field)]
][
    sort/compare blocked func [a b] [(at a field) > (at b field)]
]
editor blocked

Convert values to appropriate data types during the process of blocking the "flattened" data, and fields will magically be sorted appropriately (in numerical, chronological, or other data-type-appropriate order):

REBOL []
text-data: [
    "1"    "1-feb-2012"  "1:00am"   "abcd"
    "11"   "1-mar-2012"  "1:00pm"   "bcde"
    "111"  "1-feb-2013"  "11:00am"  "cdef"
    "2"    "1-mar-2013"  "13:00"    "defg"
    "22"   "2-feb-2012"  "9:00am"   "efgh"
    "222"  "2-feb-2009"  "11:00pm"  "fghi"
]
blocked: copy []
foreach [number date time string] text-data [
    append/only blocked reduce [
        to-integer number
        to-date date
        to-time time
        string
    ]
]
field-name: request-list "Choose Field To Sort By:" [
    "number" "date" "time" "string"
]
field: select ["number" 1 "date" 2 "time" 3 "string" 4] field-name
order: request-list "Ascending or Descending:" ["ascending" "descending"]
either order = "ascending" [
    sort/compare blocked func [a b] [(at a field) < (at b field)]
][
    sort/compare blocked func [a b] [(at a field) > (at b field)]
]
editor blocked

3.11 CSV Files and the "Parse" Function

"Comma Separated Value" (CSV) files are a universal text format used to store and transfer tables of data. Spreadsheets, database systems, financial software, and other business applications typically can export and import tabular data to and from CSV format.

In CSV files, rows of data are separated by a line break. Column values are most often enclosed in quotes and separated by a comma or other "delimiter" character (sometimes a tab, pipe (|), or other symbol that visually separates the values).

3.11.1 Saving Tabular Data Blocks to CSV Files

You can create a CSV file from a block of REBOL table data, using the "foreach" function. Just rejoin each molded value (value enclosed in quotes), with commas separating each item, and a newline after each row, into a long text string. Then save the string to a file with the extension ".csv":

REBOL [title: "Save CSV"]
users: [
    "John Smith" "123 Tomline Lane Forest Hills, NJ" "555-1234"
    "Paul Thompson" "234 Georgetown Pl. Peanut Grove, AL" "555-2345"
    "Jim Persee" "345 Pickles Pike Orange Grove, FL" "555-3456"
    "George Jones" "456 Topforge Court Mountain Creek, CO" ""
    "Tim Paulson" "" "555-5678"
]
foreach [name address phone] users [
    write/append %users.csv rejoin [
        mold name ", " mold address ", " mold phone newline
    ]
]

Try opening the file above with Excel or another spreadsheet application. Because the particular values in this data block contain commas within the address field, you may need to select "comma", "space", and "merge delimiters", or similar options, in programs such as OpenOffice Calc.

3.11.2 Loading Tabular Data Blocks From CSV Files

To import CSV files into REBOL, use the "read/lines" function to read the file contents, with one text line per item stored in the resulting block. Assign the results of the read/lines function to a variable label. Use "foreach" and REBOL's "parse" function to separate each item in the lines back to individual values. Collect all the resulting sequential values into an empty block, and you're ready to use the data in all the ways you've seen so far:

REBOL [title: "Load CSV - Flat"]
block: copy []
csv: read/lines %users.csv
foreach line csv [
    data: parse line ","
    append block data
]
probe block
foreach [name address phone] block [
    alert rejoin [name ": " address " " phone]
]
halt

The first parameter of the parse function is the data to be parsed (in the case above, each line of the CSV file). The second parameter is the delimiter character(s) used to separate each value. Assign a variable to the output of the parse function, and you can refer to each individual value as needed (using "pick" and other series functions). The code above creates a "flat" block. To create a block of blocks, in which each line of the CSV file is delineated into a separate interior (nested) block, just use the append/only function, as you've seen earlier:

REBOL [title: "Load CSV - Block of Blocks"]
block: copy []
csv: read/lines %users.csv
foreach line csv [
    data: parse line ","
    append/only block data
]
probe block
foreach line block [probe line]
halt

Parse's "/all" refinement can be used to control how spaces and other characters are treated during the text splitting process (for example, if you want to separate the data at commas contained within each quoted text string). You can use the "trim" function to eliminate extra spaces in values. Other functions such as "replace", "to-(value)", and conditional evaluations, for example, can be useful in converting, excluding, and otherwise processing imported CSV data.

Try downloading account data from Paypal, or export report values from your financial software, and you'll likely see that the most prominent format is CSV. Accountants and others who use spreadsheets to crunch numbers will be able to instantly use CSV files in Excel, and/or export worksheet data to CSV format, for you to import and use in REBOL programs.

You'll learn much more about the extremely powerful "parse" function later. For now, it provides a simple way to import data stored in the common CSV format.

3.12 Two Paypal Report Programs, Analyzed

Take a look at the Paypal code examples you've seen so far in this text. You should be able to follow the code a bit now:

REBOL [title: "Paypal Report"]

; A variable used to calculate the sum is initially set to zero dollars:

sum: $0

; A foreach loop goes through every line in the downloaded CSV file,
; starting at the second line (the first line contains columns labels):

foreach line (at (read/lines http://re-bol.com/Download.csv) 2) [

    ; The sum is computed, using the money value in column 8:

    sum: sum + to-money pick (parse/all line ",") 8

]

; The user is alerted with the total:

alert form sum

Here's the whole program, without comments:

REBOL [title: "Paypal Report"]
sum: $0
foreach line (at (read/lines http://re-bol.com/Download.csv) 2) [
    sum: sum + to-money pick (parse/all line ",") 8
]
alert form sum

This example deals with several different columns, and performs conditional evaluations on the name and time fields:

REBOL [title: "Paypal Reports"]

; Variables used to calculate 2 different sums are initially set to $0:

sum1: sum2: $0

; A foreach loop goes through every line in the downloaded CSV file,
; starting at the second line (the first line contains columns labels):

foreach line at read/lines http://re-bol.com/Download.csv 2 [

    ; The first sum is computed, using the money value in column 8:

    sum1: sum1 + to-money pick row: parse/all line "," 8

    ; If the name column (col #4) contains the text "Saoud", print a
    ; a concatenated message.  That message text consists of the date
    ; (column 1), the characters ", Saoud Gorn: ", and the money value
    ; in column 8:

    if find row/4 "Saoud" [print rejoin [row/1 ", Saoud Gorn: " row/8]]

    ; If the name column contains "Ourliptef.com", then perform an
    ; additional conditional evaluation checking if the time field value
    ; (column 2) is between midnight and noon.  If so, add to the sum2
    ; variable the money value in column 8:

    if find row/4 "Ourliptef.com" [
        time: to-time row/2
        if (time >= 0:00am) and (time <= 12:00pm) [
            sum2: sum2 + to-money row/8
        ]
    ]

]

; Alert the user with some concatenated messages displaying the sums:

alert join "GROSS ACCOUNT TRANSACTIONS: " sum1
alert join "2012 Ourliptef.com Morning Total: " sum2

Here's the whole program, without comments:

REBOL [title: "Paypal Reports"]
sum1: sum2: $0
foreach line at read/lines http://re-bol.com/Download.csv 2 [
    sum1: sum1 + to-money pick row: parse/all line "," 8
    if find row/4 "Saoud" [print rejoin [row/1 ", Saoud Gorn: " row/8]]
    if find row/4 "Ourliptef.com" [
        time: to-time row/2
        if (time >= 0:00am) and (time <= 12:00pm) [
            sum2: sum2 + to-money row/8
        ]
    ]
]
alert join "GROSS ACCOUNT TRANSACTIONS: " sum1
alert join "2012 Ourliptef.com Morning Total: " sum2

To see the data these scripts are sorting through, take a look at the raw data in the Download.csv file.

3.13 Some Perspective about Studying These Topics

The List and Table Data topics are the most difficult sections in the first half of the tutorial. They will likely require several readings to be fully understood. Start by skimming once, and become familiar with the basic language structures and general code patterns. During the first read, you should be aware that demonstrated functions and code snippets can simply be copied, altered, and pasted for use in other applications. You don't need to memorize or even thoroughly understand how each line of code works. Instead, it's more important to understand that the functions and block/table concepts contained here simply exist and produce the described results. You will learn and interalize the details only by rote, through an extended period of reading, studying, copying, altering, and eventually writing fluently. There is a lot of material here to consume. It will likely take numerous applied hours of coding to fully understand it all.

You may find small snippets of code which provide solutions for the initial problem(s) and curiosities that motivated you to "learn how to program". Spend extra time experimenting with those pieces of code that are most interesting and relevant to your immediate needs. Copy, paste, and run examples in the REBOL interpreter. Get used to editing and altering pieces of code to become more familiar with the syntax. Change variable labels, enter new data values, and try repurposing code examples to fit new data sets. Try to break working code and figure out how to fix it. Get used to USING the REBOL text editor and the interpreter console. Get your hands dirty and bury yourself in the mechanics of typing and running code. Becoming comfortable with the tool set and working environment is huge part of the battle.

You will learn REBOL and all other programming languages in the exact same way you would learn any spoken language: by "speaking" it. You must mimic at first (copy/paste code), and then learn to put together "phrases" that make sense (edit, experiment, and rearrange words), and eventually write larger compositions fluently. You will regularly make mistakes with function syntax as you learn to code, just as children make mistakes with grammar as they learn to speak. You'll only learn by experimenting creatively, and by experiencing errors.

It's important not to let initial confusion and error stop you from learning at this point. Use the materials in this section as a reference for looking up functions and syntax as you progress through the tutorial. Try to understand some key points about the structure of the language, especially the code patterns related to block and table operations, but realize that you'll only internalize so much detail during your first read. Acquire as much understanding and experiment with code as much as your curiosity and motivation allows, then move on and see how other important topics fit together to form useful coding skills.

Once you've made it past the next few sections, and in particular the complete programs section, you will have gotten a solid overview of how all the fundamental concepts are put to use. It's a good idea to review the entire first part of the tutorial at that point, paying closer attention to the fine details of each line of code, memorizing functions, immersing yourself in the logic of each word's operation, etc. For now, read and understand the general conceptual overview, and try not to get stuck on any single topic.

For more information about using lists and tables of data in REBOL, see http://www.rebol.com/docs/core23/rebolcore-6.html.

4. Using GUI Windows and Widgets to Input and Display Data

You've already seen how a number of functions can be used to display and request information from the user (print, request-text, request-list, editor, etc.). For simple utilities, these input/output functions are often all that's needed to build functional scripts. To create more complex programs that allow for both increasingly complex data entry, and increased ease of use, "GUI" or Graphic User Interfaces are typically employed. GUIs are windows, forms, and data entry screens that typically contain "widgets" such as text fields, buttons, drop down selectors, multi-line text areas, data grids, menus, and other recognizable visual components. The requestors you've seen so far are very simple types of GUIs, but they only accept single units of data. Windowed GUIs allow users to view and edit multiple fields of data on a single screen. This tends to be more efficient and less error prone than responding to sequential requests for input, and is the "normal" interface expected by users of business applications. GUI coding requires quite a bit of core knowledge in most programming languages. REBOL makes it easy (in fact, REBOL provides absolutely the simplest way to create GUIs with code).

4.1 Basic Layout Guidelines and Widgets

To create a program window, paste the the following code into the REBOL editor and press [F5] to save and run:

REBOL []
view layout [size 600x440]

To center a program window on your computer screen, use "center-face"

REBOL []
view center-face layout [size 600x440]

You can put a title in your program header, which will appear in the title bar of your program window:

REBOL [title: "My Program"]
view center-face layout [size 600x440]

By default, REBOL program windows have a gray backdrop. You can change that using the "backdrop" word:

REBOL [title: "My Program"]
view center-face layout [size 600x440  backdrop white]

Instead of the "backdrop" word, you can use the following code to change the default color for all items in a GUI. This provides a slightly cleaner feel than REBOL's default grey color:

svv/vid-face/color: white

Here's how you add "widgets" (buttons, text fields, multi-line text areas, drop down lists, etc.) to your program window. Notice that everything in the GUI window code is still contained between square brackets, but it has all been indented 4 spaces. Indentation is not required for multi-line block sections, but makes the code easier to read, and is expected. Notice also that the window sizes automatically to fit the contained widgets:

REBOL [title: "My Program"]
svv/vid-face/color: white
view center-face layout [
    field "Type Here"
    area "Multi^/line^/text"
    text-list data ["first" "second" "third"]
    image logo.gif   ; this image is built into REBOL
    btn "Click Me"
]

You can adjust the size, color, and other properties of a widget by including modifiers next to each widget. Notice the GUI window automatically expands to fit resized widgets:

REBOL [title: "My Program"]
svv/vid-face/color: white
view center-face layout [
    field 600 "Type Here"
    area 600 "Multi^/line^/text"
    text-list 600 data ["first" "second" "third"]
    image purple logo.gif
    btn red 100 "Click Me"
]

By default, REBOL places widgets below one another in the program window. You can align widgets horizontally using the "across" word. You can change back to the default vertical positioning with the word "below":

REBOL []
view center-face layout [
    across
    text-list 194
    text-list 194
    text-list 194
    below
    field 600
    area 600
    across
    text "" 368
    btn 50 "First"
    btn 50 "Next"
    btn 50 "Prev"
    btn 50 "Last"
]

You can change the default starting position of widgets placed on screen using the "origin" word, and adjust default spacing using the "space" word:

REBOL []
view center-face layout [
    size 251x251
    origin 0x0
    space 100x100
    across
    btn 50x50
    btn 50x50
    return
    btn 50x50
    btn 50x50
    origin 50x50
    btn 50x50
    btn 50x50
    return
    btn 50x50
    btn 50x50
]

You can place widgets at a specific coordinate using the "at" word:

REBOL []
view center-face layout [
    at 20x50 btn
    at 70x100 btn
    at 130x150 btn
]

4.2 Breathing Life Into GUI Programs - Performing Actions

Put function words in a block (between square brackets) after GUI widgets, and that function's action will be performed whenever the widget is clicked with a mouse, submitted with the keyboard, or otherwise activated. Notice that the word "value" holds the current/selected value in each widget:

REBOL [title: "My Program"]
svv/vid-face/color: white
view center-face layout [
    field "Type Here" [alert value]
    area "Multi^/line^/text" [alert value]
    text-list data ["first" "second" "third"] [alert value]
    image logo.gif [alert "Nice logo"]
    btn "Click Me" [alert "Clicked"]
]

You can give any widget a variable label and change a labeled widget's text using the "/text" refinement, followed by a colon. Whenever you make changes to a window's appearance, you must use the "show" function to update the display:

REBOL []
view layout [
    size 600x400
    field1: field "field 1"  ; this field is labeled "field1"
    btn "change field1's text" [

        ; These actions occur when the button is pressed:

        field1/text: "You just changed field 1's text!"
        show field1
    ]
]

You can read text from a file into a text area, using the "read" function. In REBOL, file names are always preceded by the percent symbol ("%"):

REBOL []
view layout [
    a: area  ; this area is labeled "a"
    btn "Read" [

        ; When btn is clicked, a's text is set to data read from file:

        a/text: read %temp.txt
        show a
    ]
]

You can write text from a text area to a file, using the "write" function:

REBOL []
view layout [
    a: area 
    btn "Save" [

        ; When btn is clicked, write to temp.txt file, the text in area:

        write %temp.txt a/text
        alert "Saved"
    ]
]

IMPORTANT: GUI text fields are only able to display text ("string") values. Note that the following program produces errors because the values returned by the requestors are NOT string values, but rather other data types recognized by REBOL (file, date, tuple, etc. values):

REBOL []
view layout [
    btn "File" [
        f1/text: request-file
        show f1
    ]
    f1: field
    btn "Date" [
        f2/text: request-date  
        show f2
    ]
    f2: field
    btn "Color" [
        f3/text: request-color
        show f3
    ]
    f3: field    
]

When copying formatted text values into a text area, use the "form" function to convert data to a text string:

REBOL []
view layout [
    btn "File" [

        ; when btn pressed, set text of field 1 to selected file name:

        f1/text: form request-file   ; FORM converts file name to text
        show f1
    ]
    f1: field
    btn "Date" [

        ; set text of field 2 to selected date:

        f2/text: form request-date   ; FORM converts date value to text
        show f2
    ]
    f2: field
    btn "Color" [

        ; set text of field 3 to selected color:

        f3/text: form request-color  ; FORM converts color value to text
        show f3
    ]
    f3: field    
]

You can change other properties of a widget, beyond just the text. Change the coordinate position of a widget using the "/offset" refinement, change it's size using the "/size" refinement, just as you alter it's text using the "/text" refinement. The word "face" allows a widget to refer to itself. In the code below, a button widget changes it's own position, size, and text when clicked:

REBOL []
view layout [
    size 594x440 
    btn "click me" [
        face/offset: 200x300
        face/size: 150x50
        face/text: "I've moved and changed!"
        show face 
    ]
]

The "style" word allows you to create new widgets with predefined properties and actions. Here, the label "green-button" is defined as a green btn widget with the text "click me", which when clicked, jumps to a random coordinate within the range 580x420:

REBOL []
view layout [
    size 594x440 

    style green-button btn green "click me" [
        face/offset: random 580x420
        show face
    ]

    ; The word "green-button" now refers to all the above code.  Every
    ; "green-button" shares the same color and text properties, and
    ; PERFORMS THE SAME ACTIONS when clicked.

    at 254x84 green-button
    at 19x273 green-button
    at 85x348 green-button
    at 498x12 green-button
    at 341x385 green-button
]

Here's a little puzzle example, with detailed comments describing the layout and thought processes behind every action in the code:

REBOL [title: "Sliding Puzzle"]

; Create a GUI that's centered on the user's screen:

view center-face layout [

    ; Define some basic layout parameters.  "origin 0x0" 
    ; starts the layout in the upper left corner of the
    ; GUI window.  "space 0x0" dictates that there's no
    ; space between adjacent widgets, and "across" lays
    ; out consecutive widgets next to each other:

    origin 0x0  space 0x0  across 

    ; The section below creates a newly defined button
    ; widget called "piece", with an action block that 
    ; swaps the current button's position with that of 
    ; the adjacent empty space.  That action is run
    ; whenever one of the buttons is clicked:

    style piece button 60x60 [

        ; The lines below check to see if the clicked button
        ; is adjacent to the empty space.  The "offset" 
        ; refinement contains the position of the given 
        ; widget.  The word "face" is used to refer to the
        ; currently clicked widget.  The "empty" button is
        ; defined later (at the end of the GUI layout).
        ; It's ok that the empty button is not yet defined,
        ; because this code is not evaluated until the
        ; the entire layout is built and "view"ed:

        distance: (face/offset - empty/offset)
        if not find [0x60 60x0 0x-60 -60x0] distance [exit]

        ; In English, that reads 'subtract the position of
        ; the empty space from the position of the clicked
        ; button (the positions are in the form of 
        ; Horizontal x Vertical coordinate pairs).  If that 
        ; difference isn't 60 pixels on one of the 4 sides,
        ; then don't do anything.' (60 pixels is the size of
        ; the "piece" button defined above.)

        ; The next three lines swap the positions of the 
        ; clicked button with the empty button.

        ; First, create a variable to hold the current
        ; position of the clicked button:

        temp: face/offset  

        ; Next, move the button's position to that of the 
        ; current empty space:

        face/offset: empty/offset 

        ; Last, move the empty space (button), to the old
        ; position occupied by the clicked button:

        empty/offset: temp
    ]

    ; The lines below draw the "piece" style buttons onto 
    ; the GUI display.  Each of these buttons contains all
    ; of the action code defined for the piece style above:

    piece "1"   piece "2"   piece "3"   piece "4" return
    piece "5"   piece "6"   piece "7"   piece "8" return
    piece "9"   piece "10"  piece "11"  piece "12" return
    piece "13"  piece "14"  piece "15"

    ; Here's the empty space.  Its beveled edge is removed
    ; to make it look less like a movable piece, and more
    ; like an empty space:

    empty: piece 200.200.200 edge [size: 0]
]

Here's the whole program without comments. It's tiny:

REBOL [title: "Sliding Puzzle"]
view center-face layout [    
    origin 0x0 space 0x0 across   
    style piece button 60x60 [
        if not find [0x60 60x0 0x-60 -60x0] (face/offset - e/offset)[exit]
        temp: face/offset
        face/offset: e/offset 
        e/offset: temp
    ]
    piece "1"   piece "2"   piece "3"   piece "4" return
    piece "5"   piece "6"   piece "7"   piece "8" return
    piece "9"   piece "10"  piece "11"  piece "12" return
    piece "13"  piece "14"  piece "15"
    e: piece 200.200.200 edge [size: 0]
]

4.3 GUI Language Reference

Here are all the main GUI words built in to REBOL's GUI dialect (called "VID") that you should get to know. The first block of "styles" contains all the predefined widgets available. The layout words affect how and where items are positioned, and other layout preferences. The attribute words adjust the appearance and function of widgets. The style facets adjust some specific options that are available for individual widgets:

STYLES-WIDGETS: [
    face blank-face IMAGE BACKDROP BACKTILE BOX BAR SENSOR KEY BASE-TEXT
    VTEXT TEXT BODY TXT BANNER VH1 VH2 VH3 VH4 LABEL VLAB LBL LAB TITLE
    H1 H2 H3 H4 H5 TT CODE BUTTON CHECK CHECK-MARK RADIO CHECK-LINE
    RADIO-LINE LED ARROW TOGGLE ROTARY CHOICE DROP-DOWN ICON FIELD INFO
    AREA SLIDER SCROLLER PROGRESS PANEL LIST TEXT-LIST ANIM BTN BTN-ENTER
    BTN-CANCEL BTN-HELP LOGO-BAR TOG
]

LAYOUT-WORDS: [
    return at space pad across below origin guide tab tabs indent style
    styles size backcolor backeffect do
]

STYLE-FACETS--ATTRIBUTES: [
    edge font para doc feel effect effects keycode rate colors texts help
    user-data with bold italic underline left center right top middle
    bottom plain of font-size font-name font-color wrap no-wrap as-is
    shadow frame bevel ibevel
]

SPECIAL-STYLE-FACETS: [
    ARROW: [up right down left]  ROTARY: data  CHOICE: data  DROP-DOWN: 
    [data rows]  FIELD: hide  INFO: hide  AREA: hide  LIST: [supply map
    data]  TEXT-LIST: data  ANIM: [frames rate]
]

You can obtain the word lists above using the following lines of code:

probe extract svv/vid-styles 2
probe remove-each i copy svv/facet-words [function? :i]
probe svv/vid-words

By default, all REBOL GUIs contain the text "REBOL - " in the window title bar. In Windows, you can eliminate that text with the following code. Just set the "tt" variable to hold the title text you want displayed:

tt: "Your Title"
user32.dll: load/library %user32.dll
gf: make routine![return:[int]]user32.dll"GetFocus"
sc: make routine![hw[int]a[string!]return:[int]]user32.dll"SetWindowTextA"
so: :show show: func[face][so[face]hw: gf sc hw tt]

The widgets and techniques you've seen so far are enough to create an overwhelming majority of potentially useful windowed business applications. Here's a collection of useful pieces of code demonstrating how to accomplish various common tasks in GUIs, and some other available widgets. Every piece of code in these examples will be explained in greater detail later in the tutorial. For now, just paste and run these examples to see what they do, and keep the code handy for use when needed:

REBOL [title: "GUI Reference"]
print "GUI Output:^/"
view center-face layout [
    h1 "Some More GUI Widgets:"
    box red 500x2
    drop-down 200 data system/locale/months [
        a/text: join "Month:  " value show a
    ]
    a: field
    slider 200x18 [bar1/data: value show bar1]
    bar1: progress
    scroller 200x16 [bar2/data: value show bar2]
    bar2: progress
    across 
    toggle "Click here" "Click again" [print value]
    rotary "Click" "Again" "And Again" [print value]
    choice "Choose" "Item 1" "Item 2" "Item 3" [print value]
    return
    x: radio y: radio z: radio
    btn "Get Radio States" [print [x/data y/data z/data]]
    return
    led
    arrow
    below
    code "Code text"
    tt "Typewriter text"
    text "Little Text" font-size 8
    title "Centered title" 500
]

; The word "value" refers to data contained in a currently active widget:

view layout [
    text "Some widgets with values and size/color properties.  Try them:"
    button red "Click Me" [alert "You clicked the red button."]
    f: field 400 "Type some text here, then press the [Enter] key" [
        alert value                 ; SAME AS alert f/text
    ]
    t: text-list 400x300 "Select this line" "Then this one" "Now this" [
        alert value                 ; SAME AS alert t/text
    ]
    check yellow [alert "You clicked the yellow check box."]
    button "Quit" [alert "I don't want to stop yet!"]    
]

; List Widget:

y: read %.   c: 0   x: copy []
foreach i y [append/only x reduce [(c: c + 1) i (size? to-file i)]]
slider-pos: 0
view center-face layout [
    across space 0
    the-list: list 400x400 [
        across  space 0x0
        text 50 purple
        text 250 bold [editor read to-file face/text]
        text 100 red italic
        return box green 400x1
    ] supply [
        count: count + slider-pos
        if none? q: pick x count [face/text: none exit]
        face/text: pick q index
    ]
    scroller 16x400 [
        slider-pos: (length? x) * value
        show the-list
    ]
]

view layout [
    h3 "Just a few effects - fit, flip, emboss:"
    area 400x400 load http://rebol.com/view/bay.jpg effect [
        Fit Flip Emboss              ; you can fit images on most widgets
    ]
]

effects:  [
  invert  contrast 40  colorize 0.0.200  gradcol 1x1 0.0.255 255.0.0
  tint 100  luma -80  multiply 80.0.200  grayscale  emboss  flip 0x1 
  flip 1x0  rotate 90  reflect 1x1  blur  sharpen  aspect  tile tile-view
]
view layout [
    area 400x400 wrap rejoin [
        "And there are MANY more effects:" newline newline form effects
    ]
] 

view layout [area effect [gradient red blue]]  ; gradients are color fades
view layout [
    size 500x400
    backdrop effect [gradient 1x1 tan brown]
    box effect [gradient 123.23.56 254.0.12]
    box effect [gradient blue gold/2]
]

view layout [
    btn "Right/Left Click Me" [alert "left click"] [alert "right click"]
]

panels: layout [
    across
    btn "Fields"      [window/pane: pane1 show window]
    btn "Text List"   [window/pane: pane2 show window]
    return
    window: box 400x200
]
pane1: layout/tight [field 400 field 400 area 400]
pane2: layout/tight [text-list 400x200 data system/locale/days]
window/pane: pane1
view center-face panels

svv/vid-face/color: white
alert "New global background color is now white."

; The word "offset" refers to a widget's coordinate position.
; The word "style" builds a new widget with the specified style & actions:

view center-face layout [
    size 600x440 
    h3 "Press the left or right arrow key"
    key keycode [left]  [alert "You pressed the LEFT arrow key"]
    key keycode [right] [alert "You pressed the RIGHT arrow key"]
    btn #"a" "Click Me or Press the 'a' Key" [alert "clicked or pressed"]
]

; Here's a little program to show all key codes:

insert-event-func func [f e] [if e/type = 'key [print mold e/key] e]
view layout [text "Type keys to see their character/keycode"]

; How to refer to the main layout window:

view gui: layout [
    btn1: btn "Button 1"
    btn2: btn "Remove all widgets from window" [
        foreach item system/view/screen-face/pane/1/pane [
            remove find system/view/screen-face/pane/1/pane item
        ]
        show gui
    ]
]

; "Feel" and "Engage" together detect events:

view layout [
    text "Mouse me." feel [
        engage: func [face action event] [
            if action = 'up [print "You just released the mouse."]
        ]
    ]
]

print "Click anywhere in the window, then click the text."
view center-face layout [
    size 400x200
    box 400x200 feel [
        engage: func [f a e] [     ; f a e = face action event
            print rejoin ["Mouse " a " at " e/offset]
        ]
    ]
    origin 
    text "Click me" [print "Text clicked"] [print "Text right-clicked"]
    box blue [print "Box clicked"]
]

movestyle: [                     ; generic click and drag code
    engage: func [f a e] [
        if a = 'down [
            initial-position: e/offset
            remove find f/parent-face/pane f
            append f/parent-face/pane f
        ]
        if find [over away] a [
            f/offset: f/offset + (e/offset - initial-position)
        ]
        show f
    ]
]
view layout/size [
    style moveable-object box 20x20 feel movestyle
    at random 600x400 moveable-object (random 255.255.255)
    at random 600x400 moveable-object (random 255.255.255)
    at random 600x400 moveable-object (random 255.255.255)
    at random 600x400 moveable-object (random 255.255.255)
    at random 600x400 moveable-object (random 255.255.255)
    text "This text and all the boxes are movable" feel movestyle
] 600x440

; The following box code creates a repeating, multitasking loop in a GUI.
; The "within" function checks for graphic collisions:

view center-face layout [
    size 400x400
    btn1: btn red
    at 175x175 btn2: btn green
    box 0x0 rate 0 feel [engage: func [f a e] [if a = 'time [
        btn1/offset: btn1/offset + 5x5
        show btn1
        if within? btn1/offset btn2/offset 1x1 [alert "Collision" unview]
    ]]]
]

view center-face layout [                    ; follow all mouse movements
    size 600x440
    at 270x209 b: btn "Click Me - Aha!" feel [
        detect: func [f e] [
            if e/type = 'move [
                if (within? e/offset b/offset 59x22) [
                    b/offset: b/offset + ((random 50x50) - (random 50x50))
                    if not within? b/offset -59x-22 659x462 [
                        b/offset: 270x209
                    ]
                    show b
                ]
            ]
            e
        ]
    ]
]

; To trap other events (this example traps and responds to close events):

closer: insert-event-func [
    either event/type = 'close [
        really: request "Really close the program?"
        if really = true [remove-event-func :closer]
    ] [event]  ; always return other events
]
view center-face layout [
    text "Close me"
    size 600x400
]

insert-event-func [                    ; this example traps resize events
    either event/type = 'resize [
        fs: t1/parent-face/size
        t1/offset: fs / 2x2
        t2/offset: t1/offset - 50x25
        t3/offset: t1/offset - 25x50
        show gui  none
    ] [event]
]
svv/vid-face/color: white
view/options gui: layout [
    text "Centered in resized window:"
    across
    t1: text "50x50"
    t2: text "- 50x25"
    t3: text "- 25x50"
] [resize]

; Use "to-image" to create a SCREEN SHOT of any layout:

picture: to-image layout [
    page-to-read: field "http://rebol.com"
    btn "Display HTML"
]
save/png %layout.png picture     ; save the image to a file
browse %layout.png

flash "Just waiting..."  wait 3  alert "Done waiting!"  unview
inform layout [btn "Click Me" [flash "Just waiting..." wait 3 unview]]

; Embed files (images, sounds, etc.) in code:

alert "Select a picture from your hard drive:"
system/options/binary-base: 64
editor picture: compress to-string read/binary to-file request-file/only
view layout [image load (to-binary decompress picture)]

; This example embedded image was created with the script above:

logo-pic: load to-binary decompress #{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}
view layout [image logo-pic]

write/append %s ""                          ; A very compact GUI program
view center-face g: layout [
    h3 "Name:"   x: field   h3 "Info:"   z: area wrap   across
    btn "Save" [do-face d 1  save %s  repend f [x/text z/text]]
    btn "Load" [
        c: request-list" Select:" extract (f: load %s) 2
        if c = none [return]
        x/text: first find f c  z/text: select f x/text  show g
    ]
    btn "New" [x/text: copy ""  z/text: copy ""  show g  focus x]
    d: btn "Delete" [
        if true = request "Sure?" [
            remove/part (find (f: load %s) x/text) 2 save %s f alert "ok"
        ]
    ]
]

; Some examples of the "draw" dialect for creating graphics:

view layout [
    box 400x400 black effect [
        draw [
            pen red
            line 0x400 400x50
            pen white
            box 100x20 300x380
            fill-pen green
            circle 250x250 100
            pen blue
            fill-pen orange
            line-width 5
            spline closed 3 20x20 200x70 150x200
            polygon 20x20 200x70 150x200 50x300
        ]
    ]
]

view layout [
    box 400x220 effect [
        draw [
            fill-pen 200.100.90
            polygon 20x40 200x20 380x40 200x80
            fill-pen 200.130.110
            polygon 20x40 200x80 200x200 20x100
            fill-pen 100.80.50
            polygon 200x80 380x40 380x100 200x200
        ]
        gradmul 180.180.210 60.60.90
    ]
]
view layout [
    h3 "Draw On Me:"
    scrn: box black 400x400 feel [
        engage: func [face action event] [
            if find [down over] action [
                append scrn/effect/draw event/offset
                show scrn
            ]
            if action = 'up [append scrn/effect/draw 'line]
        ]
    ] effect [draw [line]]
]

pos: 300x300
view layout [
    scrn: box pos black effect [
        draw [image logo.gif 0x0 300x0 300x300 0x300]
    ]
    btn "Animate" [
        for point 1 450 4 [
            scrn/effect/draw: copy reduce [
                'image logo.gif 
                (pos - 300x300)
                (1x1 + (as-pair 300 point))
                (pos - (as-pair 1 point))
                (pos - 300x0)
            ]
            show scrn
        ]
        scrn/effect/draw: copy [
            image logo.gif 0x0 300x0 300x300 0x300
        ]
        show scrn
    ]
]

See http://rebol.com/docs/easy-vid.html and http://rebol.com/docs/view-guide.html for some additional information and examples demonstrating basic GUI techniques.

4.4 A Telling Comparison

To provide a quick idea of how much easier REBOL is than other languages, here's a short example. The following code to create a basic program window with REBOL was presented earlier:

view layout [size 400x300]

It works on every type of computer, in exactly the same way.

Code for the same simple example is presented below in the C++ language. It does the exact same thing as the REBOL one-liner above, except it only works on Microsoft Windows machines. If you want to do the same thing with a Macintosh computer, you need to memorize a completely different page of C++ code. The same is true for Linux or any other operating system. You have to learn enormous chunks of code to do very simple things, and those chunks of code are different for every type of computer. Furthermore, you typically need to spend a semester's worth of time learning very basic things about code syntax and fundamentals about how a computer 'thinks' before you even begin to tackle useful basics like the code below:

#include <windows.h>

/*  Declare Windows procedure  */
LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);

/*  Make the class name into a global variable  */
char szClassName[ ] = "C_Example";

int WINAPI
WinMain (HINSTANCE hThisInstance,
         HINSTANCE hPrevInstance,
         LPSTR lpszArgument,
         int nFunsterStil)

{
    HWND hwnd;               
    /* This is the handle for our window */
    MSG messages;            
    /* Here messages to the application are saved */
    WNDCLASSEX wincl;        
    /* Data structure for the windowclass */

    /* The Window structure */
    wincl.hInstance = hThisInstance;
    wincl.lpszClassName = szClassName;
    wincl.lpfnWndProc = WindowProcedure;      
    /* This function is called by windows */
    wincl.style = CS_DBLCLKS;                 
    /* Catch double-clicks */
    wincl.cbSize = sizeof (WNDCLASSEX);

    /* Use default icon and mouse-pointer */
    wincl.hIcon = LoadIcon (NULL, IDI_APPLICATION);
    wincl.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
    wincl.hCursor = LoadCursor (NULL, IDC_ARROW);
    wincl.lpszMenuName = NULL;                 
    /* No menu */
    wincl.cbClsExtra = 0;                      
    /* No extra bytes after the window class */
    wincl.cbWndExtra = 0;                      
    /* structure or the window instance */
    /* Use Windows's default color as window background */
    wincl.hbrBackground = (HBRUSH) COLOR_BACKGROUND;

    /* Register window class. If it fails quit the program */
    if (!RegisterClassEx (&wincl))
        return 0;

    /* The class is registered, let's create the program*/
    hwnd = CreateWindowEx (
           0,                   
            /* Extended possibilites for variation */
           szClassName,         
            /* Classname */
           "C_Example",       
            /* Title Text */
           WS_OVERLAPPEDWINDOW, 
            /* default window */
           CW_USEDEFAULT,       
            /* Windows decides the position */
           CW_USEDEFAULT,       
            /* where the window ends up on the screen */
           400,                 
            /* The programs width */
           300,                 
            /* and height in pixels */
           HWND_DESKTOP,        
            /* The window is a child-window to desktop */
           NULL,                
            /* No menu */
           hThisInstance,       
            /* Program Instance handler */
           NULL                
            /* No Window Creation data */
           );

    /* Make the window visible on the screen */
    ShowWindow (hwnd, nFunsterStil);

    /* Run the message loop. 
        It will run until GetMessage() returns 0 */
    while (GetMessage (&messages, NULL, 0, 0))
    {
        /* Translate virtual-key messages 
            into character messages */
        TranslateMessage(&messages);
        /* Send message to WindowProcedure */
        DispatchMessage(&messages);
    }

    /* The program return-value is 0 - 
        The value that PostQuitMessage() gave */
    return messages.wParam;
}

/*  This function is called by the Windows 
        function DispatchMessage()  */

LRESULT CALLBACK
WindowProcedure (HWND hwnd, UINT message, 
    WPARAM wParam, LPARAM lParam)
{
    switch (message)                  
    /* handle the messages */
    {
        case WM_DESTROY:
            PostQuitMessage (0);       
                /* send a WM_QUIT to the message queue */
            break;
        default:                      
            /* for messages that we don't deal with */
            return DefWindowProc (hwnd, message, 
                wParam, lParam);
    }

    return 0;
}

Yuck. Back to REBOL...

5. Quick Review and Clarification

The list below summarizes some key characteristics of the REBOL language. Knowing how to put these elements to use constitutes a fundamental understanding of how REBOL works:

  1. To start off, REBOL has hundreds of built-in function words that perform common tasks. As in other languages, function words are typically followed by passed data parameters. Unlike other languages, passed parameters are placed immediately after the function word and are not necessarily enclosed in parentheses. To accomplish a desired goal, functions are arranged in succession, one after another. The value(s) returned by one function are often used as the argument(s) input to another function. Line terminators are not required at any point, and all expressions are evaluated in left to right order, then vertically down through the code. Empty white space (spaces, tabs, newlines, etc.) can be inserted as desired to make code more readable. Text after a semicolon and before a new line is treated as a comment. You can complete significant work by simply knowing the predefined functions in the language, and organizing them into a useful order.
  2. REBOL contains a rich set of conditional structures, which can be used to manage program flow and data processing activities. If, either, and other typical structures are supported.
  3. Because many common types of data values are automatically recognized and handled natively by REBOL, calculating, looping, and making conditional decisions based upon data content is straightforward and natural to perform, without any external modules or toolkits. Numbers, text strings, money values, times, tuples, URLs, binary representations of images, sounds, etc. are all automatically handled. REBOL can increment, compare, and perform proper computations on most common types of data (i.e., the interpreter automatically knows that 5:32am + 00:35:15 = 6:07:15am, and it can automatically apply visual effects to raw binary image data, etc.). Network resources and Internet protocols (http documents, ftp directories, email accounts, dns services, etc.) can also be accessed natively, just as easily as local files. Data of any type can be written to and read from virtually any connected device or resource (i.e., "write %file.txt data" works just as easily as "write ftp://user:pass@website.com data", using the same common syntax). The percent symbol ("%") and the syntax "%(/drive)/path/path/.../file.ext" are used cross-platform to refer to local file values on any operating system.
  4. Any data or code can be assigned a word label. The colon character (":") is used to assign word labels to constants, variable values, evaluated expressions, and data/action blocks of any type. Once assigned, variable words can be used to represent all of the data contained in the given expression, block, etc. Just put a colon at the end of a word, and thereafter it represents all the following data.
  5. Multiple pieces of data are stored in "blocks", which are delineated by starting and ending brackets ("[]"). Blocks can contain data of any type: groups of text strings, arrays of binary data, other enclosed blocks, etc. Data items contained in blocks are separated by white space. Blocks can be automatically treated as lists of data, called "series", and manipulated using built-in functions that enable searching, sorting, ordering, and otherwise organizing the blocked data. Blocks are used to delineate most of the syntactic structures in REBOL (i.e., actions resulting from conditional evaluations, GUI widget layouts, etc.).
  6. "Foreach" function can be used to process lists and tables of data. Rows and columns if data in tables can be processed using the format: "foreach [col1 col2 col3...] table-block [do something to each row pof values]". Data can be saved to CSV files by rejoining molded (quoted) text and delimiters. CSV files can be read using the "read/lines" and "parse" functions. Sorting data by column with the sort/compare function requires that rows be saved in nested blocks, rather than as "flat" sequential lists of items. Data stored as (quoted) text string values is sorted alphabetically. Data stored or converted to specific data type values is sorted appropriately for the type.
  7. The syntax "view layout [block]" is used to create basic GUI layouts. You can add widgets to the layout simply by placing widget identifier words inside the block: "button", "field", "text-list", etc. Color, position, spacing, and other facet words can be added after each widget identifier. Action blocks added immediately after any widget will perform the enclosed functions whenever the widget is activated (i.e., when the widget is clicked with a mouse, when the enter key pressed, etc.). Path refinements can be used to refer to items in the GUI layout (i.e., "face/offset" refers to the position of the selected widget face, "face/text" to it's text, etc.). Those simple guidelines can be used to create useful GUIs for data input and output, in a way that's native (doesn't require any external toolkits) and much easier than any other language.

6. SOME COMPLETE GUI APPLICATION EXAMPLES

The examples in this section were presented at the very beginning of the tutorial as demonstrations. At this point in the tutorial, you should now be able to understand every bit of code in each program! Every example in this section is documented with detailed line-by-line explanations of what each function, variable, and language construct does. Run every example in the REBOL interpreter, and read every line of code, along with all the comments. Really pay attention to the material in this section - it's one of the most formative in the entire text. Not only are the applications useful as a basis for more personalized production pieces of software, the logic and code patterns demonstrated here will form a strong fundamental understanding about how to create other imagined pieces of software.

6.1 Generic Text Field Saver

Little programs like this form the initial basis for all types of simple data entry app. The entered data is stored in CSV file format, so it can be easily opened by a spreadsheet or other program:

REBOL [title: "Text Field Saver"]

; The words "view layout" create a GUI window:

view layout [

    ; Create 3 text fields widgets labeled f1, f2, and f3:

    f1: field
    f2: field
    f3: field

    ; Create a button widget:
    btn "Save" [

        ; When the button is clicked, write to the file fields.txt some
        ; rejoined text.  The /append refinement of the write function
        ; ensures that data is ADDED to the end of the existing text file,
        ; instead of erasing the file and writing totally new data to it.
        ; If the fields.csv file doesn't exist, it's created:

        write/append %fields.csv rejoin [

            ; The "mold" function surrounds text with quotes.
            ; So the concatenated text written to the fields.txt file
            ; includes the quoted text from each field widget above, 
            ; each separated by a comma and a quote, and completed with
            ; a carriage return:

            mold f1/text ", " mold f2/text ", " mold f3/text newline

        ]

        ; Alert the user when the data has been saved:

        alert "Saved"

    ]
]

Here's the whole program without comments. It's tiny:

REBOL [title: "Text Field Saver"]
view layout [
    f1: field
    f2: field
    f3: field
    btn "Save" [
        write/append %fields.txt rejoin [
            mold f1/text ", " mold f2/text ", " mold f3/text newline
        ]
        alert "Saved"
    ]
]

6.2 Calculator

This calculator is as basic as could be, but adding advanced math functions and other useful capabilities is easy. Imagine adding industry specific operations such as amortization calculations. The potential to add genuinely useful unique features is limitless (see the next example below, which performs currency conversion operations that draw from current live rates on the Internet, for example). At this point, try to understand the fundamental layout and operation of the GUI widgets:

REBOL [title: "Calculator"]

; Create a GUI Window:

view layout [

    ; Set the layout properties so that widgets are placed immediately
    ; next to one another, starting at the top left corner of the screen:

    origin 0  space 0x0  across

    ; Here's a text field, labeled "f".  It's size is 200 pixels across
    ; and 40 pixels down.  The font size of text in the field is set to
    ; 20.  After this field widget, the "return" word is used to jump
    ; to the beginning of a new line:

    f: field 200x40 font-size 20  return

    ; The "style" word below is used to create a new widget called "btn",
    ; which is a button, sized 50 pixels by 50 pixels.  When clicked, the
    ; button appends the text on it's face to the text field widget above,
    ; labeled "f", then the display is updated using the "show" function:

    style btn btn 50x50 [append f/text face/text  show f]

    ; Below the field widget are 4 lines of buttons, displaying either
    ; numbers or operators on their face.  Each of these buttons performs
    ; the actions defined above in the "style" definition (appends its
    ; face text to the field widget display):

    btn "1"  btn "2"  btn "3"  btn " + "  return
    btn "4"  btn "5"  btn "6"  btn " - "  return
    btn "7"  btn "8"  btn "9"  btn " * "  return
    btn "0"  btn "."  btn " / "   btn "=" [

        ; When the "=" button is pressed, the "f" field text is set to the
        ; result of the expression displayed in the "f" field text (the 
        ; evaluation is performed using the "do" function), and the
        ; display is updated with the "show" function.  Remember, the
        ; "form" function is used to convert the result to a text string
        ; value, which is the only type of data that text field widgets
        ; display.  The "attempt" function is used to keep the program
        ; from crashing if the user tries to enter an illegal expression,
        ; such as division by zero or incomplete expressions (i.e., 1 + ):

        attempt [f/text: form do f/text  show f]

    ]
]

Here's the whole program, without comments:

REBOL [title: "Calculator"]
view layout [
    origin 0  space 0x0  across
    f: field 200x40 font-size 20 return
    style btn btn 50x50 [append f/text face/text  show f]
    btn "1"  btn "2"  btn "3"  btn " + "  return
    btn "4"  btn "5"  btn "6"  btn " - "  return
    btn "7"  btn "8"  btn "9"  btn " * "  return
    btn "0"  btn "."  btn " / "   btn "=" [
        attempt [f/text: form do f/text  show f]
    ]
]

The following example downloads and parses the current (live) US Dollar exchange rates from http://x-rates.com and allows the user to select from a list of currencies to convert to, then performs and displays the conversion from USD to the selected currency. This example will likely be a bit too advanced to understand completely at this point in the tutorial, but it's good to run it in the REBOL interpreter and browse through the code to recognize functions such as "read", "find", "parse", "attempt", etc., to which you've already been introduced. See if you can get a general concept of what the code is doing:

REBOL [title: "Currency Rate Conversion Calculator"]
view center-face layout [
    origin 0  space 0x0  across
    f: field 200x40 font-size 20
    return
    style btn btn 50x50 [append f/text face/text  show f]
    btn "1"  btn "2"  btn "3"  btn " + "  return
    btn "4"  btn "5"  btn "6"  btn " - "  return
    btn "7"  btn "8"  btn "9"  btn " * "  return
    btn "0"  btn "."  btn " / "   btn "=" [
        attempt [f/text: form do f/text  show f]
    ] return
    btn 200x35 "Convert" [
        x: copy []
        html: read http://www.x-rates.com/table/?from=USD&amount=1.00
        html: find html "src='/themes/bootstrap/images/xrates_sm_tm.png'"
        parse html [
            any [
                thru {from=USD} copy link to {</a>} (append x link)
            ] to end 
        ]
        rates: copy []
        foreach rate x [
            parse rate [thru {to=} copy c to {'>}]
            parse rate [thru {'>} copy v to end]
            if not error? try [to-integer v] [append rates reduce [c v]]
        ]  
        currency: request-list "Select Currency:" extract rates 2
        rate: to-decimal select rates currency
        attempt [alert rejoin [currency ": " (rate * to-decimal f/text)]]
    ]
]

6.3 File Editor

Next is an example of a text editor that allows you to read, edit, and save any text file. Here's the GUI layout code. It consists of a "h1" header text widget displaying the text "Text Editor:", a 600 pixel wide field widget labeled "f" containing the text "filename.txt", a 600x350 pixel area widget labeled "a", and two buttons aligned across the screen (next to each other):

REBOL []
view layout [
    h1 "Text Editor:"
    f: field 600 "filename.txt"
    a: area 600x350 
    across 
    btn "Load" []
    btn "Save" []
]

And here's the full code that makes it run:

REBOL []
view layout [
    h1 "Text Editor:"
    f: field 600 "filename.txt"
    a: area 600x350 
    across 
    btn "Load" [

        ; When the load button is pressed, request a file name from the
        ; user, and display it in the "f" field.  Be sure to update the
        ; display using the "show" function:

        f/text: request-file
        show f

        ; In order to load the file, the text version of file name
        ; displayed in the field must be converted from text to a file
        ; value:

        filename: to-file f/text

        ; Set text in the area widget to the data read from file location,
        ; and update the display:

        a/text: read filename 
        show a

    ]
    btn "Save" [

        ; When the save button is clicked, request a file name from the
        ; user.  The default file name shown in the requestor is the text
        ; currently displayed in the "f" field: 

        filename: to-file request-file/save/file f/text

        ; Write to the selected file name, the text contained in the "a"
        ; area widget:

        write filename a/text

        ; Alert the user when the file is saved:

        alert "Saved"

    ]
]

Here's the whole program without comments:

REBOL [title: "Text Editor"]
view layout [
    h1 "Text Editor:"
    f: field 600 "filename.txt"
    a: area 600x350 
    across 
    btn "Load" [
        f/text: request-file
        show f
        filename: to-file f/text
        a/text: read filename 
        show a
    ]
    btn "Save" [
        filename: to-file request-file/save/file f/text
        write filename a/text
        alert "Saved"
    ]
]

6.4 Web Page Editor

REBOL can read and write to FTP (web site) servers just as easily as it can to local files. All you need to know is an account username/password, folder location on the server (often "public_html"), and a file name to edit. Here's a variation of the program above repurposed as a web page editor:

REBOL [title: "Web Page Editor"]
view layout [
    h1 "Web Page Editor:"
    f: field 600 "ftp://user:pass@site.com/public_html/file.txt"
    a: area 600x350 
    across 
    btn "Load" [

        ; Be sure to convert the file name text in "a" area widget to a
        ; URL data value.  Set text in the area widget to the data read
        ; from the URL location:

        a/text: read to-url f/text 
        show a

    ]
    btn "Save" [

        ; Covert the text in "a" area widget to a URL value and write the
        ; data in the "a" area widget to the URL:

        write (to-url f/text) a/text
        alert "Saved"

    ]
]

Here's the whole program without comments:

REBOL [title: "Web Page Editor"]
view layout [
    h1 "Web Page Editor:"
    f: field 600 "ftp://user:pass@site.com/public_html/page.html"
    a: area 600x350 
    across 
    btn "Load" [
        a/text: read to-url f/text 
        show a
    ]
    btn "Save" [
        write (to-url f/text) a/text
        alert "Saved"
    ]
]

6.5 Inventory List Creator

This is another simple GUI field example. It's very similar to the first example, but improved a bit with text labels for each field and repurposed to satisfy a very concise specialized task. It creates an inventory list using a simple GUI form. The file created is a list that can be used as needed to re-order required items, to calculate inventory and sales tax due, etc. Here's the GUI layout code:

REBOL [title: "Inventory"]
view layout [
    text "SKU:"
    f1: field
    text "Cost:"
    f2: field "1.00"
    text "Quantity:"
    f3: field
    across
    btn "Save" []
    btn "View Data" []
]

And here's the code that makes the entire inventory program run:

REBOL [title: "Inventory"]
view layout [
    text "SKU:"
    f1: field
    text "Cost:"
    f2: field "1.00"
    text "Quantity:"
    f3: field
    across
    btn "Save" [
        write/append %inventory.txt rejoin [
            mold f1/text " " mold f2/text " " mold f3/text newline
        ]
        alert "Saved"
    ]

    ; A button is added to allow viewing/editing of the saved data, using
    ; REBOL text editor function:

    btn "View Data" [editor %inventory.txt]
]

Here's whole program without comments:

REBOL [title: "Inventory"]
view layout [
    text "SKU:"
    f1: field
    text "Cost:"
    f2: field "1.00"
    text "Quantity:"
    f3: field
    across
    btn "Save" [
        write/append %inventory.txt rejoin [
            mold f1/text " " mold f2/text " " mold f3/text newline
        ]
        alert "Saved"
    ]
    btn "View Data" [editor %inventory.txt]
]

6.6 Inventory Sorter and Viewer

The inventory program creates lists of data that look like this (saved in the file "inventory.txt"):

"932984729812" "1.00" "14"
"392328389483" "2.59" "93"
"602374822852" "4.92" "3"

This little program allows users to view the inventory data, sorted by a chosen column. You've already seen most of the important code patterns in this example, during the discussion about sorting columns of values in a table:

REBOL [title: "Sort Inventory"]

; Load the data block from the inventory.txt file and label it
: "inventory":

inventory: load %inventory.txt

; Create a new empty block named "blocked":

blocked: copy []

; Convert the "flat" data in the "inventory" block to "blocked" format
; (with rows delineated as separate blocks).  Remember, as shown earlier,
; the "append/only" function refinement makes this easy to do.  Just run
; a "foreach" function on every 3 items in the "inventory" block, and
; add each group of three items as a new block within the "blocked" block.
; Notice that during the process, the "cost" and "qty" are converted from
; strings to money and number values:

foreach [sku cost qty] inventory [
    append/only blocked reduce [
        sku 
        to-money cost
        to-integer qty
    ]
]

; Use the "request-list" function to allow the user to select a column to
; sort by.  Assign the response to the variable "field-name":

field-name: request-list "Choose Field To Sort By:" [
    "sku" "cost" "qty"
]

; The "select" function chooses the next value in a list, selected by the
; user.  In this case if the field-name variable equals "sku", the "field"
; variable is set to 1.  If field-name="cost", the "field" variable is set
; to 2.  If field-name="qty", then "field" is set to 3: 

field: select ["sku" 1 "cost" 2 "qty" 3] field-name

; Use the "request-list" function to allow the user to select an order to
; sort by.  Assign the response to the label "order":

order: request-list "Ascending or Descending:" ["ascending" "descending"]

; Sort by the appropriate "field" column, ascending or descending, 
; depending on the value of the "order" variable:

either order = "ascending" [
    sort/compare blocked func [a b] [(at a field) < (at b field)]
][
    sort/compare blocked func [a b] [(at a field) > (at b field)]
]

; Use the foreach function to loop through the sorted "blocked" block of
; data.  Print the 3 items in each block within the "blocked" block:

foreach item blocked [
    print rejoin [
        "SKU:  " item/1           ; The 1st item in each block is the SKU.
        "  COST: " item/2         ; 2nd item is the cost.
        "  QTY: " item/3          ; 3rd item is the quantity.
        newline                   ; print a carriage return at the end
    ]
]
halt

Here's the whole program without comments:

REBOL [title: "Sort Inventory"]
inventory: load %inventory.txt
blocked: copy []
foreach [sku cost qty] inventory [
    append/only blocked reduce [
        sku 
        to-money cost
        to-integer qty
    ]
]
field-name: request-list "Choose Field To Sort By:" [
    "sku" "cost" "qty"
]
field: select ["sku" 1 "cost" 2 "qty" 3] field-name
order: request-list "Ascending or Descending:" ["ascending" "descending"]
either order = "ascending" [
    sort/compare blocked func [a b] [(at a field) < (at b field)]
][
    sort/compare blocked func [a b] [(at a field) > (at b field)]
]
foreach item blocked [
    print rejoin [
        "SKU:  " item/1 
        "  COST: " item/2 
        "  QTY: " item/3 
        newline
    ]
]
halt

6.7 Contacts Viewer

Here's a contact database app that displays user information in a tabular display:

REBOL [title: "Contacts"]

; First create a block of user data.  15 values - 5 rows, 3 columns:

users: [
    "John Smith" "123 Tomline Lane Forest Hills, NJ" "555-1234"
    "Paul Thompson" "234 Georgetown Pl. Peanut Grove, AL" "555-2345"
    "Jim Persee" "345 Pickles Pike Orange Grove, FL" "555-3456"
    "George Jones" "456 Topforge Court Mountain Creek, CO" ""
    "Tim Paulson" "" "555-5678"
]

; Next, define a GUI layout block.  White background, widgets positioned
; next to each other horizontally, a new "header" text widget style which
; is 200 pixels wide, and 3 of those widgets containing appropriate header
; labels for each column of data, followed by a new GUI line:

gui: [
    backdrop white
    across
    style header text 200
    header "Name:" header "Address:" header "Phone:" return
]

; Use the foreach function to loop through each row in the user block:

foreach [name address phone] users [

    ; For each row in the user block, add the following code to the GUI
    ; layout block:

    append gui compose [

        ; Add a new field widget containing each row's name, address, and
        ; phone values.  The "compose" function above converts the
        ; parenthesized words below to evaluated values (the text data
        ; in each row, instead of the text "name", "address", "phone"):

        field (name) field (address) field (phone) return

    ]
]

; Show the constructed GUI block:

view layout gui

Here's the whole program without comments:

REBOL [title: "Contacts"]
users: [
    "John Smith" "123 Tomline Lane Forest Hills, NJ" "555-1234"
    "Paul Thompson" "234 Georgetown Pl. Peanut Grove, AL" "555-2345"
    "Jim Persee" "345 Pickles Pike Orange Grove, FL" "555-3456"
    "George Jones" "456 Topforge Court Mountain Creek, CO" ""
    "Tim Paulson" "" "555-5678"
]
gui: [
    backdrop white
    across
    style header text black 200
    header "Name:" header "Address:" header "Phone:" return
]
foreach [name address phone] users [
    append gui compose [
        field (name) field (address) field (phone) return
    ]
]
view layout gui

This app combines some the techniques used in the previous two examples, to create a prettier sorted inventory display:

REBOL [title: "Sort Inventory"]

; First, load some data created by the inventory app.  Assign the loaded
; block to the variable label "inventory":

inventory: load %inventory.txt

; Create a new empty block:

blocked: copy []

; Create a block of blocks, so that the data can be sorted by columns,
; with column data converted from text to money and integer values.
; The "reduce" function works just like "compose", but does not require
; parentheses:

foreach [sku cost qty] inventory [
    append/only blocked reduce [
        sku 
        to-money cost
        to-integer qty
    ]
]

; Use the "request-list" requestor to get a sort column from the user.
; Assign the user's response to the variable label "field-name":

field-name: request-list "Choose Field To Sort By:" [
    "sku" "cost" "qty"
]

; Used the "select" function to assign a number value to the column
; chosen above.  Assign that number to variable label "field":

field: select ["sku" 1 "cost" 2 "qty" 3] field-name

; Use the "request-list" requestor to get a sort order from the user.
; Assign the user's response to the variable label "order":

order: request-list "Ascending or Descending:" ["ascending" "descending"]

; If the chosen sort order is "ascending", sort the block of blocks in
; ascending order, based on the chosen "field" column.  Otherwise, sort
; it in descending order:

either order = "ascending" [
    sort/compare blocked func [a b] [(at a field) < (at b field)]
][
    sort/compare blocked func [a b] [(at a field) > (at b field)]
]

; Create a GUI block with some 200 pixel wide text headers:

gui: [
    backdrop white
    across
    style header text black 200
    header "SKU:" header "Cost:" header "Qty:" return
]

; For each row in the block of blocks, append 3 fields containing the
; name, address, and phone text, to the GUI layout:

foreach row blocked [
    append gui compose [
        field (form row/1) field (form row/2) field (form row/3) return
    ]
]

; View the GUI layout:

view center-face layout gui

Here's the whole program without comments:

REBOL [title: "Sort Inventory"]
inventory: load %inventory.txt
blocked: copy []
foreach [sku cost qty] inventory [
    append/only blocked reduce [
        sku 
        to-money cost
        to-integer qty
    ]
]
field-name: request-list "Choose Field To Sort By:" [
    "sku" "cost" "qty"
]
field: select ["sku" 1 "cost" 2 "qty" 3] field-name
order: request-list "Ascending or Descending:" ["ascending" "descending"]
either order = "ascending" [
    sort/compare blocked func [a b] [(at a field) < (at b field)]
][
    sort/compare blocked func [a b] [(at a field) > (at b field)]
]
gui: [
    backdrop white
    across
    style header text black 200
    header "SKU:" header "Cost:" header "Qty:" return
]
foreach row blocked [
    append gui compose [
        field (form row/1) field (form row/2) field (form row/3) return
    ]
]
view center-face layout gui

6.8 Minimal Retail Cash Register and Sales Report System

The example below is a trivial POS ("Point of Sale", or retail cash register) program:

REBOL [title: "Minimal Cash Register"]
view gui: layout [

    ; Create a new widget style named "fld".  It's just a text field, 
    ; 80 pixels wide:

    style fld field 80

    ; Place consecutive widgets next to each other:

    across

    ; Here are 3 text labels and 3 text entry fields to allow users to
    ; enter a cashier name, item name, and price.  The text entry fields
    ; are labeled appropriately:

    text "Cashier:"   cashier: fld 
    text "Item:"      item: fld 
    text "Price:"     price: fld [

        ; When the user enters a price, perform the following operations:
        ; First, check to make sure the price entered can be converted to
        ; a money value.  If not, alert the user with an error message and
        ; exit the action block:

        if error? try [to-money price/text] [alert "Price error" return]

        ; Otherwise, add the quoted item text, and the price to the area
        ; widget (separated by a few spaces):

        append a/text reduce [mold item/text "    " price/text newline]

        ; Then erase the text in the item and price entry fields:

        item/text: copy "" price/text: copy ""

        ; Now, compute a subtoal of all the entered items.  Update the
        ; subtotal, tax, and total amount fields with the appropriate
        ; computed values:

        sum: 0
        foreach [item price] load a/text [sum: sum + to-money price]
        subtotal/text: form sum
        tax/text: form sum * .06
        total/text: form sum * 1.06 

        ; Put the cursor back in the "item" field, and update the display:

        focus item
        show gui

    ]

    ; On a new row, put an area widget, 600 pixels across and 300 tall,
    ; labeled "a":

    return
    a: area 600x300

    ; On a new line, 3 more text and field widgets, labeled appropriately,
    : and a button with the text "Save":

    return
    text "Subtotal:"   subtotal: fld 
    text "Tax:"        tax: fld 
    text "Total:"      total: fld
    btn "Save" [

        ; When the button is pressed, do the following:
        ; first create a quoted block of items in the area widget.
        ; Replace all the newline characters with a space, so that all
        ; the data is on one line.  Label the whole chunk of data "items":

        items: replace/all (mold load a/text) newline " "

        ; Append the "items" data, the cashier name, and the date to the
        ; file "sales.txt" (all separated by carriage returns):

        write/append %sales.txt rejoin [
            items newline cashier/text newline now/date newline
        ]

        ; Erase all the text in every field widget, erase the text in the
        ; the area widget, and update the display:

        clear-fields gui
        a/text: copy ""             
        show gui             

    ]
]

The code below reports the total sum of cash register sales for the current day:

REBOL [title: "Daily Total"]

; Read in each line of the "sales.txt" block, and label it "sales":

sales: read/lines %sales.txt

; Label a variable to hold a computed sum, and set it initially to $0:

sum: $0

; Use a foreach loop to go through every 3 items in the sales data
; (remember each group of items, cashier, and date were separated by a 
; newline in the code above):

foreach [items cashier date] sales [

    ; If the today's date is foun in any saved date entry:

    if now/date = to-date date [

       ; Use a foreach loop to go through the values in the "items" data:

        foreach [item price] load items [

            ; Add the price value to the computed sum:

            sum: sum + to-money price

        ]
    ]
]

; Alert the user with the computed sum:

alert rejoin ["Total sales today: " sum]

The report below shows the total of all items sold on any chosen day, by any chosen cashier:

REBOL [title: "Cashier Report"]

; Start by requesting a selected date and the name of a cashier:

report-date: request-date
report-cashier: request-text/title "Cashier:" 

; Read in the lines of the "sales.txt" file:

sales: read/lines %sales.txt

; Prepare to compute a sum value:

sum: $0

; Use a foreach loop to go through each entry in the sales data:

foreach [items cashier date] sales [

    ; Perform 2 conditional evaluations to check for any entries in which
    ; the selected cashier name and date match:

    if ((report-cashier = cashier) and (report-date = to-date date)) [

        ; For any entry that matches, add to the sum:

        foreach [item price] load items [
            sum: sum + to-money price
        ]

    ]
]

; Alert the user with a concatenated message:

alert rejoin ["Total for " report-cashier " on " report-date ": " sum]

Here are all 3 programs, without comments:

REBOL [title: "Minimal Cash Register"]
view gui: layout [
    style fld field 80
    across
    text "Cashier:"   cashier: fld 
    text "Item:"      item: fld 
    text "Price:"     price: fld [
        if error? try [to-money price/text] [alert "Price error" return]
        append a/text reduce [mold item/text "    " price/text newline]
        item/text: copy "" price/text: copy ""
        sum: 0
        foreach [item price] load a/text [sum: sum + to-money price]
        subtotal/text: form sum
        tax/text: form sum * .06
        total/text: form sum * 1.06 
        focus item
        show gui
    ]
    return
    a: area 600x300
    return
    text "Subtotal:"   subtotal: fld 
    text "Tax:"        tax: fld 
    text "Total:"      total: fld
    btn "Save" [
        items: replace/all (mold load a/text) newline " "
        write/append %sales.txt rejoin [
            items newline cashier/text newline now/date newline
        ]
        clear-fields gui
        a/text: copy ""             
        show gui             
    ]
]

REBOL [title: "Daily Total"]
sales: read/lines %sales.txt
sum: $0
foreach [items cashier date] sales [
    if now/date = to-date date [
        foreach [item price] load items [
            sum: sum + to-money price
        ]
    ]
]
alert rejoin ["Total sales today: " sum]

REBOL [title: "Cashier Report"]
report-date: request-date
report-cashier: request-text/title "Cashier:" 
sales: read/lines %sales.txt
sum: $0
foreach [items cashier date] sales [
    if ((report-cashier = cashier) and (report-date = to-date date)) [
        foreach [item price] load items [
            sum: sum + to-money price
        ]
    ]
]
alert rejoin ["Total for " report-cashier " on " report-date ": " sum]

6.9 Email

This example is a complete graphical email client that can be used to read and send messages. It has a button feature which allows the user to enter all necessary email account settings:

REBOL [Title: "Little Email Client"] 

; The line below creates the program's GUI window:

view layout [

    ; This line adds a text label to the GUI:

    h1 "Send Email:"

    ; This line adds a button to the GUI:

    btn "Server settings" [

        ; When the button is clicked, the following lines are run.
        ; These lines set all the email user account information
        ; required to send and receive email.  The settings are gotten
        ; from the user with the "request-text" function, and assigned
        ; to their appropriate locations in the REBOL system:

        system/schemes/default/host: request-text/title "SMTP Server:"
        system/schemes/pop/host:     request-text/title "POP Server:"
        system/schemes/default/user: request-text/title "SMTP User Name:"
        system/schemes/default/pass: request-text/title "SMTP Password:"
        system/user/email: to-email request-text/title "Your Email Addr:"

    ]

    ; This line creates a text entry field, containing the default text
    ; "recipient@website.com".  The variable word "address" is assigned to
    ; this widget:

    address: field "recipient@website.com"

    ; Heres another text entry field, for the email subject line:

    subject: field "Subject" 

    ; This line creates a larger, multi-line text entry area for the body
    ; text of the email:

    body: area "Body"

    ; Here's a button displaying the word "send".  The functions inside
    ; its action block are executed whenever the button is clicked:

    btn "Send" [

        ; This line does most of the work.  It uses the REBOL "send" 
        ; function to send the email.  The send function, with its
        ; "/subject" refinement accepts three parameters.  It's passed the
        ; current text contained in each field labeled above (referred to
        ; as "address/text" "body/text" and "subject/text").  The
        ; "to-email" function ensures that the address text is treated as
        ; an email data value:

        send/subject (to-email address/text) body/text subject/text

        ; This line alerts the user when the previous line is complete:

        alert "Message Sent."

    ]

    ; Here's another text label:

    h1 "Read Email:"

    ; Here's another text entry field.  The user's email account info is
    ; entered here.

    mailbox: field "pop://user:pass@site.com"

    ; This last button has an action block that reads messages from a
    ; specified mailbox.  It only takes one line of code:

    btn "Read" [

        ; The "to-url" function ensures that the text in the mailbox field
        ; is treated as a URL.  The contents of the mailbox are read and
        ; displayed using REBOL's built-in text editor:

        editor read to-url mailbox/text

    ]
]

Here's the whole program without comments:

view layout[
    h1 "Send:"
    btn "Server settings" [
        system/schemes/default/host: request-text/title "SMTP Server:"
        system/schemes/pop/host:     request-text/title "POP Server:"
        system/schemes/default/user: request-text/title "SMTP User Name:"
        system/schemes/default/pass: request-text/title "SMTP Password:"
        system/user/email: to-email request-text/title "Your Email Addr:"
    ]
    a: field "user@website.com"
    s: field "Subject" 
    b: area
    btn "Send"[
        send/subject to-email a/text b/text s/text
        alert "Sent"
    ]
    h1 "Read:" 
    f: field "pop://user:pass@site.com"
    btn "Read" [editor read to-url f/text]
]

6.10 Scheduler

Here's the GUI code for a scheduling app that allows users to create events on any day. Later, the user can click any day on the calendar to see the scheduled events:

view center-face gui: layout [
    btn "Date" []
    date: field
    text "Event Title:"
    event: field
    text "Time:"
    time: field
    text "Notes:"
    notes: field
    btn "Add Appoinment" []
    a: area
    btn "View Schedule" []
]

Here's the final code that makes the whole scheduling app run. This entire program is really nothing more complex than the field saver, inventory, cash register, and other GUI examples you've seen so far. There are just a few more widgets, and of course a date requester to allow the user to select dates, but the same GUI, file reading/writing, and foreach block management are repurposed to enter, save, load, and display calendar data:

view center-face gui: layout [
    btn "Date" [date/text: form request-date  show date]
    date: field
    text "Event Title:"
    event: field
    text "Time:"
    time: field
    text "Notes:"
    notes: field
    btn "Add Appoinment" [
        write/append %appts.txt rejoin [
            mold date/text newline
            mold event/text newline
            mold time/text newline
            mold notes/text newline 
        ]
        date/text: "" event/text: "" time/text: "" notes/text: ""
        show gui
        alert "Added"
    ]
    a: area
    btn "View Schedule" [
        today: form request-date
        foreach [date event time notes] load %appts.txt [
            if date = today [
                a/text: copy ""
                append a/text form rejoin [
                    date newline
                    event newline
                    time newline
                    notes newline newline
                ]
                show a
            ]
        ]
    ]
]

6.11 Parts Database

Here's an application that allows workers to add, delete, edit, and view manufactured parts. This is another quintessential simple text field storage application. It can be used as shown here, to save parts information, but by adjusting just a few lines of code and text labels, it could be easily adapted to store contacts information, or any other type of related fields of blocked text data. Be sure to pay special attention to how the text-list widget is used, and be particularly aware of how the "pick" function is used to select consecutive values after a found index:

REBOL [title: "Parts]

; The line below writes a new empty data file to the hard drive, if it
; doesn't already exist.  If the file DOES already exist, then this
; function simply writes an empty string to it (i.e., leaves the file
; alone):

write/append %data.txt ""

; This line loads all saved records from the database file:

database: load %data.txt


; Here's the GUI window:

view center-face gui: layout [

    ; Here's a text label to instruct the user:

    text "Load an existing record:"

    ; This text list displays an alphabetically sorted list of the
    ; names found in the database (every forth item).  The number
    ; pair indicates the widget's pixel size:

    name-list: text-list blue 400x100 data (sort extract database 4) [

        ; The following line is included to avoid potential errors.
        ; When an item in the text list is clicked, we first check that
        ; the selected data (represented by the word "value") is NOT
        ; equal to nothing.  If so, exit the widget's action block 
        ; (the "return" word quits the text-list's action routine):

        if value = none [return]

        ; The following code finds the selected part in the loaded
        ; database.  The display fields in the GUI are then set
        ; to show the found part, and each of the 3 items after
        ; it in the database (part name = field 1, manufacturer = 
        ; field 2, SKU = field 3, notes = field 4):

        marker: index? find database value
        n/text: pick database marker
        a/text: pick database (marker + 1)
        p/text: pick database (marker + 2)
        o/text: pick database (marker + 3)

        ; Update the display to show the changed text fields (notice
        ; the "gui" label defined above - it refers to the entire GUI
        ; layout):

        show gui
    ]

    ; Here are the text display fields, and some text labels to show
    ; what should be typed into each field:

    text "Part Name:"       n: field 400
    text "Manufacturer:"    a: field 400
    text "SKU:"             p: field 400
    text "Notes:"           o: area  400x100

    ; The "across" word adds widgets to the GUI next to one another,
    ; instead of beneath one another, which is the default behavior
    ; (the following 3 buttons will appear next to each other):

    across

    ; Here's a GUI button to let the user save the contents of the
    ; text fields to the database:

    btn "Save" [

        ; When this button is clicked, make sure the required field
        ; contains some text.  If not, notify the user, and then exit
        ; this button's routine (the "return" word quits the save 
        ; button's action block):

        if n/text = "" [alert "You must enter a part name." return]

        ; Now run through every forth item in the database to check if
        ; the part already exists.  If so, give the user the option to
        ; overwrite that record.  If they respond yes, delete the old
        ; record from the database ("remove/part" deletes 4 items at
        ; the location where the selected part is found).  If the user
        ; responds no, escape out of the save button's routine:

        if find (extract database 4) n/text [
            either true = request "Overwrite existing record?" [
               remove/part (find database n/text) 4
            ] [
               return
            ]
        ]

        ; Now update the database with the new data, and write it to
        ; the hard drive.  The "repend" function appends the evaluated
        ; variables inside the brackets (in this case a block of 4
        ; separate text strings contained in the GUI fields) to the
        ; database:

        save %data.txt repend database [n/text a/text p/text o/text]

        ; Update the text-list to show the added record:

        name-list/data: sort (extract copy database 4)
        show name-list
    ]

    ; This button allows the user to clear the screen and enter a
    ; new record:

    btn "Delete" [

        ; When this button is clicked, the code below gives the user
        ; the option to delete the selected record.  If the user
        ; selects "yes", the "remove/part" function deletes 4 items
        ; from the database, at the location where the selected part
        ; is found.  The database is saved, and the text fields are
        ; cleared ("do-face" runs the action block of the 
        ; "clear-button" widget above, to clear the GUI fields), then
        ; the part name list is updated:

        if true = request rejoin ["Delete " n/text "?"] [
            remove/part (find database n/text) 4
            save %data.txt database
            do-face clear-button 1
            name-list/data: sort (extract copy database 4)
            show name-list
        ]
    ]

    clear-button: btn "New" [

        ; When this button is clicked, set the text of each field to an
        ; empty string:

        n/text: copy  ""
        a/text: copy  ""
        p/text: copy  ""
        o/text: copy  "" 

        ; As always, when any on data in the GUI is changed, the
        ; screen must be updated: 

        show gui
    ]
]

Here's the whole program without comments:

REBOL [title: "Parts"]
write/append %data.txt ""
database: load %data.txt
view center-face gui: layout [
    text "Parts in Stock:"
    name-list: text-list blue 400x100 data sort (extract database 4) [
        if value = none [return]
        marker: index? find database value
        n/text: pick database marker
        a/text: pick database (marker + 1)
        p/text: pick database (marker + 2)
        o/text: pick database (marker + 3)
        show gui
    ]
    text "Part Name:"       n: field 400
    text "Manufacturer:"    a: field 400
    text "SKU:"             p: field 400
    text "Notes:"           o: area  400x100
    across
    btn "Save" [
        if n/text = "" [alert "You must enter a part name." return]
        if find (extract database 4) n/text [
            either true = request "Overwrite existing record?" [
               remove/part (find database n/text) 4
            ] [
               return
            ]
        ]
        save %data.txt repend database [n/text a/text p/text o/text]
        name-list/data: sort (extract copy database 4)
        show name-list
    ]
    btn "Delete" [
        if true = request rejoin ["Delete " n/text "?"] [
            remove/part (find database n/text) 4
            save %data.txt database
            do-face clear-button 1
            name-list/data: sort (extract copy database 4)
            show name-list
        ]
    ]
    clear-button: btn "New" [
        n/text: copy  ""
        a/text: copy  ""
        p/text: copy  ""
        o/text: copy  ""
        show gui
    ]
]

Here's the same program as above, repurposed as a contacts database app (quite a bit more versatile than the earlier example). The field labels have simply been changed:

REBOL [title: "Contacts"]
write/append %data.txt ""
database: load %data.txt
view center-face gui: layout [
    text "Existing Contacts:"
    name-list: text-list blue 400x100 data sort (extract database 4) [
        if value = none [return]
        marker: index? find database value
        n/text: pick database marker
        a/text: pick database (marker + 1)
        p/text: pick database (marker + 2)
        o/text: pick database (marker + 3)
        show gui
    ]
    text "Name:"       n: field 400
    text "Address:"    a: field 400
    text "Phone:"      p: field 400
    text "Notes:"      o: area  400x100
    across
    btn "Save" [
        if n/text = "" [alert "You must enter a name." return]
        if find (extract database 4) n/text [
            either true = request "Overwrite existing record?" [
               remove/part (find database n/text) 4
            ] [
               return
            ]
        ]
        save %data.txt repend database [n/text a/text p/text o/text]
        name-list/data: sort (extract copy database 4)
        show name-list
    ]
    btn "Delete" [
        if true = request rejoin ["Delete " n/text "?"] [
            remove/part (find database n/text) 4
            save %data.txt database
            do-face clear-button 1
            name-list/data: sort (extract copy database 4)
            show name-list
        ]
    ]
    clear-button: btn "New" [
        n/text: copy  ""
        a/text: copy  ""
        p/text: copy  ""
        o/text: copy  ""
        show gui
    ]
]

6.12 Time Clock and Payroll Report

Here's a time clock program that can be used to log employee punch-in and punch-out times for shift work. The GUI allows for easy addition and deletion of employee names, and a full audit history backup of every entry made to the sign ins, is saved to the hard drive each time any employee signs in or out.

REBOL [title: "Time Clock"]

; First, check to see if an employee file has been created.  If not,
; create it.  This list will be displayed in a text-list widget.  It
; contains the item "(Add New...)", which will be used to allow users to
; add new names to the list:

unless exists? %employees [write %employees {"John Smith" "(Add New...)"}]

; Initialize a current-employee value to an empty string:

cur-employee: copy ""

view center-face layout [

    ; Here's the text list widget that displays the employee names, sorted
    ; alphabetically.  It's labeled "tl1":

    tl1: text-list 400x400 data sort load %employees [

        ; When the user selects a name from the list, set the
        ; "cur-employee" variable to hold the selected name:

        cur-employee: value

        ; If the user selected "(Add New...)", run the code required to
        ; add a name to employee list:

        if cur-employee = "(Add New...)" [

            ; First, request the name from the user, and save the quoted
            ; value to the %employees file:

            write/append %employees mold trim request-text/title "Name:"

            ; Reload the new employee list into the text-list widget, and
            ; update the display:

            tl1/data: sort load %employees  show tl1
        ]
    ]

    ; The "key" widget does not display any face in the GUI.  It just
    ; waits for a key to be pressed, and performs the desired actions:

    key #"^~" [

        ; First, get the name of the employee to be deleted, and assign
        ; it the variable label "del-emp":

        del-emp: copy to-string tl1/picked

        ; Next, load the employee list and assign it the label "temp-emp":

        temp-emp: sort load %employees

        ; Confirm that the user actually wants to delete the employee:

        if true = request/confirm rejoin ["REMOVE " del-emp "?"] [

            ; Find the employee name in the employee list, remove the
            ; name, and assign the variable label "new-list" to the
            ; pruned employee list:

            new-list: head remove/part find temp-emp del-emp 1

            ; Save the pruned employee list to the %employees file:

            save %employees new-list

            ; Update the text-list widget and alert the user that the
            ; action has been completed:

            tl1/data: sort load %employees show tl1
            alert rejoin [del-emp " removed."]
        ]
    ]

    ; Here's a button to allow employees to clock in and out of shifts:

    btn "Clock IN/OUT" [

        ; First make sure that a name is selected.  If not, alert the user
        ; and exit the button's action routine:

        if ((cur-employee = "") or (cur-employee = "(Add New...)")) [
            alert "You must select your name." return
        ]

        ; Concatenate the quoted name and time values inside square
        ; brackets, and beginning with a carriage return.  Assign that
        ; text the variable label "record":

        record: rejoin [
            newline {[} mold cur-employee { "} mold now {"]}
        ]

        ; Confirm with the employee that the selected name and clock time
        ; are correct:

        either true = request/confirm rejoin [
            record " -- IS YOUR NAME AND THE TIME CORRECT?"
        ] [

            ; This routine saves a backup of the current time sheet in
            ; a folder named "clock_history".  First, the folder is
            ; created if it doesn't exist:

            make-dir %./clock_history/

            ; Next, a file name is created by rejoining the folder name
            ; and the current day and time.  Illegal file name characters
            ; are replaced (i.e., "/" and ":" can't be used in file names
            ; on most operating systems).  The text of the existing
            ; %time_sheet.txt file is written to the date stamped backup
            ; file name:

            write rejoin [
                %./clock_history/ 
                replace/all replace form now "/" "--" ":" "_"
            ] read %time_sheet.txt

            ; Write the new record to the %time_sheet.txt file:

            write/append %time_sheet.txt record

            ; Alert the user that the operation is complete:

            alert rejoin [
                uppercase copy cur-employee ", YOUR TIME IS LOGGED."
            ]
        ] [

            ; If the user replied negatively to the confirmation above,
            ; alert the user that the action is cancelled, and exit the
            ; routine:

            alert "CANCELED"
            return

        ]
    ]
]

Here's the whole program without comments:

REBOL [title: "Time Clock"]
unless exists? %employees [write %employees {"John Smith" "(Add New...)"}]
cur-employee: copy ""
view center-face layout [
    tl1: text-list 400x400 data sort load %employees [
        cur-employee: value
        if cur-employee = "(Add New...)" [
            write/append %employees mold trim request-text/title "Name:"
            tl1/data: sort load %employees show tl1
        ]
    ]
    key #"^~" [
        del-emp: copy to-string tl1/picked
        temp-emp: sort load %employees
        if true = request/confirm rejoin ["REMOVE " del-emp "?"] [
            new-list: head remove/part find temp-emp del-emp 1
            save %employees new-list
            tl1/data: sort load %employees show tl1
            alert rejoin [del-emp " removed."]
        ]
    ]
    btn "Clock IN/OUT" [
        if ((cur-employee = "") or (cur-employee = "(Add New...)")) [
            alert "You must select your name." return
        ]
        record: rejoin [
            newline {[} mold cur-employee { "} mold now {"]}
        ]
        either true = request/confirm rejoin [
            record " -- IS YOUR NAME AND THE TIME CORRECT?"
        ] [
            make-dir %./clock_history/
            write rejoin [
                %./clock_history/ 
                replace/all replace form now "/" "--" ":" "_"
            ] read %time_sheet.txt
            write/append %time_sheet.txt record
            alert rejoin [
                uppercase copy cur-employee ", YOUR TIME IS LOGGED."
            ]
        ] [
            alert "CANCELED"
            return
        ]
    ]
]

Here's a program that creates payroll reports of hours worked by employees, logged by the program above, between any selected start and end dates:

REBOL [title: "Payroll Report"]

; Request start and end dates from a user:

timeclock-start-date: request-date
timeclock-end-date: request-date

; Initials a "totals" variable to an empty string.  This string will be
; used to collect (aggregate) the entire output report text:

totals: copy ""

; Load the employee list, and assign it the variable label "names":

names: load %employees

; Load all the saved time sheet information, and assign it the variable
; label "log":

log: load %time_sheet.txt

; Use a foreach loop to collect the log information for each employee:

foreach name names [

    ; Don't try to collect info for the "(Add New...)" entry in the list:

    if name <> "(Add New...)" [

        ; Create a new block to hold report information for the current
        ; employee, initially just containing the employee name.  Assign
        ; the variable label "times" to the block:

        times: copy reduce [name]

        ; Use foreach to loop through every entry in the time sheet log:

        foreach record log [

            ; If the current employee name matches the name in the current
            ; entry in the log file, add the record to the report:

            if name = log-name: record/1 [

                ; Split up the date and time in the current date/time
                ; entry (data/time is the second item in each log entry).
                ; Assign the variable "date-time" to the result:

                date-time: parse record/2 "/"

                ; Convert the date portion of the result above to a REBOL
                ; date value.  Assign the label "log-date" to that value:

                log-date: to-date date-time/1

                ; Convert the time portion of the result above to a REBOL
                ; time value.  Assign the label "log-time" to that value:

                log-time: to-time first parse date-time/2 "-"

                ; If the date in the current timesheet entry is within the
                ; start and end date period selected by the user, add the
                ; current entry to the employee's report:

                if (
                    (log-date >= timeclock-start-date) and 
                    (log-date <= timeclock-end-date)
                ) [
                    append times log-date
                    append times log-time
                ] 
            ]
        ]

        ; Append the employee name and a carriage return to the final
        ; report text:

        append totals rejoin [name ":" newline]

        ; Initialize a sum variable to 0:

        total-hours: 0

        ; Go through the entire collected "times" block created above
        ; to calculate end-times - start-times.  Remember that the first
        ; item in the block was the user's name, so start this process at
        ; the second item:

        foreach [in-date in-time out-date out-time] (at times 2) [

            ; Append some nicely formatted text containing the start and
            ; end days and times, to the final report text:

            append totals rejoin [
                newline 
                "    in: " in-date ", " in-time 
                "  out: " out-date ", " out-time "    "
            ]

            ; Add the total hours worked to the "total-hours" sum.  Wrap
            ; this routine in an error check, just in case a start or end
            ; time is missing:

            if error? try [
                total-hours: total-hours + (out-time - in-time)
            ] [
                alert rejoin [
                    "Missing login or Missing logout: " name
                ]
            ]
        ]

        ; Append the employee's total computed hours to the final report,
        ; along with some concatenated text and carriage returns, to
        ; create a nicely formatted printout: 

        append totals rejoin [
            newline newline
            "    TOTAL HOURS: " total-hours
            newline newline newline
        ]

    ]
]

; Write the final report to a file name containing the start and end dates
; chosen for the report, and open it using Window's "notepad" application
; (you could simply use REBOL's "editor" function to do this):

write filename: copy rejoin [
    %timeclock_report-- timeclock-start-date 
    "_to_" timeclock-end-date ".txt"
] totals
call/show rejoin ["notepad " to-local-file filename]

Here's the whole program without comments:

REBOL [title: "Payroll Report"]
timeclock-start-date: request-date
timeclock-end-date: request-date
totals: copy ""
names: load %employees
log: load %time_sheet.txt
foreach name names [
    if name <> "(Add New...)" [
        times: copy reduce [name]
        foreach record log [
            if name = log-name: record/1 [
                date-time: parse record/2 "/"
                log-date: to-date date-time/1
                log-time: to-time first parse date-time/2 "-"
                if (
                    (log-date >= timeclock-start-date) and 
                    (log-date <= timeclock-end-date)
                ) [
                    append times log-date
                    append times log-time
                ] 
            ]
        ]
        append totals rejoin [name ":" newline]
        total-hours: 0
        foreach [in-date in-time out-date out-time] (at times 2) [
            append totals rejoin [
                newline 
                "    in: " in-date ", " in-time 
                "  out: " out-date ", " out-time "    "
            ]
            if error? try [
                total-hours: total-hours + (out-time - in-time)
            ] [
                alert rejoin [
                    "Missing login or Missing logout: " name
                ]
            ]
        ]
        append totals rejoin [
            newline newline
            "    TOTAL HOURS: " total-hours
            newline newline newline
        ]
    ]
]
write filename: copy rejoin [
    %timeclock_report-- timeclock-start-date 
    "_to_" timeclock-end-date ".txt"
] totals
call/show rejoin ["notepad " to-local-file filename]

6.13 Blogger

This program allows users to create and add entries to an online blog page. The GUI has text fields which allow the user to enter a title, link, and blog text, as well as a button to select an image file which will be uploaded and included in the blog entry. When the "Upload" button is clicked, an HTML code file is created and uploaded to the user's web server, along with the image (you'll learn more about HTML later in the tutorial - for now just pay attention to the fact that a bunch of foreign HTML code is concatenated together with values entered by the user). Be sure to edit the ftp-url and html-url variables to represent actual user account information (you'll need a user name, password, and folder on a web server to run this example).

REBOL [title: "Blogger"]

; Store the blog file name in a variable:

page: "blog.html"

; Store the FTP account address, with username and password:

ftp-url: ftp://user:pass@site.com/public_html/folder/

; Store the blog's web page URL in a variable: 

html-url: join http://site.com/folder/ page

; Create a 1 pixel blank image to upload, for when the user
; doesn't want to upload any image for a given blog entry:

save/png %dot.png to-image layout/tight [box white 1x1]

; Here's the GUI:

view center-face gui: layout [

    ; Display the blog URL in the GUI (the "form" function converts
    ; the URL data type created above, to a string data type required
    ; by the h2 widget):

    h2 (form html-url)

    ; Here's a descriptive header and a text entry field where the user
    ; can enter a title for the blog.  The field is labeled by the
    ; variable word "t":

    text "Title:"       t: field 400

    ; Header and entry field for a URL link to be included in the blog:

    text "Link:"        l: field 400

    ; Header and selection button for an image to be included in the
    ; blog.  When the button is clicked, a file requestor pops up.  The
    ; button's text is set to display the selected file name:

    text "Image:"       i: btn 400 [i/text: request-file show i]

    ; Header and text entry field for the blog text:

    text "Text:"        x: area  400x100

    ; Layout all the following widgets across the screen:

    across

    ; Here's the GUI button which does most of the work:

    btn "Upload" [

        ; When the button is clicked, first try to read the existing
        ; blog text (HTML source).  If it's readable, assign that data
        ; the variable label "existing-text".  If it's not readable,
        ; create the folder and an empty blog file on the FTP server,
        ; then assign the "existing-text" variable an emptry string:

        if error? try [existing-text: read html-url] [
            make-dir ftp-url
            write (join ftp-url page) ""
            existing-text: copy ""
        ]

        ; Assign the variable word "picture" to the image file name
        ; chosen above ("last split-path" trims off the directory path
        ; portion of the file name (i.e., %/C/folder/myimage.jpg would
        ; be trimmed to %myimage.jpg)): 

        picture: last split-path to-file i/text

        ; Write the image to the FTP server:

        write/binary (join ftp-url picture) (read/binary to-file i/text)

        ; Write the following rejoined HTML to the blog file on the FTP
        ; server:

        write (join ftp-url page) rejoin [

            ; First add the title, enclosed in "h1" tags:

            {<h1>} t/text {</h1>}

            ; Now add a link to the uploaded picture, followed by 2
            ; HTML line break tags:

            {<img src="} picture {"><br><br>}

            ; Add the date and time, followed by 5 spaces, no line breaks:

            now/date { } now/time { &nbsp; &nbsp; }

            ; Add a link tag (because there were no line breaks above,
            ; this link appears on the same line as the date and time in
            ; the blog), followed by 2 line breaks:

            {<a href="} l/text {">} l/text {</a><br><br>}

            ; Put the blog text inside a table which takes up 80% of the
            ; screen.  Center the table on the screen (so it's indented).
            ; Use the "pre" tag to make sure that the text is formatted
            ; exactly the way it was typed in by the user (with carriage
            ; returns and spaces as entered into the area widget above),
            ; and use the "strong" tag to bold the text.  Follow that
            ; entire section of HTML with a line break and then a
            ; "horizontal rule" tag (a separator line):

            {<center><table width=80%><tr><td><pre><strong>}
                x/text 
            {</strong></pre></td></tr></table></center><br><hr>}

            ; Add the previously existing blog HTML below the new entry:

            existing-text

        ]

        ; After the blog has been updated, open the blog URL in the
        ; browser:

        browse html-url

    ]

    ; Add a GUI button to open the blog URL in the browser:

    btn "View" [browse html-url]

    ; This GUI button allows the user to edit the existing blog file
    ; (the HTML data created by this program), using REBOL's built in
    ; text editor.  Remember that REBOL's editor has the ability to
    ; read and SAVE data directly to/from FTP files, so this editor
    ; enables the user to actually edit and MAKE CHANGES to the blog
    ; file on the FTP server:

    btn "Edit" [editor (join ftp-url page)]

]

Here's the whole program, without comments:

REBOL [title: "Blogger"]
page: "blog.html"
ftp-url: ftp://user:pass@site.com/public_html/folder/
html-url: join http://site.com/folder/ page
save/png %dot.png to-image layout/tight [box white 1x1]  ; blank image
view center-face gui: layout [
    h2 (form html-url)
    text "Title:"       t: field 400
    text "Link:"        l: field 400
    text "Image:"       i: btn 400 [i/text: request-file show i]
    text "Text:"        x: area  400x100
    across
    btn "Upload" [
        if error? try [existing-text: read html-url] [
            make-dir ftp-url
            write (join ftp-url page) ""
            existing-text: copy ""
        ]
        picture: last split-path to-file i/text
        write/binary (join ftp-url picture) (read/binary to-file i/text)
        write (join ftp-url page) rejoin [
            {<h1>} t/text {</h1>}
            {<img src="} picture {"><br><br>}
            now/date { } now/time { &nbsp; &nbsp; }
            {<a href="} l/text {">} l/text {</a><br><br>}
            {<center><table width=80%><tr><td><pre><strong>}
                x/text 
            {</strong></pre></td></tr></table></center><br><hr>}
            existing-text
        ]
        browse html-url
    ]
    btn "View" [browse html-url]
    btn "Edit" [editor (join ftp-url page)]
]

6.14 FTP Group Chat

This example is a simple chat application that lets users send instant text messages back and forth across the Internet. The chat "rooms" are created by dynamically creating, reading, appending, and saving text files via ftp (to use the program, you'll need access to an available ftp server: ftp address, username, and password. Nothing else needs to be configured on the server). This enables unlimited private conversation spaces that can be used to connect any number of individuals or teams within a group. This program runs entirely in the REBOL console (i.e., there is no graphic user interface - it's all printed text), so it can be used even on simple devices which don't have GUI support. It includes password protected access for administrators to erase chat contents. It also allows users to pause activity momentarily, and requires a username/password to continue (["secret" "password"], in this example case).

REBOL [title: "FTP Chat Room"]

; The following line gets the URL of a text file on the user's web server
; to use for the chat.  The ftp username, password, domain, and filename
; must be entered in the format shown:

webserver: to-url ask trim/lines {
    URL of text file on your server (ftp://user:pass@site.com/chat.txt):  
}

; The following line gets the user's name:

name: ask "Enter your name:  "

; The following line writes some text to the webserver file (obtained 
; above), indicating that the user has entered the chat.  The "/append"
; refinement adds to the existing text in the webserver file (as opposed
; to erasing what's already there).  Using "rejoin", the text written to
; the webserver is the combined value of the user's name, some static
; text, the current date and time, and a carriage return.  If the file
; doesn't exist, it is created.  Any number of "room" files can be
; automatically created on the web server:

write/append webserver rejoin [now ": " name " has entered the room.^/"]

; Now the program uses a "forever" loop to continually wait for user
; input, and to do appropriate things with that input:

forever [

    ; First, read the messages that are currently in the "webserver" text
    ; file, and assign the variable word "current-chat" to that text:

    current-chat: read webserver 

    ; Clear the screen:

    prin "^(1B)[J"

    ; Display a greeting and some instructions:

    print rejoin [ 
        "--------------------------------------------------"
        newline {You are logged in as: } name newline 
        {Type "room" to switch chat rooms.} newline
        {Type "lock" to pause/lock your chat.} newline
        {Type "quit" to end your chat.} newline 
        {Type "clear" to erase the current chat.} newline 
        {Press [ENTER] to periodically update the display.} newline 
        "--------------------------------------------------" newline
    ]

    print rejoin ["Here's the current chat text at: " webserver newline]
    print current-chat

    ; In the line below, the "ask" function is used to get some text from
    ; the user.  The returned text (the text entered by the user) is
    ; assigned the label "entered-text", and concatenated with the user's
    ; name and the text " says: ".  This prepares it to be added to the
    ; webserver file and displayed in the chat.  Notice that the user
    ; must first respond to the "ask" function, before the rejoin
    ; evaluation can occur:

    sent-message: copy rejoin [
        name " says: "
        entered-text: ask "You say:  "
    ]

    ; The "switch" structure below is used to check for commands in the
    ; text entered by the user.  If the user enters "quit", "clear", 
    ; "room", or "lock", appropriate actions occur:

    switch/default entered-text [   ; "switch" handles multiple "if" cases

        ; If the user typed "quit", stop the forever loop (exit the
        ; program):

        "quit" [break] 

        ; If the user typed "clear", erase the current text chat.  But
        ; first, ask user for the administrator username/password:

        "clear" [

            ; "if/else" does the same thing as "either" (deprecated):

            adminu: ask "Admin Username:  "
            adminp: ask "Admin Password:  "
            if/else ((adminu = "secret") and (adminp = "password")) [
                write webserver ""
            ] [
                ask trim/auto {
                    ^LYou must know the administrator password to clear
                    the room!
                }
            ]
        ]

        ; If the user typed "room", request a new FTP address, and run
        ; some code that was presented earlier in the program, using the
        ; newly entered "webserver" variable, to effectively change chat
        ; "rooms":

        "room" [

            ; Add a message the chat file, indicating that the user has
            ; left the chat:

            write/append webserver rejoin [
                now ": " name " has left the room." newline
            ]

            ; Get the URL of a new chat text file (the new room address).
            ; Use the old address as the default displayed URL:

            webserver: to-url ask rejoin [
                {New Web Server Address (} to-string webserver {):  }
            ]

            ; Display a message in the newly chosen chat text file,
            ; showing that the user has entered the chat:

            write/append webserver rejoin [
                now ": " name " has entered the room." newline
            ]

        ]

        "lock" [

            ; Display a message to the user that the program will be
            ; paused:

            ask trim/lines {
                ^LPress [Enter] to resume.  You'll need the correct
                username and password to continue.
            }

            ; Don't go on until the user gets the password right:

            forever [

                ; The while loop below continually asks the user for
                ; a password, until correct:

                while [
                    adminu: ask "Admin Username:  "
                    adminp: ask "Admin Password:  "
                    ((adminu <> "secret") or (adminp <> "password"))
                ][
                    ask "^LIncorrect password - look in the source!"
                ]

                ; After the user has entered the correct username and
                ; password, exit the forever loop and continue with
                ; the program:

                break

            ]
        ]
    ][

        ; The following line is the default case for the switch structure:
        ; as long as the entered message is not blank ([Enter]), write the
        ; entered message to the web server (append it to the current chat
        ; text):

        if entered-text <> "" [
            write/append webserver rejoin [sent-message newline]
        ]
    ]
]

; When the "forever" loop is exited, do the following:

prin "^(1B)[J"   ; clear screen
print "Goodbye!" 
write/append webserver rejoin [now ": " name " has closed chat." newline]
wait 1

The bulk of this program runs within the "forever" loop, and uses the conditional "switch" structure to decide how to respond to user input. This is a classic outline that can be adjusted to match a variety of generalized situations in which the computer repeatedly waits for and responds to user interaction at the command prompt.

6.15 Group Reminder

This program operates along the same lines as the FTP Chat app. It stores reminder notes for a group of users in a text file accessible by FTP. Unlike the FTP chat application, this program makes use of GUI features, and focuses on popping up when new messages are sent to the group. Users can run the program at any time to type a new text reminder into a text area widget. The program can also be started and minimized to run in the background and listen for reminders. In listen mode, a GUI window will pop up with a message whenever someone else in the group adds a new reminder. The system can be used to share event reminders, notes, task lists, or any other relevant and time sensitive information. This app only requires that someone in the group has access to an FTP server. Just like the FTP chat program, nothing needs to be configured on the server. All that's required is a username and password, and a connection to the Internet.

REBOL [title: "Group Reminder System"]

; This variable is set to store the username, password, folder, file and
; URL of the FTP server at which the reminder texts are stored:

group-url: ftp://user:pass@site.com/public_html/reminders.txt

; The request-list function here allows the user to choose between adding
; a new reminder text, or listening in the background.  The user's
; response is stored in the variable "menu":

menu: request-list "" ["Create New Reminder" "Listen For Reminders"]

; The code pattern below was demonstrated earlier in the "Parts" program.
; It creates a new file, if the file doesn't exist.  Otherwise, it does
; nothing:

write/append %reminders.txt ""

; If the user chose to create a new reminder, do the following code:

if menu = "Create New Reminder"  [

    ; Create a GUI window with some header text, an area widget, and a
    ; button:

    view center-face layout [

        h3 "Add a new reminder for the group:"
        a: area wrap
        btn "Submit" [

            ; When clicked, run the following code with an error check,
            ; just in case an Internet connection isn't available:

            if error? try [

                ; Attempt to write the area widget text to the FTP file:

                write/append group-url mold a/text

            ; If there's an error writing, alert the user and quit:

            ] [alert "ERROR: Not Saved (check Internet connection)" quit]

            ; Otherwise, alert with user with a success message, and end:

            alert "Saved"
            quit

        ]
    ]
]

; If the user chose to listen for reminders, do the following code:

if menu = "Listen For Reminders" [

    ; Print a waiting message in the console.  This can be minimized:

    print "Listening for reminders..."

    ; Repeat the following code endlessly:

    forever [

        ; Waiting a few seconds saves a lot of bandwidth:

        wait 5

        ; "Attempt" is just like "if error? try" - it just doesn't do
        ; anything if an error occurs.  The point of attempting the
        ; following code is to ensure the program continues to run if
        ; the Internet connection is disabled, or the FTP file can't be
        ; read for any other reason:

        attempt [

            ; Read the text in the FTP file, and assign it the label
            ; "reminders":

            reminders: read group-url

            ; If a new reminder has been added by anyone in the group,
            ; the "reminders" text will not match the text stored in the
            ; file reminders.txt:

            if reminders <> read %reminders.txt [

                ; If that's the case, update the reminders.txt file, with
                ; the new text read from the FTP file:

                write %reminders.txt reminders

                ; Create a blank string to store the current reminders:

                remind: copy {}

                ; Reverse the order of all reminders in the FTP file, so
                ; that the newest messages are first, then loop through
                ; them with the "foreach" function:

                foreach reminder (reverse load reminders) [

                    ; Append each reminder to the blank text string
                    ; created above, separated by 2 blank lines:

                    append remind rejoin [reminder newline newline]

                ]

                ; Open a GUI window and display the formatted reminder
                ; text in an area widget:

                view center-face layout [
                    h3 "Reminders for the group:"
                    area remind
                ]

            ]
        ]
    ]
]

Here's the whole program without comments:

REBOL [title: "Group Reminder System"]
group-url: ftp://user:pass@site.com/public_html/reminders.txt
menu: request-list "" ["Create New Reminder" "Listen For Reminders"]
write/append %reminders.txt ""
if "" = read group-url [write group-url {""}]
if menu = "Create New Reminder"  [
    view center-face layout [
        h3 "Add a new reminder for the group:"
        a: area wrap
        btn "Submit" [
            if error? try [
                write/append group-url mold a/text
            ] [alert "ERROR: Not Saved (check Internet connection)" quit]
            alert "Saved"
            quit
        ]
    ]
]
if menu = "Listen For Reminders" [
    print "Listening for reminders..."
    forever [
        wait 5
        attempt [
            reminders: read group-url
            if reminders <> read %reminders.txt [
                write %reminders.txt reminders
                remind: copy {}
                foreach reminder (reverse load reminders) [
                    append remind rejoin [reminder newline newline]
                ]
                view center-face layout [
                    h3 "Reminders for the group:"
                    area remind
                ]
            ]
        ]
    ]
]

6.16 A Univeral Report Generator, For Paypal and any other CSV Table Data

This example creates reports on columns and rows of data in a .csv table. The script demonstrates typical CSV file operations using parse, foreach, and simple series functions. The code performs sums upon columns, and selective calculations upon specified fields, based upon conditional evaluations, searches, etc. Practical column and row based reporting capabilities such as this are a simple and useful skill in REBOL. Using basic permutations of techniques shown here, it's easy to surpass the capabilities of spreadsheets and other "office" reporting tools.

Actual data for use in testing this example can be downloaded as follows:

  1. Log into your Paypal account
  2. Click on My Account -> History -> Download History
  3. Pick a range of dates
  4. Select "Comma Delimited - All Activity" (where it's labeled "File Types to Download")
  5. Save the file to %Download.csv.

At the time this example code was created, the author's CSV file download contained the following fields ("A" through "AP" - 42 columns).

Date, Time, Time Zone, Name, Type, Status, Currency, Gross, Fee, Net, From Email Address, To Email Address, Transaction ID, Counterparty Status, Address Status, Item Title, Item ID, Shipping and Handling Amount, Insurance Amount, Sales Tax, Option 1 Name, Option 1 Value, Option 2 Name, Option 2 Value, Auction Site, Buyer ID, Item URL, Closing Date, Escrow Id, Invoice Id, Reference Txn ID, Invoice Number, Custom Number, Receipt ID, Balance, Address Line 1, Address Line 2/District/Neighborhood, Town/City, State/Province/Region/County/Territory/Prefecture/Republic, Zip/Postal Code, Country, Contact Phone Number

The code automatically handles tables with any arbitrary number of columns, allowing fields to be referred to by labels present in the first line of the .csv file.

The script is simple to understand:

REBOL [title: "Paypal Reports"]

; First, read in the lines of the CSV file
; (as described earlier in the CSV/parse section of this tutorial):

filename: request-file/only/file %Download.csv
lines: read/lines filename

; The first row contains column labels.  Let's convert that CSV line to a
; block, using the parse/all function:

labels: copy parse/all lines/1 ","

; Remove extra spaces from each of the labels in the "labels" block:

foreach label labels [trim label]

; Now we'll convert the CSV lines into a REBOL data block.  First,
; create an empty block to store the data:

database: copy []

; The data values start at line two of the CSV file.  Use foreach and
; parse/all to separate the individual values in each line, and collect
; them into a block of blocks (as described in the CSV/parse section):

foreach line (at lines 2) [
    parsed: parse/all line ","
    append/only database parsed
]

; For the first report, let's get a list of every person in the "Name"
; Column.  Find the index number of the "Name" column in the "labels"
; block.  We'll use that to pick out name values from each row:

name-index: index? find labels "Name"

; Create an empty text string to collect the names:

names: copy {}

; Loop through the database, picking the item at the name-index location
; from each row

foreach row database [
    append names rejoin ["Name:  " (pick row name-index) newline]
]

; Display the results:

editor names

; Now let's view every transaction in which the name field includes
; "Netflix".  It's basically the same routine as above, only now with an
; added conditional evaluation that uses the "find" function.  And for
; this report, I want to see the amount paid.  I'll set a variable to
; refer to the index position of the "Net" column:

net-index: index? find labels "Net"
amounts: copy {}
foreach row database [
    if find/only (pick row name-index) "Netflix" [
        append amounts rejoin ["Amount:  " (pick row net-index) newline]
    ]
]
editor amounts

; Now, let's get a sum of every Netflix transaction between January and
; December, 2012.  The dates are stored in a column labeled "Date", with
; a format like: "12/26/2012" (month/day/year).  We'll need to convert
; that to REBOL's internal format (day-month-year)

date-index: index? find labels "Date"

; You've seen earlier how to collect sums.  Start by setting a sum
; variable to 0.  We'll add values to the sum to get a total:

sum: $0

; Now loop through the database and perform some conditional evaluations
; on every row:

foreach row database [
    if find/only (pick row name-index) "Netflix" [

        ; We'll use "parse" to separate the date text at the
        ; "/" character:

        date: parse (pick row date-index) "/"

        ; Pick the month using the values in system/locale/months

        month:  pick system/locale/months to-integer date/1

        ; Then rearrange and put back together the date pieces using
        ; "rejoin":

        reb-date: to-date rejoin [date/2 "-" month "-" date/3]

        ; If the date is within the chosen range, add the value to
        ; the sum:

        if ((reb-date >= 1-jan-2012) and (reb-date <= 31-dec-2012)) [
            sum: sum + (to-money pick row net-index)
        ]
    ]
]

; Show the answer:

alert form sum

Here's the entire program without comments:

REBOL [title: "Paypal Reports"]
filename: request-file/only/file %Download.csv
lines: read/lines filename
labels: copy parse/all lines/1 ","
foreach label labels [trim label]
database: copy []
foreach line (at lines 2) [
    parsed: parse/all line ","
    append/only database parsed
]
name-index: index? find labels "Name"
names: copy {}
foreach row database [
    append names rejoin ["Name:  " (pick row name-index) newline]
]
editor names
net-index: index? find labels "Net"
amounts: copy {}
foreach row database [
    if find/only (pick row name-index) "Netflix" [
        append amounts rejoin ["Amount:  " (pick row net-index) newline]
    ]
]
editor amounts
date-index: index? find labels "Date"
sum: $0
foreach row database [
    if find/only (pick row name-index) "Netflix" [
        date: parse (pick row date-index) "/"
        month:  pick system/locale/months to-integer date/1
        reb-date: to-date rejoin [date/2 "-" month "-" date/3]
        if ((reb-date >= 1-jan-2012) and (reb-date <= 31-dec-2012)) [
            sum: sum + (to-money pick row net-index)
        ]
    ]
]
alert form sum

If you want to use this example to create reports for any other CSV file, just copy and paste the first part of the script. It loads and parses a user selected CSV file, and creates a block of labels from the first line:

REBOL [title: "Reports"]
filename: request-file/only/file %filename.csv
lines: read/lines filename
labels: copy parse/all lines/1 ","
foreach label labels [trim label]
database: copy []
foreach line (at lines 2) [
    parsed: parse/all line ","
    append/only database parsed
]

You can use this line of code to view the list of column labels in the CSV file:

editor labels

Next, assign variable(s) to the column label(s), on which you want to perform computations:

name-index: index? find labels "Name"
date-index: index? find labels "Date"
net-index: index? find labels "Net"

Set any initial variables needed to perform computations (sum, max/min, etc.), or to hold blocks of collected values:

sum: $0
names: copy {}
amounts: copy {}

Use foreach loop(s) to perform conditional evaluations and desired computations on every row of data:

foreach row database [
    append names rejoin ["Name:  " (pick row name-index) newline]
]
foreach row database [
    if find/only (pick row name-index) "Netflix" [
        append amounts rejoin ["Amount:  " (pick row net-index) newline]
    ]
]
foreach row database [
    if find/only (pick row name-index) "Netflix" [
        date: parse (pick row date-index) "/"
        month:  pick system/locale/months to-integer date/1
        reb-date: to-date rejoin [date/2 "-" month "-" date/3]
        if ((reb-date >= 1-jan-2012) and (reb-date <= 31-dec-2012)) [
            sum: sum + (to-money pick row net-index)
        ]
    ]
]

Display all the computed or collected results:

editor names
editor amounts
alert form sum

Of course, the computations above involve quite a bit of evaluation and data processing, in order to demonstrate useful reusable code snippets (such as converting dates to REBOL values that can be manipulated intelligently). In most cases, simple sums, averages, searches, and other common computations will require far less code. You can shorten code even further by using numbers to refer to columns. Simple reports rarely require much more code than the first example in this tutorial:

sum: $0
foreach line at read/lines http://re-bol.com/Download.csv 2 [
    sum: sum + to-money pick (parse/all line ",") 8
]
alert form sum

6.17 Reviewing and Using the Code You've Seen To Model New Applications

You're already well on your way to understanding how to build useful business applications. At this point, it's wise to go back and review every section in the tutorial. The perspective you have now will help to clarify the value of concepts that were skimmed during a first read. Focus on experimenting with individual lines of code, memorizing functions, and understanding the details of syntax that may have been confusing the first time around. Try repurposing, altering, and editing the complete programs you've seen to far, to be useful in data management activities that apply to your own interests. Here are some ideas for experimentation:

  1. Add columns to data blocks in the existing apps (i.e, perhaps "email" and "mobile", "home", "work" fields to the contacts examples, or "name" a "title" fields to messages in the reminder app).
  2. Add new computations to the reporting examples (perhaps average, max, and min functions to columns in the Paypal reports).
  3. Apply the CSV, sorting, computing, and reporting code patterns you've seen to columns of data exported from other desktop applications and web sites.
  4. Apply new and more complex conditional operations to computations (perhaps apply tax only to items in a Paypal file that were shipped from a certain state, or apply a fee to prices of items that are made by a certain manufacturer in the "Parts" database app).
  5. Create a few small GUI apps that save CSV files which can be imported into a spreadsheet (perhaps add a CSV export feature to the "Contacts" or "Parts" examples, and especially try exporting computed reports as CSV files).
  6. Add list features to the email program (perhaps allow email addresses to be chosen from a contact list, or send emails to a group of users).
  7. Add useful features to the file editor and web page editor programs (maybe try storing a history of edited files, or FTP login credentials).
  8. Combine the Inventory and Cash Register programs, so that users can select inventory items from a drop down list in the cash register app.
  9. Add unique computation routines to the calculator app.
  10. Experiment with the "parse" and "find" functions (perhaps try adding a search feature to the schedule and email programs, or send pre-formed responses to email messages that contain a given string of text in the subject).
  11. Experiment with printing and displaying formatted data in the console and in GUI fields (perhaps build an email program that parses the header of each email message, and displays each part on separately printed lines in the console or in separate area widgets in a GUI).
  12. Add image and file sharing features to the Group Reminders app.
  13. Add images to stored records in the Parts database app.
  14. Build GUI versions of the FTP chat and Paypal Reports applications. Use text-list widgets to display messages in chat and to select column names and computation options in reports.
  15. Experiment with GUI layouts. Position text headers, fields, buttons, areas, text lists, etc. in ways that allow data to be arranged coherently and pleasantly on screen, and which invite intuitive user interactions and natural work flow patterns.
  16. Experiment with how colors, fonts, widget sizes, images, and other cosmetic features can be used to change the appearance of applications.

You'll see much more about how to approach tasks like this, as the tutorial progresses, but exploring creatively and learning to use the tools you've seen so far, will go a long way towards building fundamental coding ability. If you learn nothing more than the code presented up to this point, you will already be able to create a wide variety of practical business applications that would be impossible to implement quite so personally using generic off-the-shelf software products. Continue learning, and that potential will increase dramatically.

7. User Defined Functions and Imported Code Modules

7.1 "Do", "Does", and "Func"

REBOL's built-in functions satisfy many fundamental needs. To achieve more complex or specific computations, you can create your own function definitions.

Data and function words contained in blocks can be evaluated (their actions performed and their data values assigned) using the "do" word. Because of this, any block of code can essentially be treated as a function. That's a powerful key element of the REBOL language design:

some-actions: [
    alert "Here is one action." 
    print "Here's a second action."
    write %/c/anotheraction.txt "Here's a third action."
    alert "Writing to the hard drive was the third action."
]

do some-actions

New function words can also be defined using the "does" and "func" words. "Does" is included directly after a word label definition, and forces a block to be evaluated every time the word is encountered:

more-actions: does [
    alert "Counting some more actions:  4" 
    alert "And another:  5"
    alert "And finally:  6"
]

; Now, to use that function, just type the word label:

more-actions

Here's a useful function to clear the command line screen in the REBOL interpreter.

cls: does [prin "^(1B)[J"]

cls

7.1.1 "Func"

The "func" word creates an executable block in the same way as "does", but additionally allows you to pass your own specified parameters to the newly defined function word. The first block in a func definition contains the name(s) of the variable(s) to be passed. The second block contains the actions to be taken with those variables. Here's the "func" syntax:

func [names of variables to be passed] [
    actions to be taken with those variables
]

This function definition:

sqr-add-var: func [num1 num2] [print square-root (num1 + num2)]

Can be used as follows. Notice that no brackets, braces, or parentheses are required to contain the data arguments. Data parameters simply follow the function word, on the same line of code:

sqr-add-var 12 4      ; prints "4",  the square root of 12 + 4  (16)
sqr-add-var 96 48     ; prints "12", the square root of 96 + 48 (144)

Here's a simple function to display images:

display: func [filename] [view layout [image load to-file filename]]

display (request-file)

7.2 Return Values

By default, the last value evaluated by a function is returned when the function is complete:

concatenate: func [string1 string2] [join string1 string2]

string3: concatenate "Hello " "there."
print string3

You can also use the word "return" to end the function with a return value. This can be helpful when breaking out of loops (the "for" function performs a count operation - it will be covered in depth in a later section of this tutorial):

stop-at: func [num] [
    for i 1 99 1 [
        if (i = num) [return i]
        print i
    ]
    return num
]
print stop-at 38

7.3 Scope

By default, values used inside functions are treated as global, which means that if any variables are changed inside a function, they will be changed throughout the rest of your program:

x: 10

change-x-globally: func [y z] [x: y + z]

change-x-globally 10 20
print x

You can change this default behavior, and specify that any value be treated as local to the function (not changed throughout the rest of your program), by using the "/local" refinement:

x: 10

change-x-locally: func [y z /local x] [x: y + z]

change-x-locally 10 20     ; inside the function, x is now 30
print x                    ; outside the function, x is still 10

You can specify refinements to the way a function operates, simply by preceding optional operation arguments with a forward slash ("/"):

compute: func [x y /multiply /divide /subtract] [
    if multiply [return x * y]
    if divide   [return x / y]
    if subtract [return x - y]
    return x + y
]

compute/multiply 10 20
compute/divide 10 20
compute/subtract 10 20
compute 10 20

7.4 Function Documentation

The "help" function provides usage information for any function, including user defined functions:

help for
help compute

You can include documentation for any user defined function by including a text string as the first item in it's argument list. This text is included in the description displayed by the help function:

doc-demo: func ["This function demonstrates doc strings"] [help doc-demo]
doc-demo

Acceptable data types for any parameter can be listed in a block, and doc strings can also be included immediately after any parameter:

concatenate-string-or-num: func [
    "This function will only concatenate strings or integers."
    val1 [string! integer!] "First string or integer"
    val2 [string! integer!] "Second string or integer"
] [
    join val1 val2
]

help concatenate-string-or-num
concatenate-string-or-num "Hello " "there."  ; this works correctly
concatenate-string-or-num 10 20              ; this works correctly
concatenate-string-or-num 10.1 20.3          ; this creates an error

7.5 Doing Imported Code

You can "do" a module of code contained in any text file, as long as it contains the minimum header "REBOL [ ]" (this includes HTML files and any other files that can be read via REBOL's built-in protocols). For example, if you save the previous functions in a text file called "myfunctions.r":

REBOL []  ; THIS HEADER TEXT MUST BE INCLUDED AT THE TOP OF ANY REBOL FILE

sqr-add-var: func [num1 num2] [print square-root (num1 + num2)]
display: func [filename] [view layout [image load filename]]
cls: does [prin "^(1B)[J"]

You can import and use them in your current code, as follows:

do %myfunctions.r

; now you can use those functions just as you would any other
; native function:

sqr-add-var
display
cls

Here's an example function that plays a .wave sound file. Save this code as C:\play_sound.r:

REBOL [title: "play-sound"]  ; you can add a title to the header

play-sound: func [sound-file] [
    wait 0
    ring: load sound-file
    sound-port: open sound://
    insert sound-port ring
    wait sound-port
    close sound-port
]

Then run the code below to import the function and play selected .wav files:

do %/c/play_sound.r

play-sound %/C/WINDOWS/Media/chimes.wav
play-sound to-file request-file/file %/C/WINDOWS/Media/tada.wav

Imported files can contain data definitions and any other executable code, including that which is contained in additional nested source files imported with the "do" function. Any code or data contained in a source file is evaluated when the file is "do"ne.

7.6 Separating Form and Function in GUIs - The Check Writer App

One common use for functions is to help keep GUI layout code clean and easy to read. Separating widget layout code from action block code helps to clarify what each widget does, and simplifies the readability of code which lays out screen design.

For example, the following buttons all perform several slightly different actions. The first button counts from 1 to 100 and then alerts the user with a "done" message, the second button counts from 101 to 200 and alerts the user when done, the third button counts from 201 to 300 and alerts the user when done (the "for" function performs a count operation):

view layout [
    btn "Count 1" [
        for i 1 100 1 [print i]
        alert "Done"
    ]
    btn "Count 2" [
        for i 101 200 1 [print i]
        alert "Done"
    ]
    btn "Count 3" [
        for i 201 300 1 [print i]
        alert "Done"
    ]
]

The action blocks of each button above can all be reduced to a common function that counts from a start number to an end number, and then alerts the user. That function can be assigned a label, and then only that label needs to be used in the GUI widget action blocks:

count: func [start end] [
    for i start end 1 [print i]
    alert "Done"
]
view layout [
    btn "Count 1" [count 1 100]
    btn "Count 2" [count 101 200]
    btn "Count 3" [count 201 300]
]

In large applications where the actions can become complex, separating function code from layout code improves clarity. You'll see this outline often:

action1: func [args] [
    actions
    actions
    actions
]
action2: func [args] [
    other actions
    other actions
    other actions
]
action3: func [args] [
    more actions
    more actions
    more actions
]
view layout [
    widget [action1]
    widget [action2]
    widget [action3]
]

Here's a simple check writing example that takes amounts and names entered into an area widget and creates blocks of text to be written to a check. One function is created to "verbalize" the entered amounts for printing on the check (it converts number values to their spoken English equivalent, i.e., 23482194 = "Twenty Three million, Four Hundred Eighty Two thousand, One Hundred Ninety Four"). Another function is created to loop through each bit of raw check data and to create a block containing the name, the numerical amount, the verbalized amount, some memo text, and the date. The GUI code consists of only 4 lines:

REBOL [title: "Check Writer"] 
verbalize: func [a-number] [
    if error? try [a-number: to-decimal a-number] [
        return "** Error **  Input must be a decimal value"
    ]
    if a-number = 0 [return "Zero"]
    the-original-number: round/down a-number
    pennies: a-number - the-original-number
    the-number: the-original-number
    if a-number < 1 [
        return join to-integer ((round/to pennies .01) * 100) "/100"
    ] 
    small-numbers: [
        "One" "Two" "Three" "Four" "Five" "Six" "Seven" "Eight"
        "Nine" "Ten" "Eleven" "Twelve" "Thirteen" "Fourteen" "Fifteen"
        "Sixteen" "Seventeen" "Eighteen" "Nineteen"
    ]
    tens-block: [
        { } "Twenty" "Thirty" "Forty" "Fifty" "Sixty" "Seventy" "Eighty"
        "Ninety"
    ]
    big-numbers-block: ["Thousand" "Million" "Billion"]    
    digit-groups: copy []
    for i 0 4 1 [
        append digit-groups (round/floor (mod the-number 1000))
        the-number: the-number / 1000
    ]    
    spoken: copy ""
    for i 5 1 -1 [
        flag: false
        hundreds: (pick digit-groups i) / 100
        tens-units: mod (pick digit-groups i) 100
        if hundreds <> 0 [
            if none <> hundreds-portion: (pick small-numbers hundreds) [
                append spoken join hundreds-portion " Hundred "
            ]
            flag: true
        ]
        tens: tens-units / 10
        units: mod tens-units 10
        if tens >= 2 [
            append spoken (pick tens-block tens)
            if units <> 0 [
                if none <> last-portion: (pick small-numbers units) [
                    append spoken rejoin [" " last-portion " "]
                ]
                flag: true
            ]
        ]
        if tens-units <> 0 [
            if none <> tens-portion: (pick small-numbers tens-units) [
                append spoken join tens-portion " "
            ]
            flag: true
        ]
        if flag = true [
            commas: copy {}    
            case [
                ((i = 4) and (the-original-number > 999999999)) [
                    commas: {billion, }
                ]
                ((i = 3) and (the-original-number > 999999)) [
                    commas: {million, }
                ]
                ((i = 2) and (the-original-number > 999)) [
                    commas: {thousand, }
                ]
            ]
            append spoken commas
        ]
    ]
    append spoken rejoin [
        "and " to-integer ((round/to pennies .01) * 100) "/100"
     ]
    return spoken
]
write-checks: does [
    checks: copy []
    data: to-block a1/text
    foreach [name amount] data [
        check: copy []
        append/only checks reduce [
            rejoin ["Pay to the order of: "  name  "   "]
            rejoin ["$"  amount  newline]
            rejoin ["Amount: " verbalize amount newline]
            rejoin ["Sales for November    "  now/date  newline newline]
        ]
    ]
    a2/text: form checks
    show a2
]
view layout [
    text "Amounts and Names:"
    a1: area {"John Smith" 582 "Jen Huck" 95 "Sue Wells" 71 "Joe Lask" 38}
    btn "Create Check Data" [write-checks]
    a2: area
]

One of the clear benefits of using functions is that you don't have to remember, or even understand, how they work. Instead, you only really need to know how to use them. In the example above, you don't have to understand exactly how all computations in the "verbalize" function work. You just need to know that if you type "verbalize (number)", it spits out text representing the specified dollar amount. You can use that function in any other program where it's useful, blissfully unaware of how the verbalizing magic happens. Just paste the verbalize code above, and use it like any other function built into the language. This is true of any function you create, or any function that someone else creates. Working with functions in this way helps improve code re-usability, and the power of the language, dramatically. It also encourages clear code structures that others can read more easily.

Note: The verbalize algorithm was partially derived from the article at http://www.blackwasp.co.uk/NumberToWords.aspx (C# code):

7.7 A Full Featured Group Note Sharing App

In the previous section, the "Group Reminders" and "FTP Chat" applications demonstrated how to save text messages to a web server, so they can be shared with a group of connected users. This application builds on the same idea, adding a number of useful features. The message list display can be updated manually or automatically, at any chosen interval. A repeated beep can be played as an alarm to notify users of new messages (a beep is created with the code: call "echo ^G"). Beep notifications can be turned on and off. Messages are stamped with a time and date, and numbered. Messages can be erased individually by number, or the entire note list can be removed at once. An unlimited number of private "rooms" can be created, simply by changing the URL. A new file will be automatically created at the entered URL, if it doesn't exist.

All of the features in this program are implemented as separate functions. The "update" function, in particular is called not only when the user clicks the update button, but also by other functions, any time a change is made which requires updating the display (when erasing messages, when autoupdate is turned on, etc). Notice that the GUI layout is kept clean, and each widget simply calls a function:

REBOL [title: "Group Notes"]
url: ftp://user:pass@site.com/public_html/Notes
beep: false   autoupdt: false   call ""
write/append %notes.txt ""
update: does [
    if error? try [notes: copy read/lines url] [write url notes: ""]
    if ((beep = true) and (notes <> read/lines %notes.txt)) [
        loop 4 [call "echo ^G" wait 1]
    ]
    write/lines %notes.txt notes
    display: copy {}
    count: 0
    foreach note reverse notes [
        either note = "" [
            note: newline
        ] [
            count: count + 1
            note: rejoin [count ") "note]
        ]
        append display note
    ]
    a/text: display
    if a/text = "" [a/text: copy " "]
    show a
]
autoupdate: does [
    either autoupdt: not autoupdt [
        time: request-text/title/default "Refresh display (seconds):" "10"
        b/text: join "Auto Update:  " autoupdt  show b
        forever [
            either autoupdt = true [wait to-integer time update] [break]
        ]
    ] [
        b/text: join "Auto Update:  " autoupdt  show b
    ]
]
submit: does [
    if f/text = "" [focus f  return]
    if error? try [
        write/lines/append url rejoin [
            "^/^/" now " (" n/text "):  " f/text
        ]
    ] [alert "ERROR: Not Saved (check Internet connection)" return]
    update
    f/text: copy ""  show f  focus f
]
erase: func [arg] [
    if true = request rejoin ["Really erase " arg "?"] [
        write/lines to-file replace/all replace form now "/" "--" ":" "_"
            notes
        if arg = "all" [write url ""]
        if arg = "" [
            indx: (
                3 * to-integer request-text/title/default "Index:" "1"
            ) - 2
            remove/part at notes indx 3 
            write/lines url reverse notes 
        ]
        update
    ]
]
changeurl: does [
    url: to-url u/text  
    update
    focus f
]
setbeep: does [
    beep: not beep  
    p/text: join "Beep: " beep
    show p
]
insert-event-func [either event/type = 'close [quit][event]] 
view center-face layout [
    h3 "Current notes for:"
    u: field 600 form url [changeurl]
    a: area 600x260
    h3 "Name:"
    n: field 600
    h3 "New Note:"
    f: field 600 [submit]
    across
    btn "Update" [update]
    b: btn join "Auto Update: " autoupdt [autoupdate]
    p: btn join "Beep: " beep [setbeep]
    btn "Erase" [erase ""]
    btn "Erase All" [erase "all"]
    do [update focus f]
]

Later in this text, a web based CGI version of this application will be presented, so that users can view and enter notes with either this desktop version of the program, or with a browser based interface, to share and interact with the exact same live data on any platform. Enabling different interfaces can be useful on mobile OSs or on any system where an executable program can't be installed.

8. A Few Useful Data Visualization Tools

8.1 Displaying and Sorting Data Using Spreadsheet-Like GUI Grids

As you've already seen in the "Contacts" example, it's possible to dynamically construct GUIs using foreach loops, to display data in GUI fields. We'll build on examples such as the following in a later chapter:

REBOL [title: "Display a Table of Data"]

; Build 500 rows of 3 columns of random data:
x: copy[] for i 1 500 1[append x reduce [i random "abcd" random 1-1-2012]]

; Display it:
grid: copy [across space 0]
foreach [indx text date] x [
    append grid compose [
        field 50 (form indx)
        field 70 (form text)
        field 110 (form date)
        return
    ]
]
view center-face layout [
    across
    g: box 230x200 with [pane: layout/tight grid pane/offset: 0x0]
    scroller [g/pane/offset/y: g/size/y - g/pane/size/y * value show g]
]

Using raw building blocks of GUI field widgets, even the simple example above requires quite a bit of thought to display a small grid filled with table data, and normal features such as column resizing, sorting, etc., require advanced coding skill. To load, display, sort, and save flat lists and blocked table data, the following compressed code is provided to simplify the required code. Just define a block of header labels, assign the variable label "x" to your grid data, and include the compressed grid code, and you've got a fully functional data grid:

REBOL [title: "Table/Grid/Listview Example"]

headers: ["Numbers" "Text" "Dates"]

x: [
    [1   "1"   1-1-2012]
    [11  "11"  1-2-2012]
    [2   "2"   1-3-2012]
]

do decompress #{
789CC518C98EDB36F4AEAF78500FB11228B2074D0AA8B3A01F904BAF860EB245
D9CAD0A2225133720CFF7B1F77D24BE324456A60C626F9F69D1C5B4A86015E4A
3A922778B3199B7445D9FA1996F6670E8763118D21E004CB298735EBF6B02CCE
4EC9AEE3FB74E8CA3581A5B7C8615E447B8D3741B46674DCB5430E94B41BBE7D
822D292BD20F91FA36FC25F8E118F5A423258706341E2C23C04FD975A4ADC0C7
819E7C664D0BCB781B237C9C713271888BA83821CD9946F0B7A355734AEFCDB0
1F38D945949595DA22550EF5D8AE615995BC4CEB8612C87AF26524032FB4644D
0D7AC783CACD9E5C65ACA5FB4C625B8842A9C5B9309D26253ED672FA5B08E3B0
2CD8B065AF401BB9161A0FE50BF945320B56C2A6E1194C2885B45C4D4BFECBCD
56A3BDAE98CAC5303870D663C82C606682B29E929388331FC12908D265119C0B
529F610E33839EC22241D2211517C28E1E740DFEAB279835F00E3E271060845C
14B2B40826554FAA11D3CE91B2B09E8E3692FE3D68FE37775D720A29D75BE851
CAE9C47EDA78B5D51D819CD24E43119B4E8B7A72BAB29EA7CA4546DBBA21B432
0A92866F490F128CF55814726819F7D69E4062335BB35D57F618F79A5A092BA4
35C3DA5582A49CC02388E54A2F9594C50FD0B9BF484719CEF8B4889E0956E075
CF28350AAA555AEED8D85A4F0E69C7B01ACB2F0CBB00C6B85A1D3EBAF4C0EC58
6A44BB5584D0F798030666AE2B05CD842F0CB32CA01788AF7F0C14F5E8C9D07C
25E9A66F6C25EB48BF262D2F37C468213A970043DAB268672F0D79CD501942DA
B4C6369475654BB2452680E04F9194F3692E516983012BB6B345EE2FE02D383E
279077B9E598DD2131AFDF4948AE85E9D18A15AAE951F5B4F6BB4D92681369CC
126D54363D2C3EFA6C25CCD84AE564EEA314A0561D6F18561B212FD2142A032D
F76CE4E0357865CBC259B56E30D92B46861FB1A3C4F0DC03336B14A1A7AF750A
EF1709B22DAB2AA54D4B0CD3B014600B9E647F6E50890DE698A927A29567BCE1
58552A529723C5C6FE5755A9E163C082228BC46F79EC178F9D4F89BDF4E9DA45
B4E0040F22447BC2C7BE5501DA92D754910C6BFB597B083C278ABBAE478E80C2
8F639D15ED4030B7A5CB44EE4E5280C48777992B9CB363588AFF2343FD8D7439
0345348FE1E76C8407BC1F09DC3FDA0E6007AFBF150B88552B535A42FC141721
0D254A60095FFD33E52512A355FA5D7A7F123CEA9EEDBE2B38844B6E60A3C90B
BB7AC4D138B399A1206C970086CECC882E7792DBEDF929B4A625736E5161B20C
855126358089D5C66F0C3BAC5463D7511C08825E475E48FB84718B851F9BA1C8
75EC8F0C1BDFEBB6E1A2D2FA7B77BFCFDFCBBF0F1F9404122FD7E8EF5489370A
B6ACC52BC297DC28E2F31026CD4DB600991A6EEDA2DD8256BB20D4DD1C99CF3D
01E4A1EA2F6BDBBC3C1692F717116E44CCA6036D2A34F65E8C2DDA0CED062BBD
9D06B0DF12BF3B3762E701DE8C1DF635373D288238318AFB831E46826B442DF9
BB99643DAAF29CDF88E90B6070E1F1012ED5A230287CA94BCAD38ABD62540DBC
94C2E31493034E69753D104F3C214D8AF1A0653C0463573F7CC5D140F8B96E7A
8CD4966C4A8E898CB54F51C442EFD14F02648C3BE90ED36BC335621AEA01165A
7966D44E2CEEA5DD5B2860642E12ADF3299DF0EC766A9764F24FF0F7454ADBAB
525D3BB926D329BC91E8F2FE35796485D04E399DC44E288939C1E21EED2FBCAC
530112C4101C9CA78E36826FC691FC8E10AE2F86B748CC4B0187C11A6CDB6075
E11F5EB590A8854173DD9FB640F3A95828F5C905448C59A46A785064B04EF7AE
C4B093023363508A81D1543E6C0AB5AC69A26BE8CD5C6F190F19664AB59B4B58
7869D53532E873A691AAC3E0B6182AF9EDA1514EDD29CCA70FF3C88E856E86C6
A39919783FCEFD693A89BE3511FFD0A86DEE25105CF0641F066B66D1B5223DD8
B9195A154429B5151F4ABC350D628693CF5FE666211DAF59C36AE49CB5560B25
2476315861F83FAB1E0B2BECDCD1B71EBD9C2C6650B03E39887FDB23621E72C3
F888C301354F5B4396E319D48450701DF028E604317059979EB1928C0C79FBB6
2173F1DC44B9D156E916F7312CFE9850D72014A5B91FECD483D32366E2536C1F
19F797225CE5A1BE8EA9FB9A0B07FF2E2D6DBF2694828C5E0D2015B74969A1CF
FDF7B34E101F44D4AE90721C3D35507DF3702AE799C15E211C6139A5AA53F45A
7199BB71DC05971DF4C3801AF6C08E7DFAA299EBBBBE78E5A0DA7C3A2FFC7BF9
5B252884CED06E385EE3FA4CF6E26FCD2AA43A765884DC7304A40BF35A118089
F12404BC0CD761894BCF68DECDAF039F5356D0C7C87BF1B6CFC2764FBD093BD5
CC83F03FD2FC2B1641170000
}
view center-face gui: layout gui-block

Other options such as coloring rows, and specifying column data types, using the compressed table code above, are demonstrated in the following example. This is a critically useful tool for data entry, visualization, and demonstration:

REBOL [title: "Table/Grid/Listview Example With Expanded Features"]

headers: ["Numbers" "TEXT (Note Sort)" "Dates"] ; REQUIRED COLUMN LABELS

; ALL THESE ADDITIONAL SETUP PARAMETERS ARE *** OPTIONAL ***:

x: [[1 "1" 1-1-2012][11"11"1-2-2012][2"2"1-3-2012]]  ; some default data

colors: [blue black red]    ; specify column colors like this
empty-space: 235            ; size of blank GUI area to appear below grid
svv/vid-face/color: white   ; default GUI face color

; Here's how to include GUI layout code to appear above the grid: 

gui-block: {
    h3 "RIGHT-CLICK/DRAG HEADERS TO RESIZE COLUMNS.  RESIZE WINDOW..."
    text "Click headers to sort (note that sort is DATA-TYPE SPECIFIC)."
    text "Notice Arrow Keys, PgUp/PgDn Keys, Scroll Bar, and highliting"
    text "Click any cell to edit data. Buttons load and save data to HD."
}

; The following line automatically fits grid to resized GUI window:

insert-event-func [either event/type = 'resize [resize-fit none] [event]]

do decompress #{
    789CC518C98EDB36F4AEAF78500FB11228B2074D0AA8B3A01F904BAF860EB245
    D9CAD0A2225133720CFF7B1F77D24BE324456A60C626F9F69D1C5B4A86015E4A
    3A922778B3199B7445D9FA1996F6670E8763118D21E004CB298735EBF6B02CCE
    4EC9AEE3FB74E8CA3581A5B7C8615E447B8D3741B46674DCB5430E94B41BBE7D
    822D292BD20F91FA36FC25F8E118F5A423258706341E2C23C04FD975A4ADC0C7
    819E7C664D0BCB781B237C9C713271888BA83821CD9946F0B7A355734AEFCDB0
    1F38D945949595DA22550EF5D8AE615995BC4CEB8612C87AF26524032FB4644D
    0D7AC783CACD9E5C65ACA5FB4C625B8842A9C5B9309D26253ED672FA5B08E3B0
    2CD8B065AF401BB9161A0FE50BF945320B56C2A6E1194C2885B45C4D4BFECBCD
    56A3BDAE98CAC5303870D663C82C606682B29E929388331FC12908D265119C0B
    529F610E33839EC22241D2211517C28E1E740DFEAB279835F00E3E271060845C
    14B2B40826554FAA11D3CE91B2B09E8E3692FE3D68FE37775D720A29D75BE851
    CAE9C47EDA78B5D51D819CD24E43119B4E8B7A72BAB29EA7CA4546DBBA21B432
    0A92866F490F128CF55814726819F7D69E4062335BB35D57F618F79A5A092BA4
    35C3DA5582A49CC02388E54A2F9594C50FD0B9BF484719CEF8B4889E0956E075
    CF28350AAA555AEED8D85A4F0E69C7B01ACB2F0CBB00C6B85A1D3EBAF4C0EC58
    6A44BB5584D0F798030666AE2B05CD842F0CB32CA01788AF7F0C14F5E8C9D07C
    25E9A66F6C25EB48BF262D2F37C468213A970043DAB268672F0D79CD501942DA
    B4C6369475654BB2452680E04F9194F3692E516983012BB6B345EE2FE02D383E
    279077B9E598DD2131AFDF4948AE85E9D18A15AAE951F5B4F6BB4D92681369CC
    126D54363D2C3EFA6C25CCD84AE564EEA314A0561D6F18561B212FD2142A032D
    F76CE4E0357865CBC259B56E30D92B46861FB1A3C4F0DC03336B14A1A7AF750A
    EF1709B22DAB2AA54D4B0CD3B014600B9E647F6E50890DE698A927A29567BCE1
    58552A529723C5C6FE5755A9E163C082228BC46F79EC178F9D4F89BDF4E9DA45
    B4E0040F22447BC2C7BE5501DA92D754910C6BFB597B083C278ABBAE478E80C2
    8F639D15ED4030B7A5CB44EE4E5280C48777992B9CB363588AFF2343FD8D7439
    0345348FE1E76C8407BC1F09DC3FDA0E6007AFBF150B88552B535A42FC141721
    0D254A60095FFD33E52512A355FA5D7A7F123CEA9EEDBE2B38844B6E60A3C90B
    BB7AC4D138B399A1206C970086CECC882E7792DBEDF929B4A625736E5161B20C
    855126358089D5C66F0C3BAC5463D7511C08825E475E48FB84718B851F9BA1C8
    75EC8F0C1BDFEBB6E1A2D2FA7B77BFCFDFCBBF0F1F9404122FD7E8EF5489370A
    B6ACC52BC297DC28E2F31026CD4DB600991A6EEDA2DD8256BB20D4DD1C99CF3D
    01E4A1EA2F6BDBBC3C1692F717116E44CCA6036D2A34F65E8C2DDA0CED062BBD
    9D06B0DF12BF3B3762E701DE8C1DF635373D288238318AFB831E46826B442DF9
    BB99643DAAF29CDF88E90B6070E1F1012ED5A230287CA94BCAD38ABD62540DBC
    94C2E31493034E69753D104F3C214D8AF1A0653C0463573F7CC5D140F8B96E7A
    8CD4966C4A8E898CB54F51C442EFD14F02648C3BE90ED36BC335621AEA01165A
    7966D44E2CEEA5DD5B2860642E12ADF3299DF0EC766A9764F24FF0F7454ADBAB
    525D3BB926D329BC91E8F2FE35796485D04E399DC44E288939C1E21EED2FBCAC
    530112C4101C9CA78E36826FC691FC8E10AE2F86B748CC4B0187C11A6CDB6075
    E11F5EB590A8854173DD9FB640F3A95828F5C905448C59A46A785064B04EF7AE
    C4B093023363508A81D1543E6C0AB5AC69A26BE8CD5C6F190F19664AB59B4B58
    7869D53532E873A691AAC3E0B6182AF9EDA1514EDD29CCA70FF3C88E856E86C6
    A39919783FCEFD693A89BE3511FFD0A86DEE25105CF0641F066B66D1B5223DD8
    B9195A154429B5151F4ABC350D628693CF5FE666211DAF59C36AE49CB5560B25
    2476315861F83FAB1E0B2BECDCD1B71EBD9C2C6650B03E39887FDB23621E72C3
    F888C301354F5B4396E319D48450701DF028E604317059979EB1928C0C79FBB6
    2173F1DC44B9D156E916F7312CFE9850D72014A5B91FECD483D32366E2536C1F
    19F797225CE5A1BE8EA9FB9A0B07FF2E2D6DBF2694828C5E0D2015B74969A1CF
    FDF7B34E101F44D4AE90721C3D35507DF3702AE799C15E211C6139A5AA53F45A
    7199BB71DC05971DF4C3801AF6C08E7DFAA299EBBBBE78E5A0DA7C3A2FFC7BF9
    5B252884CED06E385EE3FA4CF6E26FCD2AA43A765884DC7304A40BF35A118089
    F12404BC0CD761894BCF68DECDAF039F5356D0C7C87BF1B6CFC2764FBD093BD5
    CC83F03FD2FC2B1641170000
}

; APPEND ANY WIDGETS AND/OR GUI CODE TO APPEAR BELOW THE GRID, HERE:

append gui-block [

    ; REPLACE 'BTN' WITH 'KEY' TO HIDE BTNS AND STILL USE KEY SHORTCUTS.
    ; CHANGE/REMOVE BUTTONS AND/OR KEYBOARD SHORTCUTS AS NEEDED:

    text "" return
    btn "Insert (Ins)" keycode [insert] [add-line] 
    btn "Remove (Del)" #"^~" [remove-line]  
    btn "Move (CTRL+M)" #"^M" [move-line]
    btn "Grow (+)" #"+" [resize-grid 1.333]
    btn "Shrink (-)" #"-" [resize-grid .75]
    btn "Fit (CTRL+R)" #"^R" [resize-fit]
    return
    btn "Load Blocked (CTRL+O)" #"^O" [load-blocked/request %blocked.txt]
    btn "Save Blocked (CTRL+S)" #"^S" [save-blocked/request %blocked.txt]
    btn "Load Flat (CTRL+U)" #"^U" [load-flat/request %flat.txt]
    btn "Save Flat (CTRL+F)" #"^F" [save-flat/request %flat.txt]

; LOAD A DEFAULT DATA *FILE HERE (instead of specifying it in code above):
; Not that the "load-flat" and "save-flat" functions load "flat" blocks,
; which are simply long sequences of data values.  The "load-blocked" and
; "save-blocked" functions load block which have rows enclosed inside
; deliniated blocks.  All of those functions provide an optional
; "/request" refinement that allows the user to select a file:

    ;  do [load-blocked %blocked.txt] 

]
view/options center-face gui: layout gui-block [resize]

Details about how to build GUI grids from native REBOL code, including the compressed code above, will be examined fully in later sections of this tutorial. For now, the general solution above is immediately functional, and can be applied to the majority of situations where a visual grid tool is required to enter, display, sort, load, save, and otherwise manipulate table data.

8.2 Creating Graphs, Plots, and Charts with "Q-Plot"

REBOL's complete graphics toolkit will be fully explored in detail, in future sections of this tutorial. For the moment, the "q-plot" dialect by Matt Licholai is a simple solution for creating bar, line, pie and other charts from block data. You can download and run the q-plot dialect like this:

REBOL []
if not exists? %q-plot.r [write %q-plot.r read http://re-bol.com/q-plot.r]
do %q-plot.r

Once q-plot is downloaded, graphing a block of values is as simple as this:

view quick-plot [
    600x400                            ; set the program window size
    bars [5 3 8 2 10 3 4 9 5 7]        ; set graph type and data to plot
]

Using the code above, here's a complete bar graph example:

REBOL [title: "Minimal Bar Graph Example"]
if not exists? %q-plot.r [write %q-plot.r read http://re-bol.com/q-plot.r]
do %q-plot.r
view quick-plot [
    600x400
    bars [5 3 8 2 10 3 4 9 5 7]
]

Notice that the q-plot dialect syntax looks very much like REBOL's build in VID dialect for building GUIs. The primary difference is that "view layout" is replaced with "view quick-plot". Here's an example that demonstrates how to adjust colors, add text labels, and attach scales for each XxY data axis:

REBOL [title: "Another Bar Graph Example"]
if not exists? %q-plot.r [write %q-plot.r read http://re-bol.com/q-plot.r]
do %q-plot.r
view center-face quick-plot [
    600x300
    y-min 0                           ; minimum value to display on y axis
    fill-pen blue                     ; set fill color
    pen green                         ; set outline and text color
    bar-width 80                      ; set bar width
    bars [5 3 8 2 10 3 4 9 5 7]
    pen black                         ; set outline and text color
    label "Fat Bars"                  ; optionally add labels
    y-axis 11                          
    x-axis 10
]

Pie charts are just as simple to create. Here's a pie chart example with 2 specified sections of the pie "exploded" out for emphasis (the "explode [3 5]" code is optional):

REBOL [title: "Exploded Pie Chart"]
if not exists? %q-plot.r [write %q-plot.r read http://re-bol.com/q-plot.r]
do %q-plot.r
view center-face quick-plot [
    400x400
    pie [10 3 6 1 8] labels [A B C D E] explode [3 5]
    title "Exploded Sections C and E" style vh2
]

Line graphs are also simple to create:

REBOL [title: "Simple Line Graph Example"]
if not exists? %q-plot.r [write %q-plot.r read http://re-bol.com/q-plot.r]
do %q-plot.r
view quick-plot [
    400x400
    line [1 2 4 8 16 32 64 128 256]
]

Here's a more complex line graph example that demonstrates how to plot a predefined block of data, how to add a title, how to add text with a font and defined position (up and over a percentage of the window), and how to attach a scaled grid to the display:

REBOL [title: "Another Line Graph Example"]
if not exists? %q-plot.r [write %q-plot.r read http://re-bol.com/q-plot.r]
do %q-plot.r
my-block: copy [2]
loop 10 [append my-block (2 * last my-block)]
option-font: make face/font [
    size: 30
    style: [italic bold underline]
    name: font-serif
]
view center-face quick-plot [
    500x500
    scale linear 
    line [(data: copy my-block)]
    title style vh1 "Linear scale"
    x-axis 7 border
    y-axis 7 border
    x-grid 7
    y-grid 7
    text font option-font "Formatted Text" color red up 50 over 40
]

Here's an extension of the "Paypal Reports" program you've seen earlier in this text. It plots all the gross transaction numbers using a bar graph, and makes a pie chart of transactions with Saoud Gorn:

REBOL [title: "Paypal Reports Charts"]
transactions: copy []
saoud: copy []
dates: copy []
foreach line at read/lines http://re-bol.com/Download.csv 2 [
    row: parse/all line ","
    append transactions to-integer row/8
    if find row/4 "Saoud" [
        append saoud to-integer row/8
        append dates replace row/1 "/2012" ""
    ]
]
if not exists? %q-plot.r [write %q-plot.r read http://re-bol.com/q-plot.r]
do %q-plot.r
view quick-plot [
    594x400
    bars [(data: copy transactions)]
    label "All Paypal Transactions"
]
view center-face quick-plot [
    495x530
    pen blue
    pie [(data: copy saoud)] labels [(data: copy dates)] explode [1 2 3]
    title "Saoud" style vh2     
]

This example demonstrates how to include several plots in one window. The default alignment for multi-plots is vertical. The "multi-plot/across" refinement lays them out horizontally:

REBOL [title: "Multi-Plots"]
if not exists? %q-plot.r [write %q-plot.r read http://re-bol.com/q-plot.r]
do %q-plot.r
m-plots: multi-plot/across 594x200 [ 
    [
        title "2 to a Power"
        pen green 
        line [0 2 4 8 16 32 64 128] 
    ]
    [
        title "Rizing"
        pen white
        line [0 5 10 15 20 25] 
    ]
    [
        title "Falling"
        pen blue    
        line [25 20 15 10 5 0] 
    ] 
]
view m-plots

This example demonstrates how to place plots in sub-panels for easy switching:

REBOL [title: "Switching Plots"]
if not exists? %q-plot.r [write %q-plot.r read http://re-bol.com/q-plot.r]
do %q-plot.r    
window: layout [
    vh2 "Switching Plots"
    guide 
    pad 20
    button "Sine Wave"   [graph/pane: plot1 show graph]
    button "Parabola"    [graph/pane: plot2 show graph]
    button "Cubic Curve" [graph/pane: plot3 show graph]
    return
    box 2x204 blue
    return
    graph: box 354x204 coal
]
data1: copy []
data2: copy []
data3: copy []
for i -400 400 .5 [
    append data1 sine i
    append data2 (i * i)
    append data3 (i ** 3)
]
graph-size: 350x200
plot1: quick-plot [
    (graph-size)
    line [(data1)]
    title "Sine Wave"
]
plot2: quick-plot [
    (graph-size)
    line [(data2)]
    title "Parabola"
]
plot3: quick-plot [
    (graph-size)
    line [(data3)]
    title "Cubic Function"
]
plot1/offset: 2x2
plot2/offset: 2x2
plot3/offset: 2x2
graph/pane: plot1
view window

Be aware that instead of downloading and running the q-plot dialect from an external file, you can include the compressed q-plot code directly in your program:

REBOL [title: "Q-Plot Compressed"]
do decompress #{
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1B073E630E25058B45EF4862E9686EB3A3DA378996DF40C30426DCDFCC7871B5
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DA68D7FD0168A2B4806D36AD3AE8E6B719863ADFD526CDDEECD298D3968ACF60
2C66DF444AD2719D9124DCEF47E56D16508DEB230B0A1C25B9311E5D3C559F04
5B6F6515D763DF0989520E7F58D1373FCDA8CF4DF21E7522D8240242456E35BD
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8BC7C221552A60FC42FB3E6561CC521315B70B4AAEB81F7B3350DC01A00976C8
75C62431700DDB03037A2AA3423468A7BAA92E5F6D24C54594BF6F568E6BF902
01ABC358589D0E9B98EB056C576C89A9D4AD12DAFE20B4FD516847CDD0E4D821
E0D348ED8FDBA8C93E009600C11E961D1DFD729C8E6E178D54B861CACAAA7BAE
7819E0B3D01EC1F44AE00CD3525830DC05DC2638404C91B4DA34159330F23E80
013F8FC2E8837EF4613FFAD3FAD107FDE8C37EF4A7F563C13EB7A5943FBA02E1
F85FF161B13CBDB18DF389C6465CF93C188B7D357147DE48EAEABEF3268DD670
DA6A43CB816DD159D5837319FE7A4CEDCA06EFB8493EBB86D2EC518A6952E726
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C73C9EB214B94E792591EA96C093A301B6C166CA636B68612DB010E6392E2D0E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09F2022EFDFA83A8702889BB2CDE9A84313E1F81A6CF3481C27B6B0A770C7678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}
view quick-plot [
    400x400
    line [1 2 4 8 16 32 64 128 256]
]

A complete tutorial about all of q-plot's features is available by downloading and running the "ez-plot" tutorial from rebol.org:

write %ez-plot.r read http://www.rebol.org/library/scripts/ez-plot.r
do %ez-plot.r

8.3 Drawing Charts Using Raw GUI Code

It should be noted that creating bar charts using native REBOL GUI elements is as simple as drawing box widgets, each sized to the numerical value of items in a list:

REBOL [title: "Simplest Bar Chart Maker"]
data: [12 3 9 38 1 23 18]
gui: copy [backdrop white]
foreach val data [append gui compose [box blue (as-pair (val * 10) 40)]]
view layout gui

The code below adds a number of features such as text labels, randomly colored bars, and a 3D look using buttons instead of box widgets:

REBOL [title: "Simple Bar Chart Maker"]
data: [12 3 9 38 1 23 18]
labels: [Jan Feb Mar Apr May Jun Jul]
gui: copy [backdrop white across]
repeat i length? data [
    append gui compose [
        text bold 30 (form labels/:i)
        button random white (as-pair (data/:i * 12) 40) (mold data/:i)
        return
    ]
]
view layout gui

This example adds variables for auto scaling and sizing, a gradient and colored grid background pattern, and vertical bar layout:

REBOL [title: "Simple Bar Chart Maker"]

data: [12 3 9 38 1 23 18]
labels: ["Jan" "Feb" "Mar" "Apr" "May" "Jun" "Jul"]
height: 11
width: 50

gui: copy [
    backdrop effect [
        gradient 1x1 180.255.255 255.255.100 grid 10x10 220.220.189
    ]
    across
]
foreach val reverse data [
    append gui compose [
        button random white (as-pair width (val * height))
    ]
]
chart: to-image layout gui
gui2: [
    backdrop white
    style txt text bold (width)
    tabs 20
    across image (chart) effect [rotate 180] return tab
] 
foreach label labels [append gui2 compose [txt (label)]] 
view center-face layout gui2

8.4 Creating 3D Graphs With r3D

A tutorial about the 3D library "r3D" by Andrew Hoadley is covered at http://re-bol.com/rebol.html#section-9.6. A nice business use example of r3D is available by running this code:

do http://www.rebol.net/demos/BF02D682713522AA/histogram.r

The following example demonstrates how to edit code in histogram.r to create 3D graphs using a block of your own revelent data. This can provide a nice flourish for displaying data graphs in presentation settings. You can use the "asdfghqwerty" keys to adjust the camera position of the 3d view. Simply load your data into the "graph-data" block:

REBOL [title: "3D Graph"]

; Here is where you put your block of data to be graphed.
; The first column contains labels for each value.
; The second column contains the actual values to be graphed.

graph-data: [
    ["Jan"  11.0]
    ["Feb"  22.0]
    ["Mar"  25.0]
    ["Apr"  55.0]
    ["May"  35.0]
    ["Jun"  75.0]
    ["Jul"  20.0]
    ["Aug"  33.0]
    ["Sep"  21.0]
    ["Oct"  55.0]
    ["Nov"  65.0]
    ["Dec"  45.0]
]

; This compressed code is the r3D module.  You never need to touch it:

do to-string decompress 64#{
eJzFWluP2zYWft5/weYl9gSOTUm2x0a2i23aAQq0m0VTZMcWhEAjcTJqdKskq2P/
+j28UxSVmXR3sQHGEs/147lQpJRffvju3U9h1PjpIktJ2WXdeY9C/HqFVtbfV9CY
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PcOlJACJO07oTDnLY8Mfy/uKK7+N8+REv+XcAPkfrKBb7YDrygiP3ekk6PzJXbYK
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bupI7NECr+AfLN3wmGL7rG8lL1QylE4fY3TL5eR7gu9P8IEuK0tnSSZDvi+1ssiX
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k33KSiibU8kXnYtdXFxiPzMWhit4Tq7n94NiFwChoIxqpNSMUj3uAbYEyFGb9Jdn
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XezJC74GwzZHotkrIx51Lh69kuZTGqEYNU0eOmXye25GLKBcnw/UOsA+iEMt5WrE
srxHa7BVk5gHSkUoNNPBQyhfyYFOVy3ERpzveQUubnJenJ+QoFU+Ly5PS0FBCZSS
wtY6yIJjpSseGe/s5J0Z7+LkXYTNNypAoY6UsurmSrtu7iUSsZWFxdcMWWE3VfMr
VBitRNGNwwAIZai1mcyLoQJN5s0HeeJFLg/1GMI1EftpHvh6lgRkxk4N1XDAjOwT
ie7HmWyrhYoemE1Od7CDZvvjMGT/D0b8V42IDRZqtHAMB6Liz9DDQz080GPfy8Ej
tMQGdNAGeVHowWVLL1uovdCHyzW9XKMgCgO4rOlljXAUXgNvQy8bSsTIowoY+SAZ
Rf8G28Udt8glAAA=
}

; This compressed code is some initial preparation to enable plotting.
; You never need to touch it either:

do decompress #{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}

; The user definable GUI layout goes here.  If you want to use other
; key controls, or widgets such as sliders to control the view angle
; and size of the 3D view, put that code here.  The "cameraTrans_" and
; "cameraLookat_" variables make all the adjustments: 

out: layout [
    origin 1x5
    at 0x0 scrn: box 400x360 black effect [draw RenderTriangles]
    across
    text "" #"a" [cameraTransx: (cameraTransx + 10) update show scrn]
    text "" #"s" [cameraTransx: (cameraTransx - 10) update show scrn]
    text "" #"d" [cameraTransy: (cameraTransy + 10) update show scrn]
    text "" #"f" [cameraTransy: (cameraTransy - 10) update show scrn]
    text "" #"g" [cameraTransz: (cameraTransz + 10) update show scrn]
    text "" #"h" [cameraTransz: (cameraTransz - 10) update show scrn]
    text "" #"q" [cameraLookatx: (cameraLookatx + 10) update show scrn]
    text "" #"w" [cameraLookatx: (cameraLookatx - 10) update show scrn]
    text "" #"e" [cameraLookaty: (cameraLookaty + 10) update show scrn]
    text "" #"r" [cameraLookaty: (cameraLookaty - 10) update show scrn]
    text "" #"t" [cameraLookatz: (cameraLookatz + 10) update show scrn]
    text "" #"y" [cameraLookatz: (cameraLookatz - 10) update show scrn]
]

; Try changing the variables below to affect whether the lables and values
; are shown at the bottom of each 3D bar in the graph, and whether or not
; the data is shown in color or black and white:

DisplayLabel: true
DisplayValue: true
ColouredLabels: false

; The following 2 lines update and show the display.  Don't change them:

update 
view out

8.5 Using the Google Chart API

Google.com provides a powerful and nice looking chart generator which is freely accessible by anyone, at http://https://developers.google.com/chart/. The syntax for preparing chart data and displaying results is dramatically simplified using the REBOL script at http://reb4.me/r/google-charts.r/, by Chris Ross Gill. To use it, just include the line "do http://reb4.me/r/google-charts.r" in your script, or paste the following code:

REBOL[title: "Google Chart API"]
#{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}

That code enables a simple REBOL dialect to create and display charts:

REBOL [title: "Google Chart Introduction"]
do http://reb4.me/r/google-charts.r
probe chart [
    title: "Chart Example"
    type: 'line
    size: 350x150
    labels: ["Red" "Green" "Blue"]
    data: [50 40 10]
    colors: reduce [red green blue]
    area: [color solid 244.244.240]
]
halt

The block of chart properties is easy to understand. Edit it to include your ownd data values, title, chart type, size, labels, colors, etc. To create the chart above using the native Google API, you'd need to learn how write the following code (paste this into any web browser, all as 1 line, and you'll see the chart appear):

http://chart.apis.google.com/chart?cht=p3&chs=350x150&
chd=t:50,40,10&chtt=Chart%20Example&chco=ff0000,00ff00,
0000ff&chl=Red|Green|Blue&chf=bg,s,f4f4f0

You can view the results of the REBOL "chart" function using the "browse" function:

REBOL [title: "Google Chart Introduction"]
do http://reb4.me/r/google-charts.r
browse chart [
    title: "Chart Example"
    type: 'pie
    size: 350x150
    labels: ["Red" "Green" "Blue"]
    data: [50 40 10]
    colors: reduce [red green blue]
    area: [color solid 244.244.240]
]

Or view it directly in a GUI by loading the results into an "image" widget:

REBOL [title: "Google Chart Introduction"]
do http://reb4.me/r/google-charts.r
my-chart: chart [
    title: "Chart Example"
    type: 'line
    size: 350x150
    labels: ["Red" "Green" "Blue"]
    data: [50 40 10]
    colors: reduce [red green blue]
    area: [color solid 244.244.240]
]
view layout [image load my-chart]

Changing the properties is easy:

REBOL [title: "Another Google Chart"]
do http://reb4.me/r/google-charts.r
my-chart: chart [
    title: "Chart 2"
    type: 'pie
    size: 500x400
    labels: ["John" "Paul" "Sue"]
    data: [35 55 10]
    colors: reduce [orange purple pink]
    area: [color solid 225.225.245]
]
view layout [image load my-chart]

You can include REBOL code directly in the chart block to perform calculations, format data, etc:

REBOL [title: "Example by Chris Ross Gill"]
do http://reb4.me/r/google-charts.r
clipdata: {Adsense Revenue^-300
Sponsors^-500
Gifts^-50
Others^-58}

browse chart [
    title: "Revenue"
    size: 650x300
    type: 'pie

    ; extract raw data
    data: parse/all clipdata "^/^-"
    labels: extract data 2
    data: extract/index data 2 2

    ; format data and labels
    sum: 0
    forall data [sum: sum + data/1: to-integer data/1]
    forall data [change data round 100 * data/1 / sum]
    forall labels [
        labels/1: rejoin [labels/1 " " data/(index? labels) "%"]
    ]
]

More information about the REBOL Google Chart API is available at http://www.ross-gill.com/page/Google_Charts_and_REBOL.

8.5.1 Working with Other Web Site APIs

Chris has created a number of other web APIs that make easy work of interacting with popular sites such as Twitter, Facebook, and Etsy. A tutorial about using REBOL with the Etsy API is available here. You can read more about using REBOL with the Twitter API, and simplifying the use of Rest, OAuth, and other protocols at http://www.ross-gill.com/page/REBOL

8.6 Using the "Nano-Sheets" Spreadsheet App

In the introductory demos section of this text, you saw a small spreadsheet app titled "Rebocalc". This application idea was extended in an article by Steve Irvin and Steve Shireman at http://www.devx.com/opensource/Article/27454. The resulting "Nano-Sheets" app is actually useful in production situations and can be improved using simple REBOL code. Saving, loading, printing, and other features are already available in the Nano-Sheets app. You can create your own functions that use any of the features of the REBOL language to process cell data (math, graphics, parse, native dialogs and GUI interfaces, Internet connectivity, file and network protocols to connect with data sources, etc.). This program and the free REBOL interpreter are so small that they can both be sent easily, even by email, to others who may need to use it. No large or expensive office software installations are required to run spreadsheets created with this tool.

Here's a slightly modified version, with scroll bars, for grids of any size. Column sum and row sum functions are also added the included abilities:

REBOL [Title: "Nano-Sheets Spreadsheet"]
cell-size:  125x20
sheet-size: 10x50
window-size: 800x450
scalar-types: [
    integer! | decimal! | money! | time! | date! | tuple! | pair!
]
protect 'scalar-types
sheet: lay: current-file: sheet-code: none
cells: copy [] 
sheet-buttons: copy []
use [
    buttons== cell== sheet-code==
    id val text action face style
] [
    id: val: text: action: face: none
    style: 'btn 
    buttons==: [
        'buttons into [
            any [
                set val word! (id: val) 2 [
                    set val string! (text: val)
                    | set val block! (action: val)
                ] (
                    repend sheet-buttons [id text action]
                    append lay/pane face: make-face/size/offset style
                        cell-size
                        cells/:id/offset
                    if 'button = style [face/edge/size: 1x1]
                    if not none? face [
                        face/text: text
                        face/action: action
                        face/style: style
                    ]
                )
            ]
        ]
    ]
    cell==: [
        set id word! into [
            opt 'formula set val [block! | path!](cells/:id/formula: :val)
            | opt 'value set val [string! | scalar-types] (
                set cells/:id/var cells/:id/text: val
            )
        ]
    ]
    sheet-code==: ['do set sheet-code block! (do sheet-code)]
    sheet==: [
        (sheet-code: none  clear sheet-buttons)
        opt sheet-code==
        any [buttons== | cell==]
    ]
]
if link? [
    hilight-all: func [face] [
        either empty? face/text [unlight-text] [
            highlight-start: head face/text
            highlight-end: tail face/text
        ]
    ]
]
clear-cell: func [cell] [set cell/var cell/text: cell/formula: none]
clear-sheet: does [
    foreach [id cell] cells [clear-cell cell]
    clear next find lay/pane last cells
    show lay
]
compute: does [
    unfocus
    foreach [id cell] cells [
        if cell/formula [
            if error? try [cell/text: do cell/formula] [
                cell/text: "ERROR!"
            ]
            set cell/var cell/text
            show cell
        ]
    ]
]
cur-cell: does [either in-cell? [system/view/focal-face] [none]]
empty-cell?: func [cell] [
    all [
        none? cell/formula
        any [
            none? cell/text
            all [string? cell/text empty? cell/text]
        ]
    ]
]
enter: func [face /local data] [
    if empty? face/text [exit]
    set face/var face/text
    data: either #"=" = face/text/1 [next face/text][face/text]
    if error? try [data: load data] [exit]
    if scalar? :data [face/formula: none  set face/var data  exit]
    face/formula: either formula? face/text [compose [(:data)]] [none]
]
event-func: func [face event /local f] [
    if all ['key = event/type in-cell?] [
        switch event/key [
            F2    [if in-cell? [show-formula system/view/focal-face]]
            up    [move up]
            down  [move down]
        ]
    ]
    event
]
formula?: func [text] [#"=" = text/1]
in-cell?: has [f] [all [f: system/view/focal-face 'cell = f/style]]
load-sheet: func [file [file! url!]] [
    clear-sheet
    parse load/all file sheet==
    current-file: file
    show lay
    compute
]
move: func ['way /local pos] [
    pos: find cells cur-cell
    cell: pick switch way [
        up    [enter cur-cell  skip pos negate sheet-size/x * 2]
        down  [enter cur-cell  skip pos sheet-size/x * 2]
    ] 1
    if not object? cell [cell: none]  ; if 'A1 = cell [cell: cells/A1]
    if cell [focus cell]
]
new-sheet: does [
    clear-sheet
    current-file: none
    show lay
    focus second cells
]
use [not-vals] [
    not-vals: reduce [none ""]
    no-val?: func [cell-val] [find not-vals cell-val]
]
open-sheet: func [/with file [file! url!]] [
    if not file [
        if %none = file: to-file request-file [exit]
    ]
    load-sheet file
    focus second cells
]
save-sheet: func [/as /local file buffer] [
    if any [not file: current-file  as] [
        if %none = file: to-file request-file/save [exit]
    ]
    if all [file <> current-file  exists? file] [
        if not confirm join file { already exists. 
            Do you want to write over it?} [exit]
    ]
    buffer: copy []
    if sheet-code [repend buffer ['do sheet-code]]
    if not empty? sheet-buttons [repend buffer ['buttons sheet-buttons]]
    foreach [id cell] cells [
        if not empty-cell? cell [
            repend buffer [
                cell/var reduce [any [cell/formula  get cell/var]]
            ]
        ]
    ]
    save file buffer
    current-file: file
]
scalar?: func [val] [find scalar-types type?/word :val]
set-cell: func [id val /local cell] [
    cell: select cells id
    cell/text: form val  enter cell  show cell
    compute
]
show-formula: func [face] [
    if face/formula [
        face/text: join "=" mold/only face/formula
        focus face
    ]
]
ctx-html-export: context [
    out-buff: make string! 10'000
html-template: {
<html>
<!--Page generated by REBOCalc-->
<head>
<title>$title</title>
<style type="text/css">
html, body, p, td, li {font-family: arial, sans-serif, 
    helvetica; font-size: 10pt;}
table, tr {border-collapse: collapse;}
th, td {font-size: 12px; border: 1px solid #C0C0C0; 
    padding: 0.5em 0.5em 0;}
th {background: #8E806E; font-weight: bold; 
    text-align: center; color: #404040;}
</style>
</head>
<body bgcolor="white">
$table
</body></html>
}
    emit: func [data] [repend out-buff [reduce data newline]]
    set 'emit-html func [/to file /local val] [
        clear out-buff
        emit <table>
        repeat row 1 + sheet-size/y [
            emit [<tr><th> either 1 = row [""] [form row - 1]</th>]
            repeat col sheet-size/x [
                emit either 1 = row [[<th> col-lbl col </th>]] [
                    [
                        <td width="110"> any [
                            get/any mk-var col row - 1 ""
                        ] 
                        </td>
                    ]
                ]
            ]
            emit </tr>
         ]
        emit </table>
        out-buff: replace copy html-template "$table" out-buff
        write %rebolcalc-out.html out-buff browse %rebolcalc-out.html
    ]
]
avg: average: func ["Arithmetitc mean" block [any-block!]] [
    remove-each val block [no-val? val]
    either empty? block [0] [divide  sum block  length? block]
]
gcd: func ["Greatest common denominator" m [integer!] n [integer!]] [
    either (m // n) = 0 [n] [gcd n (m // n)]  ; Euclid's algorithm
]
geo-mean: func ["Geometric mean" block [any-block!]] [
    either empty? block [0] [(product block) ** (1 / length? block)]
]
median: func [
    "Returns the number in the middle of a set of numbers sorted by value"
    block [any-block!] /local len mid
] [
    block: sort copy block
    len: length? block
    mid: to integer! len / 2
    either odd? len [
        pick block add 1 mid
    ][
        (block/:mid) + (pick block add 1 mid) / 2
    ]
]
mode: func [
    "Returns the most frequently occurring value in the block"
    block [any-block!]
    /local last-item result high-count count
][
    block: sort copy block
    result: last-item: first block
    count: high-count: 1
    foreach item next block [
        either item = last-item [count: count + 1] [
            if count > high-count [
                high-count: count
                result: last-item
            ]
            last-item: item
            count: 1
        ]
    ]
    if count > high-count [result: last-item]
    result
]
product: func [
    "Multiplies all the values in the block"
    block [any-block!] /local result
][
    remove-each val block [no-val? val]
    result: 1
    foreach value block [result: result * value]
    result
]
sum: func [
    "Adds all the values in the block"
    block [any-block!] /local result
][
    remove-each val block [no-val? val]
    result: 0
    foreach value block [result: result + value]
    result
]
sum-rows: func [
    "Adds a range of row values"
    row start end
][
    total: 0
    for i start end 1 [
        do rejoin ["total: total + " row i]
    ] 
    total
] 
; =sum-rows "b" 1 4 
sum-cols: func [
    "Adds a range of column values"
    col start end
][
    total: 0
    for i start end 1 [
        do rejoin ["total: total + " i col]
    ] 
    total
]
; =sum-cols 2 #"b" #"e"
col-lbl: func [col] [form to char! 64 + col]
cell-name: func [col row] [join col-lbl col row]
mk-cell-size: func [col] [
    either any [none? col-widths  col > length? col-widths] [cell-size] [
        as-pair col-widths/:col cell-size/y
    ]
]
mk-var: func [col row] [to lit-word! cell-name col row]
sheet: [
    origin 5x5 space 1x1 across
    style cell field cell-size edge none with [formula: none] [
        enter face  compute  face/para/scroll: 0x0
    ]
    style label text cell-size white rebolor bold center
    style menu button 60x20 silver edge [size: 0x0] shadow off with [
        font/colors: [0.0.0 0.0.128]
    ]
    menu "New"  #"^n" [new-sheet]  menu "Open" #"^o" [open-sheet]
    menu "Save" #"^s" [save-sheet] menu "Save As" #"^a" [save-sheet/as]
    menu "HTML" #"^t" [emit-html]
    text 10 "" text "(Press [F2] to edit cell formulas)"
    return
]
repeat row 1 + sheet-size/y [   ; +1 accounts for header row
    repend sheet ['label (as-pair 30 cell-size/y) either 1 = row [
            ""
        ][
            form row - 1
        ]
    ]
    repeat col sheet-size/x [
        append sheet compose/deep either 1 = row [[label (col-lbl col)]] [
            [cell with [var: (mk-var col row - 1)]]
        ]
    ]
    append sheet 'return
]
lay: layout sheet
foreach face lay/pane [
    if 'cell = face/style [
        repend cells [face/var face]
        set face/var none
    ]
]
focus second cells
insert-event-func :event-func
gui: [
    across
    g: box window-size with [pane: lay pane/offset: 0x0]
    scroller as-pair 16 window-size/y [
        g/pane/offset/y: g/size/y - g/pane/size/y * value show g
    ]
    return
    scroller as-pair window-size/x 16 [
        g/pane/offset/x: g/size/x - g/pane/size/x * value show g
    ]
]
view layout gui

Try saving the text below to a text file, then load it as a spreadsheet in Nano-Sheets to see how some useful features are implemented. This is the "native" internal format that Nano-Sheets uses to save data. You can also use the modified version above to save and load flat and blocked tables of REBOL data, as well as standard CSV files that are compatible with traditional spreadsheet applications:

do [
    right-now: does [now/time/precise] 
    circle-area: func [diameter] [diameter / 2 ** 2 * pi]
] 
buttons [
    A10 "Random-test" [
        set-cell 'a11 circle-area random 10 1E-2
    ] 
    C10 "test-2" [set-cell 'c11 right-now] 
    A5 "Check" [print "check"] 
    F16 "Done" [quit]
] 
A1 ["test"] 
C1 [[now/date]] 
D1 [3] 
E1 [$200.00] 
F1 [1x2] 
E2 [[d1 * e1]] 
A11 [19.63] 
C11 [0:46:00.171]
C12 [[c11 + 1]]

As you learn more about REBOL coding, you'll be able to easily modify and extend the capabilities of the Nano-Sheets program in ways that would be very difficult or impossible to accomplish using other spreadsheet applications.

9. Using REBOL to Create Presentations

9.1 REBOL as Presentation Software

REBOL GUI features enable simple methods for laying out images and text with a variety of fonts, styles, colors, gradients, and the ability to create animations, add sounds, and make use of other elements that are useful in creating captivating audio/visual presentations. REBOL's graphic capabilities provide advanced methods for creating images from code, which are difficult to design even with complex graphic manipulation software (a topic for much later in this text). In most simple cases, applications such as PowerPoint and Photoshop can be easily replaced by straightforward REBOL code.

9.2 Some Basic Layout Ideas and a Simple Code Framework for Presentations

Slide show presentations are often shown in full screen mode. In REBOL, the size of the screen is stored in the value "system/view/screen-face/size", so the following code creates a full screen white box that closes the GUI when clicked:

REBOL [title: "Empty White Screen"]
view center-face layout [
    at 0x0 box system/view/screen-face/size white [unview]
]

Here are a couple of GUI layouts that serve as examples of slides with text and images. Clicking anywhere on the screen advances from one slide to the next:

REBOL [title: "Slide 1"]
view center-face layout [
    at 0x0 box system/view/screen-face/size white [unview]
    at 20x20 h1 blue "Slide 1"
    box black 2000x2
    text "This slide takes up the full screen."
    text "Adding images is easy:"
    image logo.gif
    image stop.gif
    image info.gif
    image exclamation.gif
    text "Click anywhere on the screen to close..."
    box black 2000x2
]

REBOL [title: "Slide 2"]
view center-face layout [
    at 0x0 box system/view/screen-face/size effect [
        gradient 1x1 tan brown
    ] [unview]
    at 20x20 h1 blue "Slide 2"
    box black 2000x2
    text "Gradients and color effects are easy in REBOL:"
    box effect [gradient 123.23.56 254.0.12]
    box effect [gradient blue gold/2]
    text "Click anywhere on the screen to close..."
    box black 2000x2
]

REBOL [title: "Slide 3"]
view/options center-face layout [
    at 0x0 box 600x400 [unview]
    at 20x20 
    text "This slide is smaller, and as simple as can be"
    text "Click anywhere on the screen to close..."
] 'no-title

This program uses q-plot to create graph images of monthly sales and expense numbers, and then displays them in a full screen presentation that can be shown to a group:

REBOL []
do %q-plot.r
save/png %sales.png to-image quick-plot [
    600x400
    bars [5 3 8 2 10 3 4 9 5 7]
]
save/png %expenses.png to-image quick-plot [
    600x400
    line [9 2 4 1 7 3 8 14 10 5 6]
]
view center-face layout [
    at 0x0 box system/view/screen-face/size white [unview]
    at 20x20 h1 blue "February Sales:"
    image load %sales.png
]
view center-face layout [
    at 0x0 box system/view/screen-face/size white [unview]
    at 20x20 h1 blue "February Expenses:"
    image load %expenses.png
]

Making a slideshow framework to display consecutive layouts is as simple as creating a block of nested blocks containing the GUI code, and then using a foreach loop to display each layout:

REBOL [title: "Simple Presenter"]
slides: [
    [
        at 0x0 box system/view/screen-face/size white [unview]
        at 20x20 h1 blue "Slide 1"
        box black 2000x2
        text "This slide takes up the full screen."
        text "Adding images is easy:"
        image logo.gif
        image stop.gif
        image info.gif
        image exclamation.gif
        text "Click anywhere on the screen for next slide..."
        box black 2000x2
    ]
    [
        at 0x0 box system/view/screen-face/size effect [
            gradient 1x1 tan brown
        ] [unview]
        at 20x20 h1 blue "Slide 2"
        box black 2000x2
        text "Gradients and color effects are easy in REBOL:"
        box effect [gradient 123.23.56 254.0.12]
        box effect [gradient blue gold/2]
        text "Click anywhere on the screen to close..."
        box black 2000x2
    ]
    [
        at 0x0 box 600x400 [unview]
        at 20x20 
        text "This screen is smaller, and as simple as can be"
        text "Click anywhere on the screen to close..."
    ]
]
foreach slide slides [
    view/options center-face layout slide 'no-title
]

You can simplify coding tediously repetitive layout elements, by only putting unique GUI elements in each slide. Widgets and layout code to appear in all slides can be inserted in a "forever" loop. This example separates out the title, the text background box color/effect, and layout code to appear in each unique slide, and adds forward and back controls, bar lines (black boxes), and colors to appear in every slide. In this example, the "compose" function is used to insert data contained within parentheses. To create your own slides, all you need to do is edit the unique code to appear in each individual slide layout (title string and unique GUI code for each slide):

REBOL [title: "Presenter"]
slides: [
    "Slide 1 - A Few Basics"  
    [
        text "By default these slides are white and full screen."
        text bold "Adding images is easy:"
        image logo.gif
        image stop.gif
        image info.gif
        image exclamation.gif
        text {
            Press the space bar, right arrow key, or left click screen
            for the next slide.  Press the left arrow key, or right
            click screen to go back to previous slide.  Press the 'X'
            key to quit...
        }
    ]
    "Slide 2 - Colors and Gradients" 
    [
        at 0x90 box as-pair system/view/screen-face/size/1 220 effect [
            gradient 1x1 tan brown
        ]
        at 20x70 text "Colors and gradient effects are easy in REBOL:"
        box effect [gradient 123.23.56 254.0.12]
        box effect [gradient blue gold/2]
        text {
            Left arrow key or right click screen to go back, 'X' key to
            Quit...
        }
    ]
    "Slide 3 - A Simple Window"
    [
        text "This slide is as simple as can be."
    ]
    "Slide 4 - Lots of Stylized Text"
    [
        across
        text "Normal"
        text "Bold" bold
        text "Italic" italic
        text "Underline" underline
        text "Bold italic underline" bold italic underline
        text "Serif style text" font-name font-serif
        text "Spaced text" font [space: 5x0]
        return
        h1 "Heading 1"
        h2 "Heading 2"
        h3 "Heading 3"
        h4 "Heading 4"
        tt "Typewriter text"
        code "Code text"
        below
        text "Big" font-size 32
        title "Centered title" 200
        across
        vtext "Normal"
        vtext "Bold" bold
        vtext "Italic" italic
        vtext "Underline" underline
        vtext "Bold italic underline" bold italic underline
        vtext "Serif style text" font-name font-serif
        vtext "Spaced text" font [space: 5x0]
        return
        vh1 "Video Heading 1"
        vh2 "Video Heading 2"
        vh3 "Video Heading 3"
        vh4 "Video Heading 3"
        label "Label"
        below
        vtext "Big" font-size 32
        banner "Banner" 200
    ]
    "Slide 5 - Live Code"
    [
        h3 "Remember, These Slides Are Live, Fully Functional GUIs!"
        box red 500x2
        bar: progress
        slider 200x16 [bar/data: value show bar]
        area "Type here"
        drop-down 200 data reduce [now now - 5 now - 10]
        across 
        toggle "Click" "Here" [alert form value]
        rotary "Click" "Again" "And Again" [alert form value]
        choice "Choose" "Item 1" "Item 2" "Item 3" [alert form value]
        radio radio radio
        led
        arrow
        return
    ]
]
indx: 1
forever [
    slide: compose [
        size system/view/screen-face/size
        backdrop white [
            if indx < ((length? slides) / 2) [indx: indx + 1 unview]
        ] [
            if indx > 1 [indx: indx - 1 unview]
        ]
        at 20x20 h1 blue (pick slides (indx * 2 - 1))
        box black as-pair (system/view/screen-face/size/1 - 40) 2
        (pick slides (indx * 2))
        box black as-pair (system/view/screen-face/size/1 - 40) 2
        key #"x" [quit]
        key #" " [
            if indx < ((length? slides) / 2) [indx: indx + 1 unview]
        ]
        key keycode [right] [
            if indx < ((length? slides) / 2) [indx: indx + 1 unview]
        ]
        key keycode [left] [
            if indx > 1 [indx: indx - 1 unview]
        ]
    ]
    slide: layout slide
    view/options center-face slide 'no-title
]

It's important to realize that because these slides consist of live, running REBOL code, they can contain much more than just static text and images. Any sort of fully functional application of deep complexity can be included. You could, for example, include charts, tables, or even a working spreadsheet that performs live calculations on instantly updated data. Using the few simple tools you've seen so far, you can easily create presentations that are all but impossible using traditional presentation software.

9.3 Using Tab Panels and Menus to Present Information

Though not a traditional slide format, a simple and effective way to present multiple screen layouts is by using a tab panel widget. The following code contains a tab panel, and also a useful menu widget, created by Richard Smolak. The same 5 example slides shown in the previous section are demonstrated here. Menus can be used to pop up small text alerts, requestors, and choices that alter the state of screens in the presentation. Simply copy the compressed tab panel code (and menu code if needed), plus the "insert-event-func" code, then put your slide code inside the "tab-panel data" block. The syntax required to use optional menus should be intuitively understandable by examining the example code provided here. Beyond being a nice way to display pages of presentation data, these two GUI tools are useful for building all types of applications which require significant screen real estate:

REBOL [title: "Tab Panel and Menu Presentation"]

; Tab Panel Widget: 

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}


; Menu Widget:

do load decompress #{
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C2E2C89D79109E0C7621F0406292DD4CEE1A3D6003F1C97B5CD98F4F594ED30C
057166A52319756AA5D4512D414A324A55456745D127EC4CD6A1243CBC050AB3
9D95E4FF4AD3829BC98E32A3F1B43F999448221B97C4C9998D0D54BD6011D5DD
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436CC7E3F624F89732B0E08F6385AB4AFE22F50D69676081642294B44410F994
60414C3DB55993463063A95C406B8AE23BDBF231D90CC756C249A8B261726C60
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F022CA2E9EB03B26E25E49DEE530480A41EDBCB15B1D83CDA3B62FD32519371E
3DE7E6C57724A452D79DE9AC681C28452C32F5E154264A874DE5A2257EADCAB3
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8BB782C12732E21B663C8F5D82914872B36B38325AB011E325D6BFBD0989FF97
78E79FFF0120649CE6573C0000
}

insert-event-func [ 
    either event/type = 'resize [
        mn/size/1: system/view/screen-face/pane/1/size/1 
        my-tabs/size: system/view/screen-face/pane/1/size - 15x30
        show [mn my-tabs]  none
    ] [event]
]

view/options center-face layout  [
    across space 0x0 origin 0x0
    mn: menu with [ 
        size: 470x20 
        data: compose/deep [
            " File " [
                "Open" # "Ctrl+O" [request-file]
                "Save" # "Ctrl+S" [request-file/save]
                bar
                "Exit" [quit]
            ]
            " Options " [
                "Preferences" sub [
                    "Colors" [alert form request-color]
                    "Settings" [request-text/title "Enter new setting:"]
                ]
                "About" [alert "Menu Widget by Cyphre"]
            ]
        ]
    ]
    below
    at 10x25 my-tabs: tab-panel data [
        "1" [
            h1 "Slide 1 - A Few Basics"
            text "By default these slides are white and full screen."
            text bold "Adding images is easy:"
            image logo.gif
            image stop.gif
            image info.gif
            image exclamation.gif
            text {
                Press the space bar, right arrow key, or left click screen
                for the next slide.  Press the left arrow key, or right
                click screen to go back to previous slide.  Press the 'X'
                key to quit...
            }
         ]
        "2" [
            h1 "Slide 2 - Colors and Gradients" 
            at 0x90 box as-pair system/view/screen-face/size/1 220 effect[
                gradient 1x1 tan brown
            ]
            at 20x70 text "Colors and gradient effects are easy in REBOL:"
            box effect [gradient 123.23.56 254.0.12]
            box effect [gradient blue gold/2]
            text {
                Left arrow key or right click screen to go back, 'X' key
                to quit...
            }
        ]
        "3" [
            h1 "Slide 3 - A Simple Window"
            text "This slide is smaller, and as simple as can be."
        ]
        "4" [
            h1 "Slide 4 - Lots of Stylized Text"
            across
            text "Normal"
            text "Bold" bold
            text "Italic" italic
            text "Underline" underline
            text "Bold italic underline" bold italic underline
            text "Serif style text" font-name font-serif
            text "Spaced text" font [space: 5x0]
            return
            h1 "Heading 1"
            h2 "Heading 2"
            h3 "Heading 3"
            h4 "Heading 4"
            tt "Typewriter text"
            code "Code text"
            below
            text "Big" font-size 32
            title "Centered title" 200
            across
            vtext "Normal"
            vtext "Bold" bold
            vtext "Italic" italic
            vtext "Underline" underline
            vtext "Bold italic underline" bold italic underline
            vtext "Serif style text" font-name font-serif
            vtext "Spaced text" font [space: 5x0]
            return
            vh1 "Video Heading 1"
            vh2 "Video Heading 2"
            vh3 "Video Heading 3"
            vh4 "Video Heading 3"
            label "Label"
            below
            vtext "Big" font-size 32
            banner "Banner" 200
        ]
        "5" [
            h1 "Slide 5 - Live Code"
            h3 "Remember, These Slides Are Live, Fully Functional GUIs!"
            box red 500x2
            bar: progress
            slider 200x16 [bar/data: value show bar]
            area "Type here"
            drop-down 200 data reduce [now now - 5 now - 10]
            across 
            toggle "Click" "Here" [alert form value]
            rotary "Click" "Again" "And Again" [alert form value]
            choice "Choose" "Item 1" "Item 2" "Item 3" [alert form value]
            radio radio radio
            led
            arrow
            return
        ]
    ]
] [resize]

9.4 Show.r - A Useful Line-By-Line Presentation System

Carl Sassenrath (the creator of REBOL) released a simple and productive presentation tool at http://www.rebol.com/notes/devcon07-carl.zip. Here's the code (you only need to edit the title and background image - copy and paste the rest):

REBOL [
    Title: "Slideshow Presenter"
    Author: "Carl Sassenrath"
    Version: 3.0.3
]

file:       system/script/args
if not file? file [file: request-file/only]
title-line: "Presentation Title"                               ; EDIT THIS
diags:      %diags.r
save/png %logo.png svv/image-stock/2   ; demo image
back-image: %logo.png                                      ; AND EDIT THIS
author-mode: off
time-need:  1:00

;-- Configuration --------------------------------------------------------

page-size: system/view/screen-face/size
;page-size: 800x600
;page-size: 1024x800
;page-size: 740x480
big-size:  page-size/x > 1000
sect-size: page-size/x / 4 - 40
text-size: (round/to page-size/y / 32 4) - 1 ;pick [28 20] big-size
margin: round page-size/x / 10
h2-size: as-pair page-size/x - margin - 30 text-size * 2
h3-size: h2-size - (text-size / 2)
origin: page-size / 11
def-in: round page-size/x / 7
spacing: page-size / 100x200

;-- Styles ---------------------------------------------------------------

back-image: load back-image

stylize/master [

    vh2: vh2 h2-size left top font [
        size: text-size + 6
        name: "arial black"
        style: [underline]
        color: 240.220.60
        shadow: 3x3
    ]

    vh3: vh2 h3-size left middle font [
        color: white
        style: [bold] ; underline]
        size: text-size
        name: "arial"
    ]
    para [origin: 10x2]
    effect [merge gradmul 96.96.96 128.128.128]

    txt: vtext page-size/x - margin - 50 font [
        style: 'bold
        size: text-size
        shadow: 2x2
    ]

    txtb: txt page-size/x - margin - 50 font [
        color: sky + 30
    ]

    txti: txt italic white effect [merge colorize red]

    code: tt page-size/x - (margin * 2) - 50
        black snow edge [size: 2x2 color: gold]
        ;snow coal edge [size: 2x2 color: gray]
        font [
        size: round (text-size * .8)
        style: 'bold
        colors: [0.0.0 0.0.80]
    ] as-is para [origin: margin: 12x8]
]

bullet: to-image make face [
    size: text-size / 2 - 1 * 1x1
    color: 160.0.0
    edge: make edge [color: black size: 0x0]
    effect: [oval gradmul 1x1 255.255.255 0.0.0 oval]
]
shift-bullet: text-size - bullet/size/y * 0x1

;bold: make face/font [name: "Arial Black" size: 480]
;scale: page-size/x / 800 / 17

backdrop: layout [
    size page-size
    across
    at 0x15 box as-pair page-size/x text-size * 2
        edge [size: 0x2 color: gold] 
        effect [merge grid navy gradmul 200.120.100 128.128.128]
    origin 10x20
    banner font-size text-size + 4 italic title-line white 
    ;font-color silver
    return
]

backdrop/image: back-image
backdrop/effect: [gradmul 1x-1 50.50.90 100.120.140 fit]
backdrop: to-image backdrop

end-mark: make face [
    offset: page-size * 0x1 + 40x-20 size: 140x3 ; -140x80
    effect: [gradient maroon green]
]

pan-mark: make face [
    offset: page-size * 0x1 + 40x-20 size: 140x3
    effect: [gradient maroon purple]
]

;-- Scanner --------------------------------------------------------------


*scanner*: context [

;-- Variables:
text: none
part: none
code: none
title: none
out: [] ; holds output block

;-- Emitters:
emit: func ['word data] [
    if block? word [word: do word]
    if string? data [trim/tail data]
    repend out [word data]
]

emit-section: func [num] [
    emit [to-word join "sect" num] text
    title: true
]

;--- Text Format Language:
rules: [
    [to "^/=start" skip to newline (author-mode: true) | none]
    some parts
]
parts: [
    ;here: (print here)
    newline |

    spaces

    ;--Document sections:
    "===" text-line (emit-section 1) |
    "---" text-line (emit-section 2) |
    "###" to end (emit end none) |

    ;--Special common notations:
    "***" para opt newline (emit bullet3 part) |
    "**" para opt newline (emit bullet2 part) |
    "*" para opt newline (emit bullet1 part) |
    ":" define opt newline (emit define reduce [text part]) |
    "#" para opt newline (emit enum part) |
    "!" para (emit txti part)|
    "[" example (emit code detab code) | ; trim/auto
    ";" thru newline |  ; comment
    ";===" to "===" |

    "==" output (emit output head insert code "  ") |
    "=image" file (emit image text) |
    "=all" (emit all true) |
    "=intro" (emit intro true) |
    "=diagram" some-chars (emit diagram text) |
    "=pad" num (emit pad num-n) |
    "=skip" num (clear back back tail out) num-n [to "===" thru newline] |
    "=" some-chars | ; ignore unknown options


    ;--Defaults:
    para (emit para part) |
    skip
]

space: charset " ^-"
nochar: charset " ^-^/"
chars: complement nochar
spaces: [any space]
some-chars: [some space copy text some chars]
text-line: [copy text thru newline]
;par:       [copy part some chars newline]
para: [copy part some [chars thru newline]]
;example:   [copy code some indented] ; | some newline indented]]
example:   [thru newline copy code to "^/]" skip thru newline]
indented:  [some space chars thru newline]
output:    [
    copy code indented any [
        "==" copy text indented (append code head insert text "  ")
    ]
] ; compensate for ==
define:    [
    copy text to " -" 2 skip any space para
]
file:      [
    spaces copy text some chars thru newline (text: to-file trim text)
]
num:       [
    spaces copy text any chars (num-n: either text [to-integer text][1])
]
num-n: 0

;-- Export function to scan doc. Returns format block.
set 'scan-doc func [str] [
    clear out
    parse/all detab str rules
    copy out
]
]

;-- Load it up -----------------------------------------------------------

doc-text: read file
if find doc-text "=author" [author-mode: on]
doc: scan-doc doc-text
;?? doc halt
;do diags ;;; NASTY!

;-- Globals --------------------------------------------------------------

this-page: doc ; points to current page position
title:   select doc 'title
options: select doc 'options
time-left: 1.0
time-start: now/time
back-flag: false

;-- Helpers -------------------------------------------------------------

title-of: :second
next-page: does [this-page: any [find next this-page 'sect1 this-page]]
back-page: does [
    this-page: any [find/reverse back this-page 'sect1 this-page]
]
limg: :load-image
load-image: func [file][
    either exists? file [
        limg file
    ][
        make image! reduce [page-size / 3 200.0.0]
    ]
]

;-- Page Builder ---------------------------------------------------------

build-page: has [page out emit bull count] [

    at-once: author-mode
    intro: false
    in-sect: false
    count: 0

    ; Slide title line and indentation:
    out: compose [
        across space spacing
        at (origin)
;        vh2 (title-of this-page) return
;        indent margin guide
    ]
    emit: func [blk] [append out compose blk]
    bull: func [depth] [
        emit [pad (20x0 * 2 * depth + shift-bullet)]
        emit [image bullet effect [key 0.0.0]]
        emit [pad (-8x0 - shift-bullet)]
    ]

    foreach [type data] this-page [
        switch type [
            sect1 [
                if in-sect [break]
                in-sect: true
                emit [
                    vh2 (data) return
                    indent (margin) guide
                ]
            ]
            sect2 [emit [pad 0x4 * spacing vh3 (data) return]]
            para [emit [txt (data) return]]
            code [
                emit [
                    pad to-integer margin / 3 code (trim/auto data) return
                ]
            ]
            bullet1 [bull 1 emit [txtb (data) return]]
            bullet2 [bull 2 emit [txtb (data) return]]
            enum [
                emit [
                    txtb (join count: count + 1 [". " data]) return
                ]
            ]
            pad [emit [pad (data * text-size * 0x1)]]
            txti [emit [txti (data) return]]
            define [
                emit [
                    pad 30 txt def-in no-wrap (data/1) txtb (data/2) 
                    return
                ]
            ]
            diagram [
                type: layout/tight blk: get to-word data
                emit [
                    pad (as-pair margin 30)
                    ;panel (type/size) [(blk)]
                    return
                ]
            ]
            image [
                data: load-image data
                emit [
                    pad (
                        as-pair 
                        page-size/x - data/size/x / 2 - margin
                        text-size
                    )
                    image (data)
                    return
                ]
            ]
            intro [
                intro: true
                at-once: true
            ]
            all [at-once: true]
        ]
    ]
    out: layout/tight out
    offs: 100x100
    if intro [
        foreach face out/pane [
            if face/style = 'txt [offs: 110x120]
            face/offset: face/offset + offs
        ]
    ]
    out/pane
]

;-- Show page:
show-page: func [out] [
    ; Do we step through items one at a time?
    either any [at-once back-flag] [
        items: []
    ][
        items: copy next out
        clear next out
    ]
    screen/pane: out
    if at-once [show-end-mark]
    show screen
    back-flag: false
]

pan: []

show-end-mark: does [
    time-used: now/time - time-start
    either time-need - time-used <= 0:00 [
        end-mark/effect/3: red
        end-mark/size/x: 140
    ][
        end-mark/size/x: (
            to-decimal (time-need - time-used) / to-integer (time-need)
        ) * 140
    ]
    append screen/pane end-mark
]

;-- Traverse pages:
next-item: does [

    if not empty? pan [
        append panel pan/1
        remove pan
        if empty? pan [
            append screen/pane pan-mark
        ]
        show screen
        exit
    ]

    either not empty? items [
        if items/1/style = 'panel [
            panel: items/1/pane
            pan: copy panel
            clear panel
            append screen/pane items/1
            remove items
            next-item
            exit
        ]
        if items/1/style = 'image [
            append screen/pane items/1
            remove items
        ]
        append screen/pane items/1
        remove items
        if empty? items [show-end-mark]
        show screen
    ][
        next-page
        show-page build-page
    ]
]

back-item: does [
    pan: []
    back-page
    back-flag: true
    show-page build-page
]

;-- Handle Keystrokes:
do-key: func [key] [
    if key = escape [quit]
    switch key [
        #" " [next-item]
        #"^(back)" [back-item]
        down [next-item]
        up [back-item]
        page-down [next-page show-page build-page]
        page-up [back-item]
    ]
]

count-slides: has [n d] [
    n: 0
    d: doc-text
    while [d: find/tail d "^/==="] [n: n + 1]
    n
]

this-page: doc ;next-page halt

;-- Build screen and event handler:
screen: [
    size page-size
    across
]

if not author-mode [
    append screen [
        at (as-pair page-size/x - 150 20) t1: txt form now/time
        at (origin) guide
        v1: vh2 "Show07.r Information and Setup" return
        vh3 200 "Version:" 
        vh3 gold form system/script/header/version return
        pad 0x30
        vh3 200 "File: " vh3 gold form file return
        vh3 200 "File size:" vh3 gold reform [
            round (511 + size? system/options/script) / 1024 "K"
        ] return
        vh3 200 "Slides: " vh3 gold form count-slides return
        pad 0x30
        vh3 200 "Page size: " vh3 gold form page-size return
        vh3 200 "Font size: " vh3 gold form text-size return
        vh3 200 "Head font: " vh3 gold form v1/font/name return
        vh3 200 "Body font: " vh3 gold form t1/font/name return
        vh3 200 "Origin: "   vh3 gold form (origin) return
        vh3 200 "Margin: "   vh3 gold form margin return
        vh3 200 "Spacing: "   vh3 gold form spacing return
    ]
]

screen: layout/tight screen

screen/image: backdrop
screen/color: navy
view/new screen

insert-event-func func [face event][
    switch event/type [
        key [do-key event/key]
        down [next-item]
        alt-down [back-item]
        close [quit]
    ]
    event
]

items: []
if author-mode [show-page build-page]

do-events

Using the program above is easy. Save it as %show.r. Edit the "title-line" and "back-image" variables. Upon running the program, a file is requested. Save the following text file as show-example.txt, and load it into show.r when requested (you can also examine the text files included in the download at http://www.rebol.com/notes/devcon07-carl.zip - it contains three actual presentations created by Carl). The space bar, mouse, and cursor keys control progress of the slide contents:

===Presentation Title

=intro

    ---Nick Antonaccio

    Operating Manager
    Merchants' Village, LLC
    Pittston, PA  2013

===A Main Slide Header

    ---A Sub Header
    (Some sub text)

=pad
    #Numbered item 1
    #Numbered item 2
    #Numbered item 3
    #Numbered item 4

===Another Main Slide

    ---Another Sub Header

    *Bullet Item 1:
        **Sub Bullet Item 1a
        **Sub Bullet Item 1b
        **Sub Bullet Item 1c
    *Bullet Item 2:
        **Sub Bullet Item 2a
        **Sub Bullet Item 2b
        **Sub Bullet Item 2c
    *Bullet Item 3
    *Bullet Item 4

===A Third Main Slide

    ---Subheader:

=image rebol.gif

=pad

=image info.gif

===Slide 4

    ---Subheader 4:
    Topic 1 - idea 1
    Topic 2 - idea 2
    Topic 3 - idea 3
    Topic 4 - idea 4

[
    A preformatted text block:

        Idea 1:  some thoughts
        Idea 2:  some thoughts
        Idea 3:  some thoughts
        Idea 4:  some thoughts
]

===Slide 5

    Some Text

    ---Definitions:

    :Idea 1 - definition of Idea 1
    :Idea 2 - definition of Idea 2
    :Idea 3 - definition of Idea 3
    :Idea 4 - definition of Idea 4

=all

---Last Idea 1
---Last Idea 2
---Last Idea 3

###

Notes: nothing below the 3 pound characters appears in the presentation.

Because this program is entirely REBOL code, you can make changes and add functionality to it as needed. And just as with all other REBOL software tools, you can transfer, install, and quickly send by email the entire program, together with the REBOL interpreter, even to users with low powered computers and slow bandwidth Internet connections. The program will run on any operating system supported by REBOL, and the entire setup is free for anyone to copy, use, alter, etc.

9.5 Creating "Screen Shot" Images of GUIs

When building presentations, it can be helpful to have screen shots of programs and/or to build graphic layouts using the REBOL graphic dialect. You can use the "to-image" function to create images from GUI layouts, and the "save/png" function to save image data to a .png file:

REBOL [title: "Create Images From GUI Code"]
save/png %image1.png to-image layout [
    size 600x400
    backdrop white
    h1 blue "Slide 1"
    text "Here's a red box:"
    box red "I'm red!"
]
browse %image1.png

Here's an advanced graphic example by John Niclasen (the "draw" dialect used here will be covered in more depth later in this tutorial):

REBOL [title: "Shiny Black Button"]
sz: 200x400
img: make image! sz
img/alpha: 255
draw img compose [
    pen none
    fill-pen linear (as-pair 0 sz/y / 2) -50.5 70.5 90.0 1.0 1.0
            45.45.47 9.9.11 108.113.117
    circle (as-pair sz/x - 115 sz/y / 2) 70.5
    fill-pen 1.0.5
    circle (as-pair sz/x - 115 sz/y / 2) 68.5
    reset-matrix
    fill-pen linear (as-pair sz/x - 115 sz/y / 2) -60.5 30.5 45.0 1.0 1.0
            161.164.169 161.164.169 89.94.100
    box 
        (as-pair sz/x - 115 - 26 sz/y / 2 - 26) 
        (as-pair sz/x - 115 + 26 sz/y / 2 + 26) 10.0
    fill-pen 1.0.5
    box 
        (as-pair sz/x - 115 - 22 sz/y / 2 - 22) 
        (as-pair sz/x - 115 + 22 sz/y / 2 + 22) 6.0
    reset-matrix
    fill-pen linear (as-pair 0 sz/y / 2 - 26) -50.5 100.5 90.0 1.0 1.0
            1.0.5.255 200.214.226.224 200.214.226.128
    shape [
        move 154x200
        arc 16x200 68.0 68.0
        arc 154x200 -149.0 68.0
    ]
]
save/png %black-btn.png to-image layout [
    backdrop 1.0.5
    image img
]
browse %black-btn.png

9.6 Embedding Binary Resources (images, sounds, files etc.) in Code

The following program can be used to encode external files (images, sounds, DLLs, .exe files, etc.) so that they can be included within the text of your program code:

REBOL [Title: "Simple Binary Embedder"]

system/options/binary-base: 64
file: to-file request-file/only
data: read/binary file
editor data

Use "load (data)" to make use of any text data created by the above program. This example uses a text representation of the image at http://musiclessonz.com/test.png, encoded with the program above:

picture: load 64#{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}
view layout [image picture]

The program below allows you to compress and embed files in your code. This compressing BINARY RESOURCE EMBEDDER program will be referred to many times throughout the tutorial. Save it to a .r file so that it can be run later:

REBOL [Title: "Binary Resource Embedder *** SAVE THIS PROGRAM ***"]
system/options/binary-base: 64
editor picture: compress to-string read/binary to-file request-file/only

To use the compressed version of data created by the program above, use the following code:

to-binary decompress {compressed data}

For example:

REBOL []
image-compressed: load to-binary decompress 64#{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}
view layout [image image-compressed]

You will use the binary resource embedder regularly. It's a good idea to save it now to your desktop or some location on your hard drive that's easily accesible.

9.7 Playing Sounds

Playing .wav sound files is easy in REBOL:

insert s: open sound:// load %/c/windows/media/tada.wav wait s close s

Just as with images, you can use the "Binary Resource Embedder" program to save sound files as code in your programs. This example loads and plays an embedded sound:

REBOL []
my-sound: load to-binary decompress 64#{
    eJxtlHtMU1ccx6vGR3kWLMWpm5pskc2pi3MkqFNYJsh0oigV5KEULK2lpdDb9vbe
    9r56W1pogSKltBQqSGGAlYeimAlDkU1H1KgssrhBmFNhjAECHcZl2bVo1LjfyTm/
    nO/vdf45n9joyMjphTTaoQj2Tq4QWB1Io9HmUSt8Fc2z59GWUEp6KpB6k8pC3zJs
    7nzTvXbB/sdhmMdjcx5744q9SkHf1l4f/LLhq+K33jZnOI6/3gZBVAjq8Qj6Mkzl
    ek5KwBEpL11saGyrANhx4kKHzUBgmFKhUKKIAgBAlNRqNaSayiO1pEqeLeTzxZjJ
    nA+KAK2ByBaidle1XoGVnrLjx3kSlULEOSaBIBmkMZkL9Lo8owYUZYqyRLwMMVJo
    NqgkoL7MQoqOiXUVzpPl1a7OiyXS6K2RBxJiE1KgitrTteYyq0ktStgbE3MwTUha
    7BXFmDxHjpGITE5Unu++dLaupc2UFTLfd5PEZi8xObp7W/Ts8N3Jx3npXMjqarQA
    8XFHpJBUeAwscNRZ8wwF1a7auvIzVWRCwCL/XY6B4c5CWGYol+8LWfk52X63t1Ka
    mnw0Izk+XkCcbDpVKueKUdvpRofVfulms3TlIh8mODQ7fjpx2359ERTFZB3u+Gt2
    MH+zr8+mgwJMZ2/vajYeDt2aYr72U7eNUDf+es+yYQFzQcQvs+MTmQH0zaTTsued
    j/HHT2b6vloc6L0+71Z/hw2RykVHvt6bVtTZd+ecraCq3sT28fNnFD4bdQ/sWhwQ
    xHG14HH7iHtPpi6ELgn0CnFNTQybdwSviYLs39TYyqwN565cq+evoQctDvv+6cjT
    ns/ogQGH6r4tVwh0PWMjzq1egb5rqqfHJhq3+Pt9kOW61l2jh3TOG0Pt/BV01sL9
    A+7H/5xi+TGWpl/pq0cScxruP2qI8g70W2Zxj7ovb/cJYCS0D49dMXC5up4H13OC
    vFkLEodnhv8t8WUE+AsHn9w27totPj94XbXCZ6l31uj45MOkJUz65tbJiZGahJ1p
    rv6fcZYXa/7eodlHtLplXqyFkXenJ7qSwz4VNlxuTlrK8NvYNDPqrl9LDcq4Pzk5
    aIyNFpdftITSmfQP256NuH9jL2L6MhVDk2Mdiojt8WBZniB8bWha7f2JOyf2BLO2
    4b1jk301pAxAeFtWegfvbJgan36ofc/Hj7G/cuCPvlaYx04SZPCT4lKExvqLbRXg
    wS+jBZbv+vuuNhWDieuCAoN3EP0zU5PnOcu9vEO41Tdu9zp1AOc4N4PDPpSYlV/T
    dtaBcWJi+YbWH+/e7HAoD6zyZyyP0t9z//1nq2Cjj/8nKaXtP1ytOyHn8TkZ3DRu
    ugjWWU9WFqMivhCznunq6W42Z4Yt8wrYwGt++NR9x5K0/t33I0TFrZ1tTj3ATU7l
    iUFQli2SwFrTiaJ8jdZgrmpou+CqkOz+yD94XZK568Hvt5rwo3u+iEmR6IttZUYS
    yBRkyhFCDcnEmdkArMkvsTlqapx1VeWGnCNRYWHhidKi+pbW+tJ8pVwuQ3G1BoVz
    eOkcbg6caywoyMWVIKTEqf9ozNPrcrUYLMuRABBO6nUkppACAIzpqLQ8LYmpIBAE
    FRAEwbASwQmCwFSwgpIgJarW6inTUfUakiTVOAJTMkJoNCSuAmVSQCqHUdwTec4X
    tRrHVEpYqaKMIg9OqNVqAvcgh9RoczUkgSKeGMUlRKWkBqpQah6Gzkko/oJjOE7g
    L2FFAc2DM8zTjHoZDKsw4vlEDwyRF5xUKZVUj7lagsCxOfYR/wHwfuhW/AUAAA==
}

insert port: open sound:// my-sound wait port close port

9.8 Launching Code in Separate Processes

For background sounds and other elements of a presentation, it can be helpful to run code sections as separate programs which don't block or interfere with the operation of your main program. You can accomplish this easily by writing the separate code to a text file, and then using the "launch" function to run it. The "launch" function opens a new instance of the REBOL interpreter, to run the loaded file. The launched code executes as a totally separate and independent program. Be sure to include a REBOL header in the saved program:

REBOL []

write %playsound.r {
REBOL []
insert s: open sound:// load %/c/windows/media/tada.wav wait s close s
}

launch %playsound.r

9.9 Running Command Line Applications

The "call" function executes commands in your computer's operating system (i.e., DOS and Unix commands). This can be really useful when creating presentations of all kinds. The example below opens Windows' Notepad to edit the "C:\YOURNAME.txt" text file created earlier (leaving out the /show option runs the program in a hidden window):

call/show "notepad.exe c:\YOURNAME.txt"

This next example opens Windows' Paint program to edit an image we downloaded earlier in the tutorial:

call/show "mspaint.exe c:\bay.jpg"

Here's an example that embeds an executable program into the code, decompresses, and writes the program to the hard drive, and then runs it with the call function:

program: load to-binary decompress 64#{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}
write/binary %program.exe program
call/show %program.exe

The "call" function has many options that allow you to monitor, control, and make use of output from external command line applications. Type "help call" into the REBOL interpreter for an introduction. For more information, see http://rebol.com/docs/shell.html.

9.10 Creating Simple Animations

You can place your widgets at specified coordinate positions (XxY coordinates indicate X pixels over and Y pixels down):

REBOL []
view layout [
    size 600x400
    at 200x250 btn "button 1"
    at 300x350 btn "button 2"
]

Change a labeled widget's position using the "/offset" refinement, followed by a colon:

REBOL []
view layout [
    size 600x400
    at 20x20 btn1: btn "button 1" 
    at 100x20 btn "change button 1's position" [
        btn1/offset: 300x250
        show btn1
    ]
]

You can create a coordinate position from two separate numbers, using the "as-pair" function (paste/F5):

REBOL []
x-size: 600
y-size: 400
x-position: 20
y-position: 20
view layout [
    size (as-pair x-size y-size)
    at (as-pair x-position y-position) button1: btn "button 1"
]

To create a repeating loop, just copy the line below that starts with the word "box", and the closing 3 square brackets, into your GUI code. Anything inside those brackets will be repeated continuously. This is a simple way to create continuous motion:

REBOL []
view layout [
    size 600x440
    btn1: btn red
    box 0x0 rate 0 feel [engage: func [f a e] [if a = 'time [
        btn1/offset: btn1/offset + 2x2
        show btn1
    ]]]
]

To control movement using keyboard controls, you need to check for user keystrokes:

REBOL []
view center-face layout [
    size 600x440 
    text "Press an arrow key"
    key keycode [left]  [alert "You pressed the LEFT arrow key"]
    key keycode [right] [alert "You pressed the RIGHT arrow key"]
]

Put the motions to be performed inside square brackets following an if test:

REBOL []
direction: "down"
view layout [
    size 600x440
    btn1: btn red
    box 0x0 rate 0 feel [engage: func [f a e] [if a = 'time [
        if btn1/offset/2 > 420  [direction: "up"]
        if btn1/offset/2 < 1    [direction: "down"]
        if direction = "down"   [btn1/offset: btn1/offset + 0x5]
        if direction = "up"     [btn1/offset: btn1/offset - 0x5]
        show btn1
    ]]]
]

Use REBOL's "within?" function to test for graphic collisions (i.e., when graphics touch, or share coordinate locations):

REBOL []
direction: "down"
view layout [
    size 600x440
    btn1: btn red
    at 20x350 btn2: btn green
    box 0x0 rate 0 feel [engage: func [f a e] [if a = 'time [
        if btn1/offset/2 > 420  [direction: "up"]
        if btn1/offset/2 < 1    [direction: "down"]
        if direction = "down"   [btn1/offset: btn1/offset + 0x5]
        if direction = "up"     [btn1/offset: btn1/offset - 0x5]
        show btn1
        if (within? btn1/offset btn2/offset 1x1) [alert "Collision!"]
    ]]]
]

This simple program demonstrates the some of most important animation techniques discussed here. Catch the falling pieces:

REBOL [title: "Catch"]    
alert "Arrow keys move left/right, up goes faster, down goes slower"
random/seed now/time   
speed: 11   score: 0
view center-face layout [
    size 600x440   backdrop white   across
    at 270x0 text "Score:"  t: text bold 100 (form score)
    at 280x20  y: btn 50x20 orange
    at 280x420 z: btn 50x20 blue
    key keycode [left]   [z/offset: z/offset - 10x0  show z]
    key keycode [right]  [z/offset: z/offset + 10x0  show z]
    key keycode [up]     [speed: speed + 1]
    key keycode [down]   [if speed > 1 [speed: speed - 1]]
    box 0x0 rate 0 feel [engage: func [f a e] [if a = 'time [
        y/offset: y/offset + (as-pair 0 speed)  show y
        if y/offset/2 > 440 [
            y/offset: as-pair (random 550) 20   show y
            score: score - 1
        ]
        if within? z/offset (y/offset - 50x0) 100x20 [
            y/offset: as-pair (random 550) 20   show y
            score: score + 1
        ]
        t/text: (form score)  show t
    ]]]
]

Your ability to create interesting animations is limited only by creative application of movement.

9.11 A Simple Animation Framework for Presentations

A simple animation framework, specifically designed to make easy work of moving and resizing GUI elements in presentations, created by Jeff Kreis, is available at http://www.cs.unm.edu/~whip/presentation.r (be sure to download the demo file at http://www.cs.unm.edu/~whip/test-prez.r). A short discussion of this tool is available on the REBOL mailing list at http://www.rebol.org/ml-display-thread.r?m=rmlBYZS

9.12 Using Animated GIF Images

Another easy way to work with animations in REBOL is with the "anim" style in GUIs. Anim takes a series of still image frames, and plays them in order as an animation with a given rate. The basic format is:

view layout [
    speed: 10
    anim rate (speed) [%image1.gif %image2.gif etc...]
]

The following script will convert an animated .gif into a folder filled with individual frame images:

REBOL []

gif-anim: load to-file request-file
make-dir %./frames/
count: 1

for count 1 length? gif-anim 1 [
    save/png rejoin [
        %./frames/ "your_file_name-" count ".png"
    ] pick gif-anim count
]

This next script will convert a directory of images (such as above, or any other series of images) into an embeddable block of REBOL code. It looks for all the images named [%your_file_name-1.* your_file_name-2.* etc...]:

REBOL []

system/options/binary-base: 64    
file-list: read  %./frames/
anim-frames-block: copy []
foreach file file-list [

    ; Unique portion of file names for your image frames go here.
    ; Leave out this check if you instead want to convert all
    ; files in the directory:

    if find to-string file "your_file_name-" [ 
        print file
        uncompressed: read/binary file
        compressed: compress to-string uncompressed
        append anim-frames-block compressed
    ]
]

editor anim-frames-block

Here's some sample output:

anim-frames-block: [64#{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} 64#{
eJxz93SzsEwMZwhn+M4AAg1g3ACmGsCsBjDnPxj/B1P/waz/YM4oGAXDBij+ZAHT
OiAClCfYOf4zMHLIeGxYcLCZQ1gr5sSGhYfbBZS95nhsXHS0W8I4686JjYuP9ys4
d8l4blpycrJG8KqYk5uWnp5ukHxqjufmZWdnW6hqBUwQfnxuvkPltxaJLSsuLOTt
ZWPdIPzSaal3vZUth6nWhZUsq7NsrUqzQ9f47K17qyWmdW1T2txFsreLdW/Pydu6
rXe2mHrsYuf3j86uLn95Z1/Qf6ZnWeUGD2e38V/3WVOh9viYkfzh3Fvmb1Iap+oq
P7OUKH64ocH2tsisGfkvTy7nXi6nG/n11dGZzLv3RQt8On3c19zY7e8stbyDCxtf
h0rLZBZuKjyYFrv6jsLdZ8xr99lGi3wueRLuGN6+zqSq7MW1700y/hHle4o/PhP8
5Xt+397f3z88Pj3ff/++v79/vGdnYbAGAJfEqNM/BAAA
} 64#{
eJxz93SzsEwMZwhn+M4AAg1g3ACmGsCsBjDnPxj/B1P/waz/YM4oGAXDBij+ZAHT
OiAClCfYOf4zMHLIeGxYcLCZQ1gr5sSGhYfbBZS95nhsXHS0W8I4686JjYuP9ys4
d8l4blri2cIVNC+GU2Hp6elcEX0tnsbLfPpNs++9mTE57fRcyepfJZxfFgUsdNWU
s51l8ihoma+8XatU6cOQVaHCca6zQh+GrYvlrWOVnvbgxrzUo/POzrz2JmpuLuu+
VuntT+9ML316T3VWuf79HXX/t/GuKTJIPBj5UW7bzB0fko75frwVGzP1ffIRa934
tpiQp88O9Zq3q84pL3qwq593uZ621dus61NCJ097K/714b7l3tf1bAv03jfNmv/v
264t3wu2Hn0r9973y6uiy2aql235hJeef35hovexONmK8jc3rzapXLeL03r+6cXl
1fHn9+39/f3D49Pz/ffv+/v7x+fX98/v3////1NWFgZrALxatNdHBAAA
} 64#{
eJxz93SzsEwMZwhn+M4AAg1g3ACmGsCsBjDnPxj/B1P/waz/YM4oGAXDBij+ZAHT
OiAClCfYOf4zMHLIeGxYcLCZQ1gr5sSGhYfbBZS95nhsXHS0W8I4686JjYuP9ys4
d8l4blpycrJG8KqYk5uWnp5ukHxKZMWCZWdnSuW+urOSId11nkP+rx6JLS8C2l0n
y6XO2PLyUovvXDtTCdNXV5pCl8YtnRn68tq6qOVNX6tKdW4uT+ud5sv9RTt6Xt79
Vz3a4Stu7Cq7+OitZ/i7i3tza5n4tCo+3JzWdniTz5oI1cfHNOVXt2pWqp87VaPv
LZf1413C3s7pdmKys0rSL88PZGbbe+vzva1rY3+/PV32+sCubRtnnd0rkJdwj/0h
0wyemh2p644UC7fl7H778NGh3vO6fKbGX1/f2Jx9/9ze3d/fPzjczSvvv2/Pz88v
Lq+Oj7dTYLAGANdbpyswBAAA
} 64#{
eJxz93SzsEwMZwhn+M4AAg1g3ACmGsCsBjDnPxj/B1P/waz/YM4oGAXDBij+ZAHT
OiAClCfYOf4zMHLIeGxYcLCZQ1gr5sSGhYfbBZS95nhsXHS0W8I4686JjYuP9ys4
d8l4blpycrJG8KqYk5uWnp5ukHxqjufmZWdnWxS/unNy8/Lz8x2auWR/BTVeXOwi
Khe7y2Sl47KAiVamXApZV5b4rnWSXbVVO3RB3OF/PN7X1G9usjnfdXdl2dpz2/IK
D339VZZ3fVfZ2kdnd5uqx++t+/9tqvaMlWfXh3IrT7sZ/jHxaHim0zWtSqOnM6a9
FDtbU26cfkDPvrlNc1dm6kVTb22Lv5alaYfm5C+qu3OrNPfa+tzj13Ijv+XemZzI
zv9n+oq7Kye6f9+js2Fz5IFZx4PK+MR+JSy/sTn7/rm9u7+/f3C4m/m7pACDNQAX
yZ/iJgQAAA==
} 64#{
eJxz93SzsEwMZwhn+M4AAg1g3ACmGsCsBjDnPxj/B1P/waz/YM4oGAXDBij+ZAHT
OiAClCfYOf4zMHLIeGxYcLCZQ1gr5sSGhYfbBZS95nhsXHS0W8I4686JjYuP9ys4
d8l4blpycrJG8KqYk5uWendyiezhkdy8zHemsfm9O5LG6m7zHGqjWKRCMo7MY+h4
Z/IrYGXwMp65dq2rAl6FrGJbG3fUKuB12DrPvVqs2gFvwlelHZ/ku3qadvSilMP7
9kqW653fWvay6ezq67rxS6r/P1qjPWPDg4Nu/N+/rvyh9/iYt7zzNs0So6enpi2M
cuuRNLp3qJH/d6hNlEnY+eXS09l6w0qzLq+PPP7s98yy3N2Fp5+dvTtVN78lqf77
u5XTi3wfHpYVj5lTnX3xfsHkeDe98qrS11catc/PK7D+/u74fnNpHv19e35+fnF5
dfz5fXt/f//w+PR8//37/v5mYGJisAYARqapGj4EAAA=
} 64#{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} 64#{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} 64#{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} 64#{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} 64#{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} 64#{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}]

And here's an example of how to write the files in that block back to the hard drive and display them in a GUI:

; Write files:

count: 1
make-dir %./frames/
for count 1 length? anim-frames-block 1 [
    write/binary rejoin [
        %./frames/ "frame-" count ".gif"
    ] to-binary decompress pick anim-frames-block count
]

; Create file list, with frames in numerical order:

file-list: read %./frames/
animation-frames: copy []
for count 1 length? file-list 1 [
    append animation-frames rejoin [
        %./frames/ "frame-" count ".gif"
    ]
]

; Display that file list as an animation:

view layout [
    anim: anim rate 10 frames animation-frames
]

Here's an example that combines the above animated GIF files with normal GUI animation (/offset values adjusted using "for" loops):

view center-face layout [
    size 625x415
    backcolor black
    anim: anim rate 10 frames load animation-frames
    btn "Run Animation" [
        for counter 0 31 1 [
            anim/offset: anim/offset + (as-pair counter 0)
            show anim wait .05
        ]
        for counter 0 24 1 [
            anim/offset: anim/offset + (as-pair 0 counter) 
            show anim wait .05
        ]
        for counter 0 31 1 [
            anim/offset: anim/offset + (as-pair (negate counter) 0)
            show anim wait .05
        ]
        for counter 0 24 1 [
            anim/offset: anim/offset + (as-pair 0 (negate counter))
            show anim wait .05
        ]
    ]
]

9.13 And That's Just the Beginning

As you learn more about general REBOL coding throughout this text and beyond, you'll improve your ability to design GUI screens that exactly match your creative vision. If you want to create more complex visual layouts, GUI and graphic programming should be the focus of your study. For now, understanding the basic framework and concept of switching between slides, adding graphics, text, animation, sound, etc., along with specific pre-made tools like Carl's show.r script, are more than enough to put together effective presentations.

Other tools such as the REBOL Flash .swf creator, covered later in this tutorial, provide additional powerful capability for building and distributing presentations.

10. Makedoc And Other Useful REBOL Productivity Tools

10.1 Makedoc.r - HTML Document Builder

The show.r presentation script demonstrated earlier is really just a variation of another useful REBOL script called "Makedoc". Makedoc is used to create HTML (web) pages quickly and easily using a simple text markup format. Using minimal character patterns, Makedoc allows users to layout headers, subheaders, numbered lists, images, and other common page elements. Makedoc also automatically generates a hyperlinked table of contents for all topics and subtopics. Here's a short sample of the syntax:


Page Title

    By:  Author Name
    Some descriptive info about the page.

===Main Section Header

Main section text.


---Sub Header

Sub section text.

# Automatically numbered item 1

# Automatically numbered item 2

# Automatically numbered item 3

Here's how to include an image:

=image %image.png

Save the text above as a file named example.txt, then download and run the makedoc.r script from http://www.rebol.org/library/scripts/makedoc2.r. When prompted, select the example.txt file, and Makedoc will convert it into a nicely formatted HTML page.

This entire tutorial is actually written in Makedoc format. The source text is available at http://www.re-bol.com/business_programming.txt.

More information and instructions about how to use Makedoc are available at http://www.rebol.net/docs/makedoc.html.

Makedoc has been integrated into the Sitebuilder CGI script, so you can create and edit pages on a web site using only a browser, with simple Makedoc syntax. Much more about creating and using web site CGI programs will be covered in depth in later sections of this tutorial.

10.2 An Improved Text Editor

The text "editor" function built into REBOL is very simple. It doesn't even enable undo/redo for when typing mistakes occur. The following version allows for several such useful features. After running the code below, just use the "editor" function is the normal way, and the new features will be added. Notice that the download procedure is wrapped in a block executed by the "attempt" function, just in case an Internet connection is not available:

if not exists? %e [
    attempt [
        write %e read http://re-bol.com/e
        do e%
    ]
]

; editor none

Here's the program in compressed format, for use in situations where an Internet connection is not available. This script uses Romano Paolo Tenca's undo/redo code to add [ctrl]-z and [ctrl]-y features:

REBOL [Title: "Advanced Editor"]
do undo: decompress #{
789CAD58DD6EA33A10BEA64F61F55C546A85C856DA1BBAE7F441908FE4829358
4B2002A709FBF4677E6C6C2034ED9E8DD406EC99F137BF9E49D936565FAC7833
4DC5FF8ABBE4D4546D7A50975C7CDB6C3642BC88A66DB4F85B9C9ADA1C8CD595
7044AAAA72B13D35A528B6AAD412B913B315AAAE45611A818BE20149418415DB
5AED525C7BE59DBDA9B44496C434BDEEAC286BAD3ADACB8849C1527B1C788580
02447D7915A5EAB425467798C72CC6871FA2D6CDCEEE5FC55EAB2A0805909D3E
B4EF7ABE8EE2C6B75C5865EAB00B9B40209DDE3B6D977A8F2073964C1881CC74
BD9D08A2E7DA343AAD4D0F14685D5876A8169495E9ECF00A80BA932608CE5804
F0A71E0EEA48E7FF75FFEFAF7BE138E165B8179DF62F27DE49C15824E365DB76
42F7E55DD26B2B1EF6A636BBBDC56DA7973B5D646D530FC0422BDAD8BD06BEC3
1110455E293032901FDFD8A37B78E7B5DEAACEDB64649992E8A68A0DEE086414
4C183E88448C5105E025593F83A77C1627E4ABBB040DEA1DA5DF7503E164BB5A
1C6B659AA946B899F57BB3056554338862865F2CF421F74A39551D243AB74F04
9790665D5B47A7B36A93631D07F143B2CD01CC6C3C339E4313D44E87384245A5
6BAB4456B7A502046D2FECE1887FCFE42D78C845BBDD422CA4B64D1942C4F784
2CEE10246052A6F0A988C25648602B981AE9B241FCF80765C243010BB260FC0C
9F22525786559DC523BB5195D6B46844A711A481C08C1A447F5647E6F31A8AA3
DAE9F474E4EFAA3D7304A5BDF9A57D608F0B39C7103E8AD43B91A3ACDA69513C
8BC7F04A64B2D8A0DB0141EEFC098FECDE6BF52E00CCE964B67D48A5A88A70F6
2BB0FFF8943B5BCEA3ACEBDAEE152AC48065375448594C934A16CAAE1453E912
0E374CB36D193155297ADDC01E59380F8BA47FE6942DF70A20A023482D6F3ABC
5360B1C79870856BA4192F113A8C56982445618C808D99C8820CDCEB5A97D657
3DF892A14E9CDBAE8A0038AF8395391D58DCE868F02E078CFF7E149B4BFA4D8E
AC18283799918979E0B672E058B55A634E5345E7902DDE54F9334590DE37B810
12173E1DE6F394A901774C987061C204811D73F8609F009F68C86C94070BC6B0
BA64F59C93133CCE70E3490F21A25E1CC67119D3230973ECDB835E155EBCE91D
D49614614DCCA0B1775939A180CDAB4CE4128A3576DA95804CE836E0C704AAA1
B61002E4685DA5FE2643D48031EA4B92D9D5E26F002F89D33E2677F77F76C462
EFD23B848C2B668E56FA1626A20B699C704A2457FB87711374F943AAA3A53FA3
FA4241B188EE58ADCFAB02A7E8518F2B7517849DBA6654E5666576747CC984D4
A70ABC2EC3AAB737688D8B6D5B9E7A566D6B74CD0695DE321763277A5D31FBA2
0636FA8CA11B690C3D115F7245D4B951AB169D862D91A30A8F2470DEB300EDC9
DDB6EBD1403226FE8F36D7C3E323C71D550F4C37CEBD217AD948AF1EEA6F4D3F
6D500C76545C6A737C6B5557E55916E1A37924A54AB28E6F19D68B7273DB1210
3C936CFC20BEA63936F6C39DE6C01B2B0C1DE757A34E73AC2151297A9E35ACAE
25A5FA130571B112D59F4EA90F732A61A808C763FC3F5903F68A0CFC024934F6
1C91955746552EE761381C6B0787CE5746D464325652A98E67BC519D9D8E134A
46D8718CBB0D99CBF0127274F8EFA1BF81CECF95AB08613E5B4407C5D008319A
FBA360F9EA0F09B35F0F6410D3DBCE343B671C8453C496087D37CE945FBC24FE
D44540FFA56B775D478BF43006E08443F2D9C26BC8D898EF469F1FB3C5B43A5F
A6A171AC976C8DAC82AE2E32228D1EF78FF7E30F29530761C71B1B03400BF709
CDCDCAB418113EBB4107EAA7CAFA123A853AECFB1000BA0C7FD2D9F0F8488F92
47DB9831BBE49E2015C423AFCB1A82AC614DD6907B02963544B2B88CE5938980
DAB3F830A221ACDF3F84FA144853F15D5E138220B913FF08E7532077030A4555
BF6FCF3E7769C49602AF8D7E80CBF79061648807B85DB7B858DA0BDFC7B4F21F
C9601ECC1F140000
}
base-color: 230.230.255  base-effect: []
ctx-edit: mold :ctx-edit
changes: [
    {style tx vtext bold 40x22 font [colors: [0.0.0 200.200.200]]} 
    {style tx text 40x22 font [colors: [0.0.0 170.170.170]]}
    {vtext} {text}
    {btn-enter} {btn} {btn-cancel} {btn} {btn green} {btn} {btn red + 50}
    {btn}
    {[tabs: 28 origin: 4x4]}
    {[tabs: 28 origin: 4x4] with [
            undo: []
            colors: [254.254.254 255.255.255]
        ]}
    {Ctrl-V - paste text}
    {Ctrl-V - paste text^/^-^-Ctrl-Z - undo^/^-^-Ctrl-Y - redo}
]
foreach [original changed] changes [replace/all ctx-edit original changed]
ctx-edit: do ctx-edit

Writing/editing code is the core activity engaged in by programmers, so being able to edit directly with the REBOL interpreter is an essentially useful capability. One benefit of using the simple built in editor is that it operates on any platform supported by REBOL. It works the same way on Windows, Mac, Unix, or other operating systems which may be unfamiliar. The ability to edit scripts provides an instant environment for developing portable software on any OS. The tiny REBOL interpreter is all you need. Metapad (http://liquidninja.com/metapad/download.html) is a great third party editor that can be used for REBOL coding on Windows. Click Options -> Settings -> Primary External Viewer, and set your REBOL path (usually C:\Program Files\rebol\view\rebol.exe).

10.3 GUI Builders and Learning Tools

A primary difference between REBOL and other programming tools is that REBOL tends to require fewer lines of code to accomplish equivalent goals. The GUI dialect is particularly concise compared to other solutions. Typing "view layout [button]" does what requires a page or more of code in other environments. REBOL also has built-in help available for all language constructs. You can search for forgotten functions, look up the syntax of any function or list the content of any object using the "help" function, list all available words using the "what" function, quickly test short bits of code in the console and the text editor, and use the console's auto-complete feature to remember spellings and speed typing. Much more about these and other work enhancing features will be covered later in this tutorial.

As a result of the inherently simple workflow, most REBOL developers tend to write code using a plain text editor, instead of a bloated integrated development environment ("IDE"). It's generally faster and more effective to keep a copy of the REBOL interpreter open, and simply write REBOL code, than it is to use heavy third party GUI builders to layout interfaces, or to rely on complex IDE features to help remember and manage large APIs. One of the pleasant advantages of REBOL is that it's tiny and instantly installed on any computer. No other tools are required to develop or to distribute REBOL software.

Nevertheless, it can be helpful to have a few extraneous tools to help learn and explore the language, and to create simple visual layouts without writing code. The following examples are not industry strength applications, but may be useful for quick design and instruction, to speed presentation layout, etc.:

http://www.rebol.org/view-script.r?script=vid-build.r

http://www.rebol.org/library/scripts/layout-1.8.r

http://www.rebol.org/view-script.r?script=rebolide.r

11. Real World Concerns and Examples: Why "Programming" > Office Software

The programs in this section demonstrate practical, real world examples of how critical company specific features were added to different types of simple applications for managing inventory, payroll, and rent collections.

You've already seen that by creating GUIs, you can make input forms which enable easy input, create custom output displays, and more. Adding extended functionality such as emailing data files to others and sending data to a web server, for example, require simple one-line scripts in REBOL code. You can also create web and network applications that allow users to access data from any location, and from virtually any web connected device. A programmer's potential ability to simply save data to a web server, for example, alone adds a truly dynamic scope of power and usability beyond what's possible with office apps. With REBOL, web and mobile programming requires very little additional learning overhead and provides a wide range of capabilities that aren't so easily acquired using other tools.

But that's just the beginning. Another of the great benefits of custom built applications over spreadsheets, for example, is that they allow perfect control over data entry and display. It's easy to check data for errors using simple form validation code, before incorrect data is permanently saved, and only essential categories of values need to be displayed. You can also easily make automated backups of data, so that information is never accidently overwritten or permanently erased. You can ensure that protected fields of data are never touched during data entry, but only viewable and editable when needed. You can choose that user interfaces are cleanly laid out and labeled exactly as you see fit, and insist upon the workflow order in which data is entered. Collections of small data entry routines, reports and other elements of daily work can be collected and run from a core GUI app, data can be saved, read, and shared between each component, and other features automated behind the scenes so that users see and interact with data exactly as needed. Your ability to use code to speed use, reduce error, and perform calculations and manipulations to data are limited entirely to your own interests, abilities, and priorities. Your palette of fine data management controls and powerful tools will continue to grow as you learn more, and the potential features you can enable are limited only by your own experience, insight, and creative effort.

11.1 An Expanded Inventory Program

You've already witnessed how simple it is to create the example inventory program earlier in this tutorial:

REBOL [title: "Inventory"]
view layout [
    text "SKU:"
    f1: field
    text "Cost:"
    f2: field "1.00"
    text "Quantity:"
    f3: field
    across
    btn "Save" [
        write/append %inventory.txt rejoin [
            mold f1/text " " mold f2/text " " mold f3/text newline
        ]
        alert "Saved"
    ]
    btn "View Data" [editor %inventory.txt]
]

That application creates a data file which can be easily opened as a spreadsheet in Excel, viewed as text in Word, imported into an Access database, etc. In fact, that program and others so far in this text allow users to accomplish many of the same goals as typical office software. You can get columns of data entered by users, display tables in a visual grid, sort and perform calculations on columns/rows, create charts from the values, (and you can engineer other complex functions as needed), etc. Developing even the simplest custom GUI apps, however, enables greatly increased control over data management.

Below is an enhanced inventory program which implements a variety of specifically useful features for the environment in which it was used, as well as additional general security features, control over data entry, etc. Read the comments to see all the specialized features that were added:

REBOL [title: "Real World Inventory"]

; The script allows for manual editing of data using the "editor"
; function.  The improved editor, from the previous section of this
; tutorial, is added here to enable undo/redo for when typing mistakes
; occur:

if not exists? %e [
    attempt [
        write %e read http://re-bol.com/e
        do e%
    ]
]

; This is stock code that removes the word "REBOL" from the GUI header
; bar in Windows.  This makes the program look more professional.  You
; can copy and use these five lines in any program:

tt: "Real World Inventory"
user32.dll: load/library %user32.dll
gf: make routine![return:[int]]user32.dll"GetFocus"
sc: make routine![hw[int]a[string!]return:[int]]user32.dll"SetWindowTextA"
so: :show show: func[face][so[face]hw: gf sc hw tt]

; We can choose to automatically create and save to any desired file name
; in any location:

make-dir %/c/merchants-inventory/
datafile: %/c/merchants-inventory/merchants_mv_inventory.csv
write/append datafile ""
prcnt: 1.0
scanmode: false
roundmode: false

; This backup routine is used to automatically save incremental versions
; of the inventory file, so that no changes are ever lost:

backup-data3: func [msg] [
    write (
        to-file bak-file: replace form datafile "_mv_inventory" rejoin [
            "_mv_inventory-backup--"
            now/date "_"
            replace/all form now/time ":" "-"
        ]
    ) read datafile
    if msg = "msg" [alert (join "Data has been backed up to " bak-file)]
]

; These routines check that appropriate values are entered into the cost
; and quantity fields:

check-errors-f2: does [
    if (
        (f2/text = "0.0") or (f2/text = "") or
        (error? try [to-decimal f2/text])
    ) [
        alert {
            *** ERROR: Enter a decimal in cost field 
            (set mode to 'key' if using keyboard).
        }
        focus f2 show f2
        return 0
    ]
    return 1
]
check-errors-f3: does [
    if ((f3/text = "") or (error? try [to-integer f3/text])) [
        alert "*** ERROR: Enter an integer in quantity field." 
        focus f3 show f3
        return 0
    ]
    return 1
]

; This routine saves the data, and automatically performs a backup.
; Along the way, a common default value is reset in the cost field,
; and the user is notified that the process was successful:

enter-item: does [
    if check-errors-f2 = 0 [return]
    if check-errors-f3 = 0 [return]
    backup-data3 ""
    write/append datafile rejoin [
        mold f1/text " | "  mold f2/text " | "  
        mold f3/text " | "  mold f4/text " | " 
        mold {} " | " mold {} " | " mold {} newline
    ]
    request/timeout/ok "Done" 00:00:01
    set-face f1 ""
    set-face f2 ".99"
    set-face f3 ""
    set-face f4 ""    
    focus f1
]

; This routine allows the user to manually edit the data file, if desired.
; A backup is made first, just to be safe. Along the way a total inventory
; sum is calculated and displayed, and the data file is checked for
; integrity:

view-data: does [
    backup-data3 ""
    total: 0
    inv: read/lines datafile
    if error? try [
        foreach line inv [
            ln: parse line "|"
            line-total: (to-decimal ln/3) * (to-decimal ln/2)
            total: total + line-total
        ]
        alert join "Total Inventory: $" total 
    ][
        alert {
            *** ERROR: Improperly formed data in database.  
            Check each line.
        }
    ]
    editor datafile
]

; The program provides an option to automatically compute a standard
; margin markup, to figure the wholesale cost of any entered item, based
; upon the scanned retail cost.  These functions enable those
; computations, with appropriate data validation error checks along the
; way:

calc-percent: does [
    if error? try [
        if scanmode [f2/text: calculate-barcode-price f2/text show f2]
        f2/text: form (prcnt * (to-decimal f2/text))
        if roundmode [f2/text: form (round/to (to-decimal f2/text) .01)]
        show f2
    ] [alert "*** ERROR: Enter a decimal in cost field."]
]
set-percent: does [
    if error? try [
        prcnt: to-decimal request-text/title/default
            "Default Percent:" form prcnt
    ] [alert "*** ERROR: Enter a decimal."]
]

; The program allows for prices to either be entered by hand, or to be
; extracted from a specialized bar code format that can be entered by a
; USB scanner.  This allows the user to switch entry modes:

scan-mode: does [
    scanmode: not scanmode
    either scanmode [
        b2/text: "Mode: Scan"
    ] [
        b2/text: "Mode: Key"
    ]
    show b2
]

; This routine allows the user to switch between automatically rounding
; computed wholesale values above, or using exact fractional values:

round-mode: does [
    roundmode: not roundmode
    either roundmode [
        b1/text: "Round: On"
    ] [
        b1/text: "Round: Off"
    ]
    show b1
]

; This routine parses values from the specially encoded barcode price
; data entered with a scanner.  This bar code format is unique to the
; business is which this particular inventory is found (i.e., it could
; not simply be entered into or used directly by a spreadsheet - the
; price data needs to be extracted using a parse computation):

calculate-barcode-price: does [
    scanned-price: to-integer (trim/all copy (at copy f2/text 8))
    final-price: rejoin [
        to-string to-integer (
             (scanned-price - (scanned-price // 100)) / 100
        )
        "."
        either (scanned-price // 100) < 10 [
            rejoin ["0" scanned-price // 100]
        ] [
            scanned-price // 100
        ]
    ]
    final-price
]

; Here's the program's GUI window:

view/options center-face layout [
    size 240x400

    ; Users can select from specialized item categories found in this
    ; business, using a quick list choise:

    text "Item:" [
        picked-item: request-list "Items" [
            "1 - Food" "2 - CVS" "3 - Bread" "4 - Electronics" "5 - Coke"
            "6 - Drinks" "7 - " "8 - " "9 - " "10 - "
        ]
        f1/text: copy at picked-item (
            (index? find/only picked-item " - ") + 3
        )
        show f1
    ]

    ; All the special routines created earlier are executed by entering
    ; data into fields, clicking buttons, and otherwise interacting with
    ; simple widgets:

    f1: field "Food"
    text "Cost"
    f2: field ".99" [calc-percent check-errors-f2]
    across 
    btn "%" #"^x" [set-percent]
    b1: btn "Round: Off" [round-mode]
    b2: btn "Mode: Key" [scan-mode]  
    below
    text "Quantity:"
    f3: field [check-errors-f3]
    text "Description:"
    f4: field
    text 100 ""
    across
    btn 95 "Enter [CTRL+Z]" #"^Z" [enter-item]
    btn 95 "View Data" [view-data]
    do [focus f1] 
] [resize]

This program enables a specialized work flow which is as fast, efficient, and error proof as possible, and it satisfies the exact specifications required to enter data in the unique environment for which it was created. The special modifications are simply additions to the generic inventory program presented at the beginning of the tutorial.

11.2 Receipt Printer

In one of this author's businesses, receipts for rent payments were initially provided using a traditional paper receipt book. This was an error prone process, paper receipts could be damaged and lost, and seaching for information on receipts later was too time consuming. A very quick solution was initially devised by copying all the fields on the paper receipts to a GUI form (similar to the "Generic Text Field Saver" example). That simple program evolved into the following script, which validates correct data entry, requests confirmation before saving, automatically saves audit trail backups, provides simple entry using GUI features such as drop-down selection lists and automatic date/time entry, and displays a nicely formatted text receipt for printing:

REBOL [title: "Cash Receipt"]
make-dir %/M/merchant/documents/
make-dir %/M/merchant/documents/cash_receipts/
make-dir %/M/merchant/documents/cash_receipts/history/
write/append %/M/merchant/documents/cash_receipts/cash_receipts.txt ""
write/append %/M/merchant/documents/cash_receipts.txt ""
view center-face layout [
    across
    style field field 400
    text 50 right "Name: "  name: field return
    text 50 right "Booth: "  booth: field return
    text 50 right "Amount: "  amount: field "$" return
    text 50 right "" paytype: drop-down "Cash" "Check" "Credit" "Other"
        text right 15 "#:" num: field 270 return
    text 50 right "Signed: "  signed: field return
    text 50 right "Date"  date: field 400 (form now) return
    text 50 right "Note: "  note: area "Rent for ..." return
    indent 405 btn 50 "SAVE" [
        if error? try [
            to-integer booth/text to-money amount/text to-date date/text
        ][
            alert {
                ERROR: booth must be a number, amount must be valid money
                amount, date must be a date/time in the default format
                (1-jan-2011/12:00:00-4:00).  Make sure there are no
                additional spaces in the data.  ENTER ANY OTHER
                INFORMATION IN THE "NOTE" FIELD.
            }
            return
        ]
        unless true = request "Confirm Save" [return]
        backup-receipt: rejoin [
            %/M/merchant/documents/cash_receipts/history/  
            now/date "_" 
            replace/all copy form now/time ":" "-"
            ".txt"
        ]
        write 
            backup-receipt 
            read %/M/merchant/documents/cash_receipts/cash_receipts.txt
        write/append 
                %/M/merchant/documents/cash_receipts/cash_receipts.txt 
                receipt-data: reduce [
            newline mold name/text "  "
            mold booth/text "  "
            mold amount/text "  "
            mold paytype/text "  "
            mold num/text "  "
            mold signed/text "  "
            mold date/text "  "
            mold note/text "  "
        ]
        write/append %/M/merchant/documents/cash_receipts.txt receipt-data
        cur-receipt: rejoin [
            %/M/merchant/documents/cash_receipts/
            name/text "_"
            now/date "_" 
            replace/all copy form now/time ":" "-"
            ".txt"
        ]
        write/append cur-receipt reduce [
            newline newline newline
            "             M E R C H A N T S '    R E C E I P T" 
            newline
            "             ____________________________________"
            newline newline newline newline
            "      Name:  " name/text "  " newline newline
            "     Booth:  " booth/text "  " newline newline
            "    Amount:  " amount/text "  " newline newline
            "  Pay Type:  " paytype/text "  " newline newline
            "    Number:  " num/text "  " newline newline
            " Signed by:  " signed/text "  " newline newline
            "      Date:  " date/text "  " newline newline
            "      Note:  " note/text newline newline newline newline
            newline newline newline newline
            "             X _____________________________________________"
            newline newline newline newline
            "             X _____________________________________________"
        ]
        alert "This receipt is not valid until signed by both parties!"
        call/show rejoin ["notepad " to-local-file cur-receipt]
    ]
]

Using the data saved by the program above, the script below can be used to produce a report calculating total rent collected between selected dates:

REBOL [title: "Total "] 
start-date: request-date
end-date: request-date
receipts: load %/m/merchant/documents/cash_receipts/cash_receipts.txt
total: $0
foreach [name booth amount type number signed date notes] receipts [
    date: to-date first parse date "/"
    if ((date >= start-date) and (date <= end-date)) [
        ; print name print date
        total: total + to-money amount
    ]
]
alert form total

Here is a program that displays the entire rent history for every client, prominently noting those who currently owe rent:

REBOL [title: "Rent History and Currently Due Report"]
due-dates: copy ""
total-money: 0
grand-total-monthly: 0
booths: load %booths.txt
foreach [a b c d e f g] booths [if error? try [
    append due-dates rejoin ["Booth " a ", " b newline]
    due-date: copy ""
    parse g [
        thru "[" copy due-date to "]"
    ]
    due-date: parse due-date " "
    if not empty? due-date [
        if error? try [
            either now/date >= (current-date: to-date first due-date) [
                append due-dates rejoin ["    DUE:  " (form current-date)]
                money-is-due: true
            ] [
                append due-dates rejoin ["    " (form current-date)]
                money-is-due: false
            ]
        ] [
            append due-dates "    (Invalid Date)"
        ]
        if error? try [
            current-money: to-money second due-date
            grand-total-monthly: grand-total-monthly + current-money
            if money-is-due = true [
                total-money: total-money + current-money
            ]
            append due-dates rejoin [
                newline "    " (form current-money) newline
            ]
        ] [
            append due-dates rejoin [
                newline "    (Invalid amount)" newline
            ]
        ]
    ]
    append due-dates "-------------------------------------------------^/"
] [alert rejoin ["ERROR: booth " a " " b " " c " " d " " e " " f " " g]] ]
append due-dates rejoin [
    newline newline "Total Due: " total-money
    newline newline "Total Monthly Rent: " grand-total-monthly
]
make-dir %./rent_reports/
change-dir %./rent_reports/
write report-filename: to-file rejoin [
    "rent_" now/date "_" (replace/all to-string now/time ":" "-") ".txt"
] due-dates
call/show rejoin ["notepad " to-local-file what-dir "\" report-filename]

Again, what started with a tiny GUI form for saving a few text fields, evolved into a full featured application set. Only a basic understanding of saving files, concatenating and splitting text, using foreach loops, testing for errors, etc., is required to create all of the code above. The report scripts can be integrated back into the main program's GUI window with code this simple (inside the view layout block):

btn "Rent Due Report" [launch %rentdue.r]
btn "Total Rent Report" [launch %rentcollected.r]

11.3 Advanced Time Clock and Automated Payroll Reports

In the same business as above, a specialized time clock machine with fingerprint validation was initially employed to manage employee payroll and work reports. The software that came with the fingerprint machine was very difficult for managers to use, and the reports it generated were awkward and inadequate for the needs of the business. In order to solve the problem, the following program was created. It simply adds features to the simple "Time Clock" app demonstrated earlier in the tutorial. This version uses an NIST clock script to set the computer's internal clock to the exact correct time (Internet connection is required). To ensure that employees never sign in for others, the program takes a photo of the person performing each signin (the code routine to capture photos is covered later in this text). To enhance security further, a full audit history of every single entry made to the signins, is saved to the hard drive, and each file is uploaded to the company's web server. This simple added feature ensures that signin times cannot be tampered with by anyone who doesn't have approved access:

REBOL [title: "Time Clock"]
insert-event-func [
    either event/type = 'close [
        really: request {
            To restart this program you must also 
            restart the computer.  Really close?
        }
        if really = true [quit]
    ] [event]
]

; Ladislav Mecir's nistclock.r, to ensure the computer's clock
; is set correctly:

do decompress #{
789C6D544B6FDB300CBEFB57B005861D0ADB49BA6081D7B5971D765977688162
087C506D3AD1224B811E09BC61FF7D941C278A13388E2592FAF8FA44CB5B4C0D
EA1D6A53C032819A759664459EFB4FCA32C98DCD566A77A17ABFAAF2B2692ABB
CC199270B9CA945E5D18644C8974C732D3B52D5ACD2BD566F42665D2C7924A55
C024F1B66938078D93958FEFEF33921E9C41B06B6E82DC7225A1551A41351625
299804252B042EA1514E83C14AC9DADCFC4B2017AA62028ED0D0FEAE61DD9AA4
F4F04E5A2EFC02A2408E4BB88329A97813891E41A05CD9F513D8A896B08CCE4F
4B3A249505D45A6932D41D2CA3DC34B21AB6BCDA9C431C11E838FDB64C1BCC99
88635F9A0DDF42A5B65D48630E613FA30A6807B7F4041565078BA02298C8EFF4
73FEAC76F974315F50665651B92CAE50DF78B0C832EFCDC9C02F6E42B54E5A6A
5AA5B4C6D086D443E81D13D4BE62514C62558F22D51E52B872A2EFF649E111E8
3913637D4687432F351A276CE85FBFECBDDCC10831F19DBBE2191EBE42CD9B06
357AD2F418308A3C906280BFCCEA580D187B2DAE605378A1A7FD36D0DEA6A633
16DB8092EEB98C384F5AE8B5A1039ED66F5CD66A6FBE1084755AC2AB76415E31
E3AF01185755680C117E59315BAD4B7F072D1EF93F7238B05FD019A092387C82
8F1BD412C5FD0C96C3AA00A1589D0BFEAE1991F8C320CF6A21C8C308B480966D
2867E52C97C49B70AD82FA405EAB5D65495E96A1B63E111A42D416CF7838BABF
7D41FB12CEBDD2B9DB3E9322FC1395FC27FFA32426A765E04E021378781C07D5
C774744D8EF7BF90698A66ADB4770CFB1F4ADA752CF8C6BA9FCD1BE266248CB7
DFFD9C8941B8741663C94B1842E73642F0C36C3AC94B2A45EDAA9E7121A58E02
1CD6AD0F6ED8EC29261AADC3365A867BBBA698CE046D088A44F1653FA9FB5048
3DF1ECBC60254DC23D272E1D9A98FB29E5472FA3AC26997F66F3B97F7DE4BDE0
3E9BC2B2B8C2EE72B0F894CDAE58086F4183C5D12D9236BE64E7936064D128DD
422C0A792561609FB3E00AD661268F2650F91F6BB4707323070000
} 
make-dir img-dir: %./clock_photos/
unless exists? %employees [
    write %employees {"Nick Antonaccio" "(Add New...)"}
]
cur-employee: copy ""
avicap32.dll: load/library %avicap32.dll
user32.dll: load/library %user32.dll
find-window-by-class: make routine! [
    ClassName [string!] WindowName [integer!] return: [integer!]
] user32.dll "FindWindowA"
sendmessage: make routine! [
    hWnd [integer!] val1 [integer!] val2 [integer!] val3 [integer!]
    return: [integer!]
] user32.dll "SendMessageA"
sendmessage-file: make routine! [
    hWnd [integer!] val1 [integer!] val2 [integer!] val3 [string!]
    return: [integer!]
] user32.dll  "SendMessageA"
cap: make routine! [
    cap [string!] child-val1 [integer!] val2 [integer!] 
    val3 [integer!] width [integer!] height [integer!]
    handle [integer!] val4 [integer!] return: [integer!]
] avicap32.dll "capCreateCaptureWindowA"
log-it: func [inout] [
    if ((cur-employee = "") or (cur-employee = "(Add New...)")) [
        alert "You must select your name." return
    ]
    if set-system-time nist-corrected-time [nist-correction: 0:0]
    cur-time: now
    record: rejoin [
        newline {[} mold cur-employee 
        { "} mold cur-time {" "} inout { "]}
    ]
    either true = request/confirm rejoin [
        record " -- IS YOUR NAME AND THE TIME CORRECT?"
    ] [
        make-dir %./edit_history/
        write/append %time_sheet.txt ""
        write rejoin [
            %./edit_history/time_sheet--
             "_" now/date "_"
             replace/all form now/time ":" "-"
        ] read %time_sheet.txt
        write/append %time_sheet.txt record
        if error? try [
            write ftp://user:pass@site.com/public_html/time_sheet.txt
                read %time_sheet.txt
        ] [alert "Error uploading to web site (saved locally)."]
        alert rejoin [
            uppercase copy cur-employee ", YOU ARE " inout "."
        ]
    ] [
        alert "CANCELED"
        return
    ]
    time-filename: copy replace/all copy to-string cur-time "/" "_"
    time-filename: copy replace/all copy time-filename ":" "+"
    img-file: rejoin [
        img-dir 
        (replace/all copy cur-employee " " "_")
        "_"
        time-filename "_" 
        next find inout " "
        ".bmp"
    ]
    sendmessage cap-result 1085 0 0
    sendmessage-file cap-result 1049 0 img-file
    ; call to-rebol-file img-file
]
timeclock-report: does [
    timeclock-start-date: request-date
    timeclock-end-date: request-date
    totals: copy ""
    names: load %employees
    log: load %time_sheet.txt
    foreach name names [
        if name <> "(Add New...)" [
            times: copy reduce [name]
            foreach record log [
                if name = log-name: record/1 [
                    flag: none
                    date-time: parse record/2 "/"
                    log-date: to-date date-time/1
                    log-time: to-time first parse date-time/2 "-"
                    if (
                        (log-date >= timeclock-start-date) and 
                        (log-date <= timeclock-end-date)
                    ) [
                        previous-flag: flag
                        either record/3 = "CLOCKED IN " [
                            flag: true
                        ] [
                            flag: false
                        ]
                        either flag <> previous-flag [
                            append times log-date
                            append times log-time
                        ] [
                            alert rejoin [
                                "Duplicate successive IN/OUT entry: "
                                name ", " record/2
                            ] 
                        ]
                    ]
                ]
            ]
            append totals rejoin [name ":" newline]
            total-hours: 0
            foreach [in-date in-time out-date out-time] (at times 2) [
                append totals rejoin [
                    newline 
                    "    in: " in-date ", " in-time 
                    "  out: " out-date ", " out-time "    "
                ]
                if error? try [
                    total-hours: total-hours + (out-time - in-time)
                ] [
                    alert rejoin [
                        "Missing login or Missing logout: " name
                    ]
                ]
            ]
            append totals rejoin [
                newline newline
                "    TOTAL HOURS: " total-hours
                newline newline newline
            ]
        ]
    ]
    write filename: copy rejoin [
        %timeclock_report-- timeclock-start-date 
        "_to_" timeclock-end-date ".txt"
    ] totals
    call/show rejoin ["notepad " to-local-file filename]
]
view/new center-face layout/tight [
    image 320x240
    tl1: text-list 320x200 data sort load %employees [
        cur-employee: value
        if cur-employee = "(Add New...)" [
            write/append %employees mold trim request-text/title "Name:"
            tl1/data: sort load %employees show tl1
        ]
    ]
    key #"^~" [
        del-emp: copy to-string tl1/picked
        temp-emp: sort load %employees
        if true = request/confirm rejoin ["REMOVE " del-emp "?"] [
            new-list: head remove/part find temp-emp del-emp 1
            save %employees new-list
            tl1/data: sort load %employees show tl1
            alert rejoin [del-emp " removed."]
        ]
    ]
    across
    btn "Clock IN" [log-it "CLOCKED IN"]
    btn "Clock OUT" [log-it "CLOCKED OUT"]
    btn "Report" [timeclock-report]
    btn "EXIT" [
        sendmessage cap-result 1205 0 0
        sendmessage cap-result 1035 0 0
        free user32.dll   quit
    ]
]
hwnd: find-window-by-class "REBOLWind" 0
cap-result: cap "cap" 1342177280 0 0 320 240 hwnd 0
sendmessage cap-result 1034 0 0
sendmessage cap-result 1077 1 0
sendmessage cap-result 1075 1 0
sendmessage cap-result 1074 1 0
sendmessage cap-result 1076 1 0
do-events

The reports printed by the program above are produced in an easily readable, consistent format. Paychex.com is used to process payroll for the business that uses the script above. Even though the report format is clean, entering payroll figures into the Paychex.com web interface required quite a bit of time each week. In order to speed that process, the following additional script was created. This program enables extremely fast copying and pasting directly into Paychex's custom web interface. The text reports created by the script above can be emailed, copied to the clipboard of any remote machine where the payroll manager is working, and the processed output can be entered instantly into Paychex's web site. Inputting payroll for 30+ employees takes less than a minute, using this script:

REBOL [title: "Enter Time Clock Report into Paychex"]
dec-time: func [tm] [
    qq: (to-decimal second q: parse form round/to tm 00:00:60 ":") / 60 
    write clipboard:// form round/to ((to-decimal q/1) + qq) .01
]
data1: copy read clipboard://
data2: copy parse/all data1 "^/"
foreach line data2 [
     if line = (trim copy line) [print line]
     if find line "TOTAL HOURS:" [
         hours: to-time (last parse line " ")
         if hours <> none [
             dec-time hours
             ask "Paste Into Paychex, Then Press [ENTER]..."
         ]
     ]
]
halt

The script above is very simple, but such a time saving and error reducing routine would have been impossible to create without custom software coding.

Here's another little custom report script that can be used to check the entire audit history of all log-ins for any given employee, starting on any given date, to ensure that no entries have been manually changed (this can be used to compare files on the local server, or on the backup web server):

REBOL [title: "Payroll Audit History Report"]
start: ["John Smith" "18-Mar-2012/8:30:53-4:00" "CLOCKED IN "]
current: find/only (load %./time_sheet.txt) start
erased: copy []
collected: copy []
foreach file read %./edit_history/ [
    if error? try [
        current-period: find/only (load join %./edit_history/ file) start
        if current-period <> none [
           probe length? current-period
           difs: difference current current-period
           append collected difs
        ]
    ] [print file]
]
probe length? current
probe length? final: unique collected
ask "Done..."
editor difference current final
halt

Hopefully, the examples in this section have shed a bit more light on simple ways in which real world custom apps can help maintain data integrity, security, and critically functional customised workflow preferences that are just not possible with generic "office applications" or 1-size-fits-all third party software solutions.

12. More REBOL Language Fundamentals

This section covers a variety of topics that form a more complete understanding of the basic REBOL language.

12.1 Comments

You've already seen that text after a semicolon and before a new line is treated as a comment (ignored entirely by the interpreter). Multi-line comments can be created by enclosing text in square or curly brackets and simply not assigning a label or function to process it. Since this entire program is just a header and comments, it does nothing:

REBOL []
; this is a comment
{
    This is a multi line comment.
    Comments don't do anything in a program.
    They just remind the programmer what's happening in the code.
}
[[
    This is also a multi line comment.
    alert "See...  Nothing."
]] 
comment [
    The "comment" function can be used to clarify that the following
    block does nothing, but it's not necessary.
]

12.2 Function Refinements

Many functions have "refinements" (options separated by "/"):

request-text/default "Text"
request-text/title  "The /title refinement sets this header text"
request-text/title/default  "Name:"  "John Smith"     ; 2 options together
request-text/title/offset "/offset repositions the requester" 10x100
request-pass/offset/title 10x100 "title" alert "Processing"  ; 2 functions
request-file/file %temp.txt          ; default file name
request-file/filter ["*.txt" "*.r"]  ; only show .txt and .r files
request-file/only  ; limit selection to a single file
request-file/save  ; save dialog (instead of open dialog)
request-file/save/file/filter %temp.txt ["*.txt" "*.r"]

Typing "help (function)" in the REBOL interpreter console displays all available refinements for any function.

12.3 White Space and Indentation

Unlike other languages, REBOL does not require any line terminators between expressions (functions, parameters, etc.), and you can insert empty white space (tabs, spaces, newlines, etc.) as desired into code. Notice the use of indentation and comments in the code below. Notice also that the contents of the brackets are spread across multiple lines:

alert rejoin [
    "You chose: "               ; 1st piece of joined data
    (request "Choose one:")     ; 2nd piece of joined data
]

The code above works exactly the same as:

alert rejoin ["You chose: " request "Choose one:"]

ONE CAVEAT: parameters for most functions should begin on the same line as the function word. The following example will not work properly because the rejoin arguments' opening brackets need to be on the same line as the rejoin function:

alert rejoin                    ; This does NOT work. 
[                               ; Put this bracket on the line above.
    "You chose: "
    (request "Choose one:")
]

Blocks often contain other blocks. Such compound blocks are typically indented with consecutive tab stops. Starting and ending brackets are normally placed at the same indentation level. This is conventional in most programming languages, because it makes complex code easier to read, by grouping things visually. For example, the compound block below:

big-block: [[may june july] [[1 2 3] [[yes no] [monday tuesday friday]]]]

can be written as follows to show the beginnings and endings of blocks more clearly:

big-block: [
    [may june july] 
    [ 
        [1 2 3] 
        [
            [yes no]
            [monday tuesday friday]
        ]
    ]
]

probe first big-block
probe second big-block
probe first second big-block
probe second second big-block
probe first second second big-block
probe second second second big-block

Indentation is not required, but it's really helpful.

12.4 Multi Line Strings, Quotes, and Concatenation

Strings of text can be enclosed in quotes or curly brackets:

print "This is a string of text."
print {
    Curly braces are used for
    multi line text strings
    (instead of quotes).
}

alert {To use "quotes" in a text string, put them inside curly braces.}
alert "You can use {curly braces} inside quotes."
alert "'Single quotes' can go inside double quotes..."
alert {'...or inside curly braces'}
alert {"ANY quote symbol" {can actually be used within} 'curly braces'}
alert "In many cases"  alert {curly braces and quotes are interchangable.}

You can print a carriage return using the word "newline" or the characters ^/

print rejoin ["This text if followed by a carriage return." newline]
print "This text if followed by a carriage return.^/"

Clear the console screen using "newpage":

prin newpage

The "rejoin" function CONCATENATES (joins together) values:

rejoin ["Hello " "World"]
rejoin [{Concatenate } {as } {many items } {as } {you } {want.}]
rejoin [request-date {  } request-color {  } now/time {  } $29.99]
alert rejoin ["You chose: " request "Choose one:"] ; CASCADE return values
join {"Join" only concatenates TWO items } {("rejoin" is more powerful).}
print rejoin ["This text is followed by a carriage return." newline]
print "This text is also followed by a carriage return.^/"
prin {'Prin' } prin {doesn't } prin {print } print {a carriage return.}

12.5 More About Variables

The COLON symbol assigns a value to a word label (a "variable")

x: 10
print x
x: x + 1    ; increment variable by 1 (add 1 to the current value of x)
print x
y: "hello"  z: " world"

You can use the "PROBE" function to show RAW DATA assigned to a variable (PRINT formats nice output). Probe is useful for debugging problem code:

y: "hello"  z: " world"
print rejoin [y z]
probe rejoin [y z]   
print join y z

The "prin" function prints values next to each other (without a newline):

y: "hello"  z: " world"
prin y 
prin z

Variables (word labels) ARE ** NOT ** CASE SENSITIVE:

person: "john"
print person   print PERSON   print PeRsOn

You can cascade variable value assignments. Here, all 3 variables are set to "yes ":

value1: value2: value3: "yes "
print rejoin [value1 value2 value3]

The "ask" function gets text input from the user. You can assign that input (the return value of the ask function) directly to a variable label:

name: ask "Enter your name:  "  
print rejoin ["Hello " name]

You can do the same with values returned from requestor functions:

filename: request-file/only
alert rejoin ["You chose " filename]
osfile: to-local-file filename   ; REBOL uses its own multiplatform syntax
to-rebol-file osfile  ; Convert from native OS file notation back to REBOL
the-url: http://website.com/subfolder
split-path the-url   ; "split-path" breaks any file or URL into 2 parts

12.6 Data Types

REBOL automatically knows how to perform appropriate computations on times, dates, IP addresses, coordinate values, and other common types of data:

print 3:30am + 00:07:19                   ; increment time values properly
print now                                 ; print current date and time
print now + 0:0:30                        ; print 30 seconds from now
print now - 10                            ; print 10 days ago
$29.99 * 5                                ; perform math on money values
$29.99 / 7                                ; try this with a decimal value
29.99 / 7
print 23x54 + 19x31                       ; easily add coordinate pairs
22x66 * 2                                 ;  and perform other coordiante
22x66 * 2x3                               ;  math
print 192.168.1.1 + 000.000.000.37        ; easily increment ip addresses
11.22.33.44 * 9        ; note that each IP segment value is limited to 255
0.250.0 / 2       ; colors are represented as tuple values with 3 segments
red / 2                    ; so this is an easy way to adjust color values
view layout [image picture effect [flip]] ; apply effects to image types
x: 12  y: 33  q: 18  p: 7
(as-pair x y) + (as-pair q p)  ; very common in graphics apps using coords
remove form to-money 1 / 233
remove/part form to-time (1 / 233) 6

REBOL also natively understands how to use URLs, email addresses, files/directories, money values, tuples, hash tables, sounds, and other common values in expected ways, simply by the way the data is formatted. You don't need to declare, define, or otherwise prepare such types of data as in other languages - just use them.

To determine the type of any value, use the "type?" function:

some-text:  "This is a string of text"    ; strings of text go between
type? some-text                           ; "quotes" or {curly braces}

some-text:  {
    This is a multi line string of text.
    Strings are a native data type, delineated by
    quotes or curly braces, which enclose text.
    REBOL has MANY other built in data types, all
    delineated by various characters and text formats.
    The "type" function returns a value's data type.
    Below are just a few more native data types:
}                                          
type? some-text

an-integer: 3874904                       ; integer values are just pos-
type? an-integer                          ; itive/negative whole numbers

a-decimal: 7348.39                        ; decimal numbers are recognized
type? a-decimal                           ; by the decimal point

web-site: http://musiclessonz.com         ; URLs are recognized by the
type? web-site                            ; http://, ftp://, etc.

email-address: user@website.com           ; email values are in the
type? email-address                       ; format user@somewebsite.domain

the-file: %/c/myfile.txt                  ; files are preceded by the %
type? the-file                            ; character

bill-amount: $343.56                      ; money is preceded by the $
type? bill-amount                         ; symbol

html-tag: <br>                            ; tags are places between <>
type? html-tag                            ; characters

binary-info:  #{ddeedd}                   ; binary data is put between
type? binary-info                         ; curly braces and preceded by
                                          ; the pound symbol

image: load http://rebol.com/view/bay.jpg ; REBOL can even automatically
type? image                               ; recognize the data type of
                                          ; most common image formats.

a-sound: load %/c/windows/media/tada.wav  ; And sounds too!
a-sound/type

color: red
type? color

color-tuple: 123.54.212                    
type? color-tuple

a-character: #"z"                          
type? a-character

a-word: 'asdf                              
type? a-word

Data types can be specifically "cast" (created, or assigned to different types) using "to-(type)" functions:

numbr: 4729                ; The label 'numbr now represents the integer
                           ;   4729.
strng: to-string numbr     ; The label 'strng now represents a piece of
                           ;   quoted text made up of the characters
                           ;   "4729".  Try adding strng + numbr, and
                           ;   you'll get an error.

; This example creates and adds two coordinate pairs.  The pairs are
; created from individual integer values, using the "to-pair" function:

x: 12  y: 33  q: 18  p: 7
pair1: to-pair rejoin [x "x" y]        ; 12x33
pair2: to-pair rejoin [q "x" p]        ; 18x7
print pair1 + pair2                    ; 12x33 + 18x7 = 30x40

; This example builds and manipulates a time value using the "to-time"
; function:

hour: 3
minute: 45
second: 00
the-time: to-time rejoin [hour ":" minute ":" second]    ; 3:45am
later-time: the-time + 3:00:15
print rejoin ["3 hours and 15 seconds after 3:45 is " later-time]

; This converts REBOL color values (tuples) to HTML colors and visa versa:

to-binary request-color
to-tuple #{00CD00}

Try this list of data type conversion examples:

to-decimal 3874904        ; Now the number contains a decimal point
to-string http://go.com   ; now the web site URL is surrounded by quotes
form web-site             ; "form" also converts various values to string
form $29.99
alert form $29.99         ; the alert function REQUIRES a string parameter
alert $29.99              ; (this throws an error)
5 + 6                     ; you can perform math operations with integers
"5" + "6"                 ; (error) you can't perform math with strings
(to-integer "5") + (to-integer "6")    ; this eliminates the math problem
to-pair [12 43]           ; creates a coordinate pair
as-pair 12 43             ; a better way to create a coordinate pair
to-binary 123.54.212      ; convert a REBOL color value to hex color value
to-binary request-color   ; convert the color chosen by the user, to hex
to-tuple #{00CD00}        ; convert a hex color value to REBOL color value
form to-tuple #{00CD00}   ; covert the hex color value to a string
write/binary %floorplan8.pdf debase read clipboard://  ; email attachment

REBOL has many built-in helper functions for dealing with common data types. Another way to create pair values is with the "as-pair" function. You'll see this sort of pair creation commonly to plot graphics at coordinate points on the screen:

x: 12  y: 33  q: 18  p: 7
print (as-pair x y) + (as-pair q p)    ; much simpler!

Built-in network protocols, native data types, and consistent language syntax for reading, writing, and manipulating data allow you to perform common coding chores easily and intuitively in REBOL. Remember to type or paste every example into the REBOL interpreter to see how each function and language construct operates.

12.7 Random Values

You can create random values of any type:

random/seed now/time   ; always use this line to get real random values
random 50              ; a random number between 0 and 50
random 50x100          ; left side is limited to 50, right limited to 100
random 222.222.222     ; each segment is limited to #s between 0 and 222
random $500
random "asdfqwerty"    ; a random mix of the given characters

12.8 More About Reading, Writing, Loading, and Saving to and from Varied Sources

Thoughout this tutorial, you'll see examples of functions that read and write data to "local files", web sites, the system "clipboard", emails, and other data sources. If you're totally new to programming, a quick explanation of that topic and related terms is helpful here.

It may be familiar that in MS Windows, when you click the "My Computer" (or "Computer") icon on the desktop, you see a list of hard drives, USB flash drives, mapped network drives, and other storage devices attached to the computer:

Data on your computer's permanent hard drive is organized into a tree of folders (or "directories"), each containing individual files and additional branches of nested folders. In Windows, the root directory of your main hard drive is typically called "C:\". C is the letter name given to the disk, and "\" ("backslash") represents the root folder of the directory tree. The REBOL interpreter is installed, by default, in the folder C:\Program Files\rebol\view\

When you perform any sort of read, write, save, load, editor or other function that reads and writes data "on your computer", you are working with files on one of the "local" storage devices attached to the computer (as opposed to a folder on web server, email account, etc.). When using read and write functions, the default location for those files, in a default installation of REBOL, is "C:\Program Files\rebol\view\". The following image of a Windows file selector shows the list of files currently contained in that folder on the author's computer:

In REBOL, the percent character ("%") is used to represent local files. Because REBOL can be used on many operating systems, and because those operating systems all use different syntax to refer to drives, paths, etc., REBOL uses the universal format: %/drive/path/path/.../file.ext . For example, "C:\Program Files\rebol\view\" in Windows is referred to as "%/C/Program%20Files/rebol/view/" in REBOL code. Note that Windows uses backslashes (\), and REBOL uses forward slashes (/) to refer to folders. REBOL converts the "%" syntax to the appropriate operating system format, so that your code can be written once and used on every operating system, without alteration.

The list of files in the image above would be written in REBOL as below. Notice the forward slashes at the end of folder names:

%data/
%desktop/ 
%local/ 
%public/ 
%temp-examples/ 
%console_email.r
%e 
%edit-prefs.r 
%r 
%read-email-header.r 
%rebol.exe 
%temp.txt 
%user.r 
%word-cats.r 
%word-defs.r 
%wordbrowser.r

The following 2 functions convert REBOL file format to your operating system's format, and visa versa. This is particularly useful when dealing with files that contain spaces or other characters:

print to-local-file %/C/Program%20Files/rebol/view/rebol.exe 
print to-rebol-file {C:\Program Files\rebol\view\rebol.exe}

You can use the "change-dir" (or "cd") function to change folders:

change-dir %/c/                     ; changes to the C:\ folder in Windows
cd %/c/                             ; "cd" is a shortcut for "change-dir"

To move "up" a folder from the current directory, use "%../". For example, the following code moves from the default C:\Program Files\rebol\view\ folder, up to C:\Program Files\rebol\, and then to C:\Program Files\:

cd %../
cd %../

Refer to the current folder with "%./". You can read a listing of the files in the current folder, like this:

read %./
probe read %./
editor %./

You can make a new folder within the current folder, using the "make-dir" function. Here are some additional folder functions:

make-dir %./newfolder/
what-dir 
list-dir

You can rename, copy, and delete files within a folder, using these functions:

rename %temp.txt %temp2.txt                             ; change file name
write %temp.txt read %temp2.txt                                ; copy file
delete %temp2.txt

The "write" function writes data to a file. It takes two parameters - a file name to write to, and some data to be written:

write %name.txt "John Smith"

The "read" function reads data from a file:

read %name.txt

You can assign variable labels to data that will be written to a file:

name: "John Smith"
write %name.txt name

Assign variable labels to data read from a file:

loaded-name: read %name.txt
print loaded-name

REBOL's built-in text editor can also read, write, and manipulate text data in files:

editor %name.txt

You can write data to a web site (or any other connected protocol) using the exact same write syntax that is used to write to a file. Writing to a web site "ftp" account requires a username and password:

write ftp://user:pass@website.com/folder/test.txt "Text written by REBOL"

You can read data straight from a web server, an ftp account, an email account, etc. using the same format. Many Internet protocols are built right into the REBOL interpreter. They're understood natively, and REBOL knows exactly how to connect to them without any preparation by the programmer:

editor http://rebol.com                      ; Reads the content of the
                                             ;   document at this URL.
editor pop://user:pass@website.com           ; Reads all emails in this
                                             ;   POP inbox.
editor clipboard://                          ; Reads data that has
                                             ;   been copied/pasted to
                                             ;   the OS clipboard.
print read dns://msn.com                     ; Displays the DNS info
                                             ;   for this address.
print read nntp://public.teranews.com        ; (Hit the [ESC] key to stop
                                             ;   this Usenet listing.)

NOTE: The editor reads, AND allows you to SAVE EDITS back to the server:

editor ftp://user:pass@website.com/public_html/index.html

Transferring data between devices connected by any supported protocol is easy - just read and write:

; read data from a web site, and paste it into the local clipboard:

write clipboard:// (read http://rebol.com)   ; afterward, try pasting into
                                             ; your favorite text editor

; read a page from one web site, and write it to another:

write ftp://user:pass@website2.com (read http://website1.com) 

; again, notice that the "write" function takes TWO parameters

Sending email is just as easy, using a similar syntax:

send user@website.com "Hello"
send user@website.com (read %file.txt)       ; sends an email, with
                                             ; file.txt as the body

The "/binary" modifier is used to read or write binary (non-text) data. You'll use read/binary and write/binary to read and write images, sounds, videos and other non-text files:

write/binary %/c/bay.jpg read/binary http://rebol.com/view/bay.jpg

For clarification, remember that the write function takes two parameters. The first parameter above is "%/c/bay.jpg". The second parameter is the binary data read from http://rebol.com/view/bay.jpg:

write/binary (%/c/bay.jpg) (read/binary http://rebol.com/view/bay.jpg)

The "load" and "save" functions also read and write data, but in the process, automatically format certain data types for use in REBOL. Try this:

; assign the word "picture" to the image "load"ed from a given URL:

picture: load http://rebol.com/view/bay.jpg

; save the image to a given file name, and automatically convert it
; to .png format;

save/png %/c/picture.png picture

; show it in a GUI window:

view layout [image load %/c/picture.png]

"Load" and "save" are used to conveniently manage certain types of data in formats directly usable by REBOL (blocks, images, sounds, DLLs, certain native data structures, etc. can be loaded and used immediately). You'll use "read" and "write" more commonly to store and retrieve typical types of data, exactly byte for byte, to/from a storage medium, when no conversion or formatting is necessary.

All these examples and options may currently come across as confusing. If the topic is feels daunting at the moment, simply accept this section as reference material and continue studying the next sections. You'll become much more familiar with reading and writing as you see the functions in use within real examples.

12.9 Understanding Return Values and the Order of Evaluation

In REBOL, you can put as many functions as you want on one line, and they are all evaluated strictly from left to right. Functions are grouped together automatically with their required data parameter(s). The following line contains two alert functions:

alert "First function" alert "Second function"

Rebol knows to look for one parameter after the first alert function, so it uses the next piece of data on that line as the argument for that function. Next on the line, the interpreter comes across another alert function, and uses the following text as it's data parameter.

Simple requester functions don't require any parameters, but like most functions, they RETURN a useful value. Try pasting these functions directly into the REBOL console to see their return values:

request-text
request-date 
request-color
request-file
request-dir
request-pass

In the following line, the first function, with its refinements "request-pass/offset/title" requires two parameters, so REBOL uses the next two items on the line ("10x100" and "title") as its arguments. After that's complete, the interpreter comes across another "alert" function, and uses the following text, "Processing", as its argument:

request-pass/offset/title 10x100 "title" alert "Processing"

IMPORTANT: In REBOL, the return values (output) from one function can be used directly as the arguments (input) for other functions. Everything is simply evaluated from left to right. In the line below, the "alert" function takes the next thing on the line as it's input parameter, which in this case is not a piece of data, but a function which returns some data (the concatenated text returned by the "rejoin" function):

alert rejoin ["Hello " "there" "!"]

To say it another way, the value returned above by the "rejoin" function is passed to (used as a parameter by) the "alert" function. Parentheses can be used to clarify which expressions are evaluated and passed as parameters to other functions. The parenthesized line below is treated by the REBOL interpreter exactly the same as the line above - it just lets you see more clearly what data the "alert" function puts on screen:

alert ( rejoin ["Hello " "there" "!"] )

Perhaps the hardest part of getting started with REBOL is understanding the order in which functions are evaluated. The process can appear to work backwords at times. In the example below, the "editor" function takes the next thing on the line as it's input parameter, and edits that text. In order for the editor function to begin its editing operation, however, it needs a text value to be returned from the "request-text" function. The first thing the user sees when this line runs, therefore, is the text requester. That appears backwards, compared to the way it's written:

editor (request-text)

Always remember that lines of REBOL code are evaluated from left to right. If you use the return value of one function as the argument for another function, the execution of the whole line will be held up until the necessary return value is processed.

Any number of functions can be written on a single line, with return values cascaded from one function to the next:

alert ( rejoin ( ["You chose: " ( request "Choose one:" ) ] ) )

The line above is typical of common REBOL language syntax. There are three functions: "alert", "rejoin", and "request". In order for the first alert function to complete, it needs a return value from "rejoin", which in turn needs a return value from the "request" function. The first thing the user sees, therefore, is the request function. After the user responds to the request, the selected response is rejoined with the text "You chose: ", and the joined text is displayed as an alert message. Think of it as reading "display (the following text joined together ("you chose" (an answer selected by the user))). To complete the line, the user must first answer the question.

To learn REBOL, it's essential to first memorize and recognize REBOL's many built-in function words, along with the parameters they accept as input, and the values which they return as output. When you get used to reading lines of code as functions, arguments, and return values, read from left to right, the language will quickly begin to make sense.

It should be noted that in REBOL, math expressions are evaluated from left to right like all other functions. There is no "order of precedence", as in other languages (i.e., multiplication doesn't automatically get computed before addition). To force a specific order of evaluation, enclose the functions in parentheses:

print   10  +  12  /  2      ;  22 / 2 = 11
print  (10  +  12) /  2      ;  22 / 2 = 11  (same as without parentheses)
print   10  + (12  /  2)     ;  10 + 6 = 16  (force multiplication first)

REBOL's left to right evaluation is simple and consistent. Parentheses can be used to clarify the flow of code, if ever there's confusion.

12.10 More About Conditional Evaluations

You've already seen the "if" and "either" conditional operations. Math operators are typically used to perform conditional evaluations: = < > <> (equal, less-than, greater-than, not-equal):

if now/time > 12:00 [alert "It's after noon."] 

either now/time > 8:00am [
    alert "It's time to get up!"
][
    alert "You can keep on sleeping."
]

12.10.1 Switch

The "switch" evaluation chooses between numerous functions to perform, based on multiple evaluations. Its syntax is:

switch/default (main value) [
    (value 1) [block to execute if value 1 = main value
    (value 2) [block to execute if value 2 = main value]
    (value 3) [block to execute if value 3 = main value]
    ; etc...
] [default block of code to execute if none of the values match]

You can compare as many values as you want against the main value, and run a block of code for each matching value:

favorite-day:  request-text/title "What's your favorite day of the week?"

switch/default favorite-day [
    "Monday"    [alert "Monday is the worst!  The work week begins..."]
    "Tuesday"   [alert "Tuesdays and Thursdays are both ok, I guess..."]
    "Wednesday" [alert "The hump day - the week is halfway over!"]
    "Thursday"  [alert "Tuesdays and Thursdays are both ok, I guess..."]
    "Friday"    [alert "Yay!  TGIF!"]
    "Saturday"  [alert "Of course, the weekend!"]
    "Sunday"    [alert "Of course, the weekend!"]
] [alert "You didn't type in the name of a day!"]

12.10.2 Case

You can choose between multiple evaluations of any complexity using the "case" structure. If none of the cases evaluate to true, you can use any true value to trigger a default evaluation:

name: "john"
case [
    find name "a" [print {Your name contains the letter "a"}]
    find name "e" [print {Your name contains the letter "e"}]
    find name "i" [print {Your name contains the letter "i"}]
    find name "o" [print {Your name contains the letter "o"}]
    find name "u" [print {Your name contains the letter "u"}]
    true [print {Your name doesn't contain any vowels!}]
]

for i 1 100 1 [
    case [
        (0 = modulo i 3) and (0 = modulo i 5) [print "fizzbuzz"]
        0 = modulo i 3 [print "fizz"]
        0 = modulo i 5 [print "buzz"]
        true [print i]
    ]
]

By default, the case evaluation automatically exits once a true evaluation is found (i.e., in the name example above, if the name contains more than one vowel, only the first vowel will be printed). To check all possible cases before ending the evaluation, use the /all refinement:

name: "brian" 
found: false
case/all [
    find name "a" [print {Your name contains the letter "a"} found: true]
    find name "e" [print {Your name contains the letter "e"} found: true]
    find name "i" [print {Your name contains the letter "i"} found: true]
    find name "o" [print {Your name contains the letter "o"} found: true]
    find name "u" [print {Your name contains the letter "u"} found: true]
    found = false [print {Your name doesn't contain any vowels!}]
]

12.10.3 Multiple Conditions: "and", "or", "all", "any"

You can check for more than one condition to be true, using the "and", "or", "all", and "any" words:

; first set some initial values all to be true:

value1: value2: value3: true

; then set some additional values all to be false:

value4: value5: value6: false

; The following prints "both true", because both the first
; condition AND the second condition are true:

either ( (value1 = true) and (value2 = true) ) [
    print "both true"
] [
    print "not both true"
]

; The following prints "both not true", because the second 
; condition is false:

either ( (value1 = true) and (value4 = true) ) [
    print "both true"
] [
    print "not both true"
]

; The following prints "either one OR the other is true"
; because the first condition is true:

either ( (value1 = true) or (value4 = true) ) [
    print "either one OR the other is true"
] [
    print "neither is true"
]

; The following prints "either one OR the other is true"
; because the second condition is true:

either ( (value4 = true) or (value1 = true) ) [
    print "either one OR the other is true"
] [
    print "neither is true"
]

; The following prints "either one OR the other is true"
; because both conditions are true:

either ( (value1 = true) or (value4 = true) ) [
    print "either one OR the other is true"
] [
    print "neither is true"
]

; The following prints "neither is true":

either ( (value4 = true) or (value5 = true) ) [
    print "either one OR the other is true"
] [
    print "neither is true"
]

For comparisons involving more items, you can use "any" and "all":

; The following lines both print "yes", because ALL comparisons are true.
; "All" is just shorthand for the multiple "and" evaluations:

if ((value1 = true) and (value2 = true) and (value3 = true)) [
    print "yes"
]

if all [value1 = true  value2 = true  value3 = true] [
     print "yes"
]

; The following lines both print "yes" because ANY ONE of the comparisons
; is true. "Any" is just shorthand for the multiple "or" evaluations:

if ((value1 = true) or (value4 = true) or (value5 = true)) [
    print "yes"
]

if any [value1 = true  value4 = true  value5 = true] [
     print "yes"
]

12.11 More About Loops

12.11.1 Forever

"Loop" structures provide programmatic ways to methodically repeat actions, manage program flow, and automate lengthy data processing activities. You've already seen the "foreach" loop structure. The "forever" function creates a simple repeating loop. Its syntax is:

forever [block of actions to repeat]

The following code uses a forever loop to continually check the time. It alerts the user when 60 seconds has passed. Notice the "break" function, used to stop the loop:

alarm-time: now/time + :00:60
forever [if now/time = alarm-time [alert "1 minute has passed" break]]

Here's a more interactive version using some info provided by the user. Notice how the forever loop, if evaluation, and alert arguments are indented to clarify the grouping of related parameters:

event-name: request-text/title "What do you want to be reminded of?"
seconds: to-integer request-text/title "Seconds to wait?"
alert rejoin [
    "It's now " now/time ", and you'll be alerted in " 
    seconds " seconds."
]
alarm-time: now/time + seconds
forever [
    if now/time = alarm-time [
        alert rejoin [
            "It's now "alarm-time ", and " seconds 
            " seconds have passed.  It's time for: " event-name
        ] 
        break
    ]
]

Here's a forever loop that displays/updates the current time in a GUI:

view layout [
    timer: field
    button "Start" [
        forever [
            set-face timer now/time 
            wait 1
        ]
    ]
]

12.11.2 Loop

The "loop" function allows you to repeatedly evaluate a block of code, a specified number of times:

loop 50 [print "REBOL is great!"]

12.11.3 Repeat

Like "loop", the "repeat" function allows you to repeatedly evaluate a block of code, a specified number of times. It additionally allows you to specify a counter variable which is automatically incremented each time through the loop:

repeat count 50 [print rejoin ["This is loop #: " count]]

The above code does the same thing as:

count: 0
loop 50 [
    count: count + 1
    print rejoin ["This is loop #: " count]
]

Another way to write it would be:

for i 1 50 1 [print rejoin ["This is loop #: " i]]

12.11.4 Forall and Forskip

"Forall" loops through a block, incrementing the marked index number of the series as it loops through:

some-names: ["John" "Bill" "Tom" "Mike"]

foreach name some-names [print index? some-names]  ; index doesn't change
forall some-names [print index? some-names]  ; index changes

foreach name some-names [print name]
forall some-names [print first some-names] ; same effect as line above

"Forskip" works like forall, but skips through the block, jumping a periodic number of elements on each loop:

some-names: ["John" "Bill" "Tom" "Mike"]
forskip some-names 2  [print first some-names]

12.11.5 While and Until

The "while" function repeatedly evaluates a block of code while the given condition is true. While loops are formatted as follows:

while [condition] [
    block of functions to be executed while the condition is true
]

This example counts to 5:

x: 1  ; create an initial counter value 
while [x <= 5] [
    alert to-string x 
    x: x + 1
]

In English, that code reads:

"x" initially equals 1. 
While x is less than or equal to 5, display the value of x,
then add 1 to the value of x and repeat.

Some additional "while" loop examples:

while [not request "End the program now?"] [
    alert "Select YES to end the program."
] 
; "not" reverses the value of data received from
; the user (i.e., yes becomes no and visa versa)

alert "Please select today's date" 
while [request-date <> now/date] [
    alert rejoin ["Please select TODAY's date.  It's " now/date]
]

while [request-pass <> ["username" "password"]] [
    alert "The username is 'username' and the password is 'password'"
]

"Until" loops are similar to "while" loops. They do everything in a given block, repeatedly, until the last expression in the block evaluates to true:

x: 10
until [
    print rejoin ["Counting down: " x]
    x: x - 1
    x = 0
]

12.11.6 For

The for function can loop through a series of items in a block, just like "foreach", but using a counted index. The for syntax reads like this: "Assign a (variable word) to refer to an ordinally counted sequence of numbers, begin counting on a (start number), count to an (end number), skipping by this (step number) [use the variable label to refer to each consecutive number in the count]:

REBOL []
for counter 1 10 1 [print counter] 
for counter 10 1 -1 [print counter] 
for counter 10 100 10 [print counter] 
for counter 1 5 .5 [print counter] 
halt

REBOL will properly increment any data type that it understands:

REBOL []
for timer 8:00 9:00 0:05 [print timer] 
for dimes $0.00 $1.00 $0.10 [print dimes] 
for date 1-dec-2005 25-jan-2006 8 [print date]
for alphabet #"a" #"z" 1 [prin alphabet]
halt

You can pick out indexed items from a list, using the incrementally counted numbers in a FOR loop. Just determine the length of the block using the "length?" function:

REBOL []
months: system/locale/months
len: length? months
for i 1 len 1 [
    print rejoin [(pick months i) " is month number " i]
]
halt

This code does the exact same thing as above, using one of the alternate syntaxes instead of "pick":

REBOL []
months: system/locale/months
len: length? months
for i 1 len 1 [
    print rejoin [months/:i " is month number " i]
]
halt

As you've seen, you can pick out consecutive items from a list using counter arithmetic (pick index, pick index + 1, pick index + 2). Within a for structure that uses a skip value, this concept allows you to pick out columns of data:

REBOL []
months: system/locale/months
len: length? months
for i 1 len 3 [
    print rejoin [
        "Months " i " to " (i + 2) " are:" newline newline
        (pick months i) newline
        (pick months (i + 1)) newline
        (pick months (i + 2)) newline 
    ]
]
halt

Here's an example that uses an "if" conditional evaluation to print only names that contain a requested string of text. This provides a functional search:

REBOL []
users: [
    "John Smith" "123 Tomline Lane Forest Hills, NJ" "555-1234"
    "Paul Thompson" "234 Georgetown Pl. Peanut Grove, AL" "555-2345"
    "Jim Persee" "345 Pickles Pike Orange Grove, FL" "555-3456"
    "George Jones" "456 Topforge Court Mountain Creek, CO" ""
    "Tim Paulson" "" "555-5678"
]
search-text: request-text/title/default "Search for:" "t"
for i 1 length? users 3 [
    if find/only (pick users i) search-text [
        print rejoin [
            (pick users i) newline
            (pick users (i + 1)) newline
            (pick users (i + 2)) newline
        ]

    ]
]
halt

To clarify the syntactic difference between "for" and "foreach" loops, here is the same program as above, written using foreach:

REBOL []
users: [
    "John Smith" "123 Tomline Lane Forest Hills, NJ" "555-1234"
    "Paul Thompson" "234 Georgetown Pl. Peanut Grove, AL" "555-2345"
    "Jim Persee" "345 Pickles Pike Orange Grove, FL" "555-3456"
    "George Jones" "456 Topforge Court Mountain Creek, CO" ""
    "Tim Paulson" "" "555-5678"
]
search-text: request-text/title/default "Search for:" "t"
foreach [name address phone] users [
    if find/only name search-text [
        print rejoin [
            name newline
            address newline
            phone newline
        ]

    ]
]
halt

As you can see, the for loop function is useful in almost the exact same way as foreach. It's a bit cryptic, but useful for certain common field selection algorithms which involve non-consecutive fields. You will find that both functions are used in applications of all types that deal with tabular data and lists. You'll see many use cases for each function, as this tutorial progresses - keep your eyes peeled for for and foreach.

The example below uses several loops to alert the user to feed the cat, every 6 hours between 8am and 8pm. It uses a for loop to increment the times to be alerted, a while loop to continually compare the incremented times with the current time, and a forever loop to do the same thing every day, continuously. Notice the indentation:

forever [
    for timer 8:00am 8:00pm 6:00 [
        while [now/time <= timer] [wait :00:01] 
        alert rejoin ["It's now " now/time ".  Time to feed the cat."]
    ]
]

12.12 More About Why/How Blocks are Useful

IMPORTANT: In REBOL, blocks can contain mixed data of ANY type (text and binary items, embedded lists of items (other blocks), variables, etc.):

some-items: ["item1" "item2" "item3" "item4"]
an-image: load http://rebol.com/view/bay.jpg
append some-items an-image

; "some-items" now contains 4 text strings, and an image!

; You can save that entire block of data, INCUDING THE BINARY
; IMAGE data, to your hard drive as a SIMPLE TEXT FILE: 

save/all %some-items.txt some-items

; to load it back and use it later:

some-items: load %some-items.txt
view layout [image fifth some-items]

Take a moment to examine the example above. REBOL's block structure works in a way that is dramatically easy to use compared to other languages and data management solutions (much more simply than most database systems). It's is a very flexible, simple, and powerful way to store data in code! The fact that blocks can hold all types of data using one simple syntactic structure is a fundamental reason it's easier to use than other programming languages and computing tools. You can save/load block code to the hard drive as a simple text file, send it in an email, display it in a GUI, compress it and transfer it to a web server to be downloaded by others, transfer it directly over a point-to-point network connection, or even convert it to XML, encrypt, and store parts of it in a secure multiuser database to be accessed by other programming languages, etc...

Remember, all programming, and computing in general, is essentially about storing, organizing, manipulating, and transferring data of some sort. REBOL makes working with all types of data very easy - just put any number of pieces of data, of any type, in between two brackets, and that data is automatically searchable, sortable, storable, transferable, and otherwise usable in your programs.

12.12.1 Evaluating Variables in Blocks: Compose, Reduce, Pick and More

You will often find that you want to refer to an item in a block by its index (position number), as in the earlier 'some-items' example:

view layout [image some-items/5]

You may not, however, always know the specific index number of the data item you want to access. For example, as you insert data items into a block, the index position of the last item changes (it increases). You can obtain the index number of the last item in a block simply by determining the number of items in the block (the position number of the last item in a block is always the same as the total number of items in the block). In the example below, that index number is assigned the variable word "last-item":

last-item: length? some-items

Now you can use that variable to pick out the last item:

view layout [image (pick some-items last-item)]

; In our earlier example, with 5 items in the block, the
; line above evaluates the same as:

view layout [image (pick some-items 5)]

You can refer to other items by adding and subtracting index numbers:

alert pick some-items (last-item - 4)

There are several other ways to do the exact same thing in REBOL. The "compose" function allows variables in parentheses to be evaluated and inserted as if they'd been typed explicitly into a code block:

view layout compose [image some-items/(last-item)]

; The line above appears to the interpreter as if the following
; had been typed:

view layout [image some-items/5]

The "compose" function is very useful whenever you want to refer to data at variable index positions within a block. The "reduce" function can also be used to produce the same type of evaluation. Function words in a reduced block should begin with the tick (') symbol:

view layout reduce ['image some-items/(last-item)]

Another way to use variable values explicitly is with the ":" format below. This code evaluates the same as the previous two examples:

view layout [image some-items/:last-item]

Think of the colon format above as the opposite of setting a variable. As you've seen, the colon symbol placed after a variable word sets the word to equal some value. A colon symbol placed before a variable word gets the value assigned to the variable, and inserts that value into the code as if it had been typed explicitly.

You can use the "index?" and "find" functions to determine the index position(s) of any data you're searching for in a block:

index-num: index? (find some-items "item4")

Any of the previous 4 formats can be used to select the data at the determined variable position:

print pick some-items index-num
print compose [some-items/(index-num)]
print reduce [some-items/(index-num)]  
; no function words are used in the block above, so no ticks are required
print some-items/:index-num

Here's an example that displays variable image data contained in a block, using a foreach loop. The "compose" function is used to include dynamically changeable data (image representations), as if that data had been typed directly into the code:

photo1: load http://rebol.com/view/bay.jpg
photo2: load http://rebol.com/view/demos/palms.jpg

; The REBOL interpreter sees the following line as if all the code
; representing the above images had been typed directly in the block:

photo-block: compose [(photo1) (photo2)]

foreach photo photo-block [view layout [image photo]]

For additional detailed information about using blocks and series functions see http://www.rebol.com/docs/core23/rebolcore-6.html.

12.13 REBOL Strings

In REBOL, a "string" is simply a series of characters. If you have experience with other programming languages, this can be one of the sticking points in learning REBOL. REBOL's solution is actually a very powerful, easy to learn and consistent with the way other operations work in the language. Proper string management simply requires a good understanding of list functions. Take a look at the following examples to see how to do a few common operations:

the-string: "abcdefghijklmnopqrstuvwxyz"

; Left String:  (get the left 7 characters of the string):

copy/part the-string 7

; Right String:  (Get the right 7 characters of the string):

copy at tail the-string -7

; Mid String 1:  (get 7 characters from the middle of the string,
; starting with the 12th character):

copy/part (at the-string 12) 7

; Mid String 2:  (get 7 characters from the middle of the string,
; starting 7 characters back from the letter "m"):

copy/part (find the-string "m") -7

; Mid String 3:  (get 7 characters from the middle of the string,
; starting 12 characters back from the letter "t"):

copy/part (skip (find the-string "t") -12) 7

; 3 different ways to get just the 7th character:

the-string/7 
pick the-string 7
seventh the-string

; Change "cde" to "123"

replace the-string "cde" "123"

; Several ways to change the 7th character to "7"

change (at the-string 7) "7"
poke the-string 7 #"7"  ; the pound symbol refers to a single character
poke the-string 7 (to-char "7")  ; another way to use single characters
print the-string

; Remove 15 characters, starting at the 3rd position:

remove/part (at the-string 3) 15
print the-string

; Insert 15 characters, starting at the 3rd position:

insert (at the-string 3) "cdefghijklmnopq"
print the-string

; Insert 3 instances of "-+" at the beginning of the string:

insert/dup head the-string "-+ " 3
print the-string

; Replace every instance of "-+ " with " ":

replace/all the-string "-+ "  " "
print the-string

; Remove spaces from a string (type "? trim" to see all its refinements!):

trim the-string
print the-string

; Get every third character from the string:

extract the-string 3

; Get the ASCII value for "c" (ASCII 99):

to-integer third the-string

; Get the character for ASCII 99 ("c"):

to-char 99

; Convert the above character value to a string value:

to-string to-char 99

; Convert any value to a string:

to-string now
to-string $2344.44
to-string to-char 99
to-string system/locale/months

; An even better way to convert values to strings:

form now
form $2344.44
form to-char 99
form system/locale/months  ; convert blocks to nicely formed strings

; Covert strings to a block of characters:

the-block: copy []
foreach item the-string [append the-block item]
probe the-block

REBOL's series functions are very versatile. Often, you can devise several ways to do the same thing:

; Remove the last part of a URL:

the-url: "http://website.com/path"
clear at the-url (index? find/last the-url "/")
print the-url

; Another way to do it:

the-url: "http://website.com/path"
print copy/part the-url (length? the-url)-(length? find/last the-url "/")

(Of course, REBOL has a built-in helper function to accomplish the above goal, directly with URLs):

the-url: http://website.com/path
print first split-path the-url

There are a number of additional functions that can be used to work specifically with string series. Run the following script for an introduction:

string-funcs: [
    build-tag checksum clean-path compress debase decode-cgi decompress
    dehex detab dirize enbase entab import-email lowercase mold parse-xml
    reform rejoin remold split-path suffix? uppercase
]    
echo %string-help.txt  ; "echo" saves console activity to a file
foreach word string-funcs [
    print "___________________________________________________________^/"
    print rejoin ["word:  " uppercase to-string word]  print "" 
    do compose [help (to-word word)]
]
echo off
editor at read %string-help.txt 4

See http://www.rebol.com/docs/dictionary.html and http://rebol.com/docs/core23/rebolcore-8.html for more information about the above functions.

13. More Essential Topics

13.1 Built-In Help and Online Resources

The "help" function displays required syntax for any REBOL function:

help print

"?" is a synonym for "help":

? print

The "what" function lists all built-in words:

what

Together, those two words provide a built-in reference guide for the entire core REBOL language. Here's a script that saves all the above documentation to a file. Give it a few seconds to run:

echo %words.txt what echo off   ; "echo" saves console activity to a file
echo %help.txt
foreach line read/lines %words.txt [
    word: first to-block line
    print "___________________________________________________________^/"
    print rejoin ["word:  " uppercase to-string word]  print "" 
    do compose [help (to-word word)]
]
echo off
editor at read %help.txt 4

You can use help to search for defined words and values, when you can't remember the exact spelling of the word. Just type a portion of the word (hitting the tab key will also show a list of words for automatic word completion):

? to-         ; shows a list of all built-in type conversions
? reques      ; shows a list of built-in requester functions
? "load"      ; shows all words containing the characters "load"
? "?"         ; shows all words containing the character "?"

Here are some more examples of ways to search for useful info using help:

? datatype!   ; shows a list of built-in data types
? function!   ; shows a list of built-in functions
? native!     ; shows a list of native (compiled C code) functions
? char!       ; shows a list of built-in control characters
? tuple!      ; shows a list of built-in colors (RGB tuples)
? .gif        ; shows a list of built-in .gif images

You can view the source code for built-in "mezzanine" (non-native) functions with the "source" function. There is a huge volume of REBOL code accessible right in the interpreter, and all of the mezzanine functions were created by the language's designer, Carl Sassenrath. Studying mezzanine source is a great way to learn more about advanced REBOL code patterns:

source help
source request-text
source view
source layout
source ctx-viewtop  ; try this:  view layout [image load ctx-viewtop/13]

The "word browser" script is a useful tool for finding, cross referencing, and learning about all the critical functions in REBOL:

write %wordbrowser.r read http://re-bol.com/wordbrowser.r
do %wordbrowser.r

13.1.1 The REBOL System Object, and Help with GUI Widgets

"Help system" displays the contents of the REBOL system object, which contains many important settings and values. You can explore each level of the system object using path notation, like this:

? system/console/history        ; the current console session history
? system/options
? system/locale/months
? system/network/host-address

You can find info about all of REBOL's GUI components in "system/view/VID":

? system/view/VID

The system/view/VID block is so important, REBOL has a built-in short cut to refer to it:

? svv

You'll find a list of REBOL's GUI widgets in "svv/vid-styles". Use REBOL's "editor" function to view large system sections like this:

editor svv/vid-styles

Here's a script that neatly displays all the words in the above "svv/vid-styles" block:

foreach i svv/vid-styles [if (type? i) = word! [print i]]

Here's a more concise way to display the above widgets, using the "extract" function:

probe extract svv/vid-styles 2

This script lets you browse the object structure of each widget:

view layout [
    text-list data (extract svv/vid-styles 2) [
        a/text: select svv/vid-styles value
        show a focus a
    ]
    a: area 500x250 
]

REBOL's GUI layout words are available in "svv/vid-words":

? svv/vid-words

The following script displays all the images in the svv/image-stock block:

b: copy [] 
foreach i svv/image-stock [if (type? i) = image! [append b i]]
v: copy [] foreach i b [append v reduce ['image i]]
view layout v

The changeable attributes ("facets") available to all GUI widgets are listed in "svv/facet-words":

editor svv/facet-words

Here's a script that neatly displays all the above facet words:

b: copy [] 
foreach i svv/facet-words [if (not function? :i) [append b to-string i]]
view layout [text-list data b]

Some GUI widgets have additional facet words available. The following script displays all such functions, and their extra attributes:

foreach i (extract svv/vid-styles 2) [
    x: select svv/vid-styles i
    ; additional facets are held in a "words" block:
    if x/words [
        prin join i ": "
        foreach q x/words [
            if not (function? :q) [prin join q " "]
        ]
        print ""
    ]
]

To examine the function(s) that handle any of the additional facets for the widgets above, type the path to the widget's "words" block, i.e.:

svv/vid-styles/TEXT-LIST/words

For more information on system/view/VID, see http://www.mail-archive.com/rebol-bounce@rebol.com/msg01898.html and http://www.rebol.org/ml-display-message.r?m=rmlHJNC.

It's important to note that you can SET any system value. Just use a colon, like when assigning variable values:

system/user/email: user@website.com

Familiarity with the system object yields many useful tools.

13.1.2 Viewtop Resources

The REBOL desktop that appears by default when you run the view.exe interpreter can be used as a gateway into a world of "Rebsites" that developers use to share useful code. Surfing the public rebsites is a great way to explore the language more deeply. All of the code in the rebol.org archive, and much more, is available on the rebsites. When typing at the interpreter console, the "desktop" function brings up the REBOL desktop (also called the "Viewtop"):

desktop

Click the "REBOL" or "Public" folders to see hundreds of interesting demos and useful examples. Source code for every example is available by right-clicking individual program icons and selecting "edit". You don't need a web browser or any other software to view the contents of Rebsites - the Viewtop and all its features are part of the REBOL executable. You can learn volumes about the REBOL language using only the resources built directly into the 600k interpreter!

For detailed, categorized, and cross-referenced information about built-in functions, see the REBOL Dictionary rebsite, found in the REBOL desktop folder REBOL->Tools (an HTML version is also available at http://www.rebol.com/docs/dictionary.html).

13.1.3 Online Documentation, The Mailing List and The AltME Community Forum

If you can't find answers to your REBOL programming questions using built-in help and resources, the first place to look is http://rebol.com/docs.html. Googling online documentation also tends to provide quick results, since the word "REBOL" is uncommon.

To ask a question directly of other REBOL developers, you can join the community mailing list by sending an email to rebol-request@rebol.com , with the word "subscribe" in the subject line. Use your normal email program, or just paste the following code into your REBOL interpreter (be sure your email account settings are set up correctly in REBOL):

send rebol-request@rebol.com "subscribe"

You can also ask questions of numerous gurus and regular users in AltME, a messaging program which makes up the most active forum of REBOL users around the world. Rebol.org maintains a searchable history of several hundred thousand posts from both the mailing list and AltME, along with a rich script archive. The REBOL user community is friendly, knowledgeable and helpful, and you will typically find answers to just about any question already in the archives. Unlike other programming communities, REBOL does not have a popular web based support forum. AltME is the primary way that REBOL developers interact. If you want to speak with others, you must download the AltME program and set up a user account (it's fast and easy to do). Just follow the instructions at http://www.rebol.org/aga-join.r.

13.2 Saving and Running REBOL Scripts

So far in this tutorial, you've been typing or copying/pasting code snippets directly into the REBOL interpreter. As you begin to work with longer examples and full programs, you'll need to save your scripts for later execution. Whenever you save a REBOL program to a text file, the code must begin with the following bit of header text:

REBOL []

That header tells the REBOL interpreter that the file contains a valid REBOL program. You can optionally document any information about the program in the header block. The "title" variable in the header block is displayed in the title bar of GUI program windows:

REBOL [
    title:  "My Program"
    author: "Nick Antonaccio"
    date:   29-sep-2009
]
view layout [text 400 center "Look at the title bar."]

The code below is a web cam video viewer program. Type in or copy/paste the complete code source below into a text editor such as Windows Notepad or REBOL's built-in text editor (type "editor none" at the REBOL console prompt). Save the text as a file called "webcam.r" on your C:\ drive.

REBOL [title: "Webcam Viewer"]

; try http://www.webcam-index.com/USA/ for more webcam links.

temp-url: "http://209.165.153.2/axis-cgi/jpg/image.cgi"
while [true]  [
    webcam-url: to-url request-text/title/default "Web cam URL:" temp-url
    either attempt [webcam: load webcam-url] [
        break
    ] [
        either request [
            "That webcam is not currently available." "Try Again" "Quit"
        ] [
            temp-url: to-string webcam-url
        ] [
            quit
        ]
    ] 
] 
resize-screen: func [size] [
    webcam/size: to-pair size
    window/size: (to-pair size) + 40x72
    show window
]
window: layout [
    across 
    btn "Stop" [webcam/rate: none show webcam]
    btn "Start" [
        webcam/rate: 0 
        webcam/image: load webcam-url 
        show webcam
    ]
    rotary "320x240" "640x480" "160x120" [
        resize-screen to-pair value 
    ]
    btn "Exit" [quit] return
    webcam: image load webcam-url  320x240 
    with [
        rate: 0
        feel/engage: func [face action event][
            switch action [
                time [face/image: load webcam-url show face]
            ] 
        ] 
    ] 
]
view center-face window

Once you've saved the webcam.r program to C:\, you can run it in any one of the following ways:

  1. If you've already installed REBOL on your computer, just double-click your saved ".r" script file (find the C:\webcam.r file icon in your file explorer (click My Computer -> C: -> webcam.r)). By default, during REBOL's initial installation, all files with a ".r" extension are associated with the interpreter. They can be clicked and run as if they're executable programs, just like ".exe" files. The REBOL interpreter automatically opens and executes any selected ".r" text file. This is the most common way to run REBOL scripts, and it works the same way on all major graphic operating systems. If you want other people to be able to run your scripts, just have them download and install the tiny REBOL interpreter - it only takes a few seconds.
  2. Use the built-in editor in REBOL. Type "editor %/c/webcam.r" at the interpreter prompt, or type "editor none" and copy/paste the script into the editor. Pressing F5 in the editor will automatically save and run the script. This is a convenient way to work with scripts, and enables REBOL to be its own simple, self contained IDE.
  3. Type "do %/c/webcam.r" into the REBOL interpreter.
  4. Scripts can be run at the command line. In Windows, copy rebol.exe and webcam.r to the same folder (C:\), then click Start -> Run, and type "C:\rebol.exe C:\webcam.r" (or open a DOS box and type the same thing). Those commands will start the REBOL interpreter and do the webcam.r code. You can also create a text file called webcam.bat, containing the text "C:\rebol.exe C:\webcam.r" . Click on the webcam.bat file in Windows, and it'll run those commands. In Unix, you can also run scripts at scheduled times with Cron. Just enter the path to the script.
  5. Use a program such as XpackerX to package and distribute the program. XpackerX allows you to wrap the REBOL interpreter and webcam.r program into a single executable file that has a clickable icon, and automatically runs both files. That allows you to create a single file executable Windows program that can be distributed and run like any other application. Just click it and run... (this technique is covered in the next section).
  6. Buy the commercial "SDK" version of REBOL, which provides the most secure method of packaging REBOL applications.

VERY IMPORTANT: To turn off the default security requester that continually asks permission to read/write the hard drive, type "secure none" in the REBOL interpreter, and then run the program with "do {filename}". Running "C:\rebol.exe -s {filename}" does the same thing . The "-s" launches the REBOL interpreter without any security features turned on, making it behave like a typical Windows program.

13.3 "Compiling" REBOL Programs - Distributing Packaged .EXE Files

The REBOL.exe interpreter is tiny and does not require any installation to operate properly. By packaging it, your REBOL script(s), and any supporting data file(s) into a single executable with an icon of your choice, XpackerX works like a REBOL 'compiler' that produces regular Windows programs that look and act just like those created by other compiled languages. To do that, you'll need to create a text file in the following format (save it as "template.xml"):

<?xml version="1.0"?>
<xpackerdefinition>
    <general>
        <!--shown in taskbar -->
        <appname>your_program_name</appname>
        <exepath>your_program_name.exe</exepath>
        <showextractioninfo>false</showextractioninfo>
        <!-- <iconpath>c:\icon.ico</iconpath> -->
    </general>
    <files>
        <file>
            <source>your_rebol_script.r</source>
            <destination>your_rebol_script.r</destination>
        </file>
        <file>
            <source>C:\Program Files\rebol\view\Rebol.exe</source>
            <destination>rebol.exe</destination>
        </file>
        <!--put any other data files here -->
    </files>
    <!-- $FINDEXE, $TMPRUN, $WINDIR, $PROGRAMDIR, $WINSYSDIR -->
    <onrun>$TMPRUN\rebol.exe -si $TMPRUN\your_rebol_script.r</onrun>
</xpackerdefinition>

Just download the free XpackerX program and alter the above template so that it contains the filenames you've given to your script(s) and file(s), and the correct path to your REBOL interpreter. Run XpackerX, and it'll spit out a beautifully packaged .exe file that requires no installation. Your users do not need to have REBOL installed to run this type of executable. To them it appears and runs just like any other native compiled Windows program. What actually happens is that every time your packaged .exe file runs, the REBOL interpreter and your script(s)/data file(s) are unzipped into a temporary folder on your computer. When your script is done running, the temporary folder is deleted.

Most modern compression (zip) applications have an "sfx" feature that allows you to create .exe packages from zip files. You can create a packaged REBOL .exe in the same way as XpackerX using just about any sfx packaging application (there are dozens of freeware zip/compression applications that can do this - use the one you're most familiar with).

The program "iexpress.exe" found on all versions of Windows (starting with Windows XP), is a popular choice for creating SFX files, because no additional software needs to be installed. Just click Start -> Run or Start -> Search Programs and Files, and type "iexpress". Follow the wizards to name the package, choose included files (the REBOL interpreter, scripts, images, etc.), and other options. Settings for any .exe you create with iexpress will be saved in a .sed file, which you can reload and make changes to later. This makes for quick re-"compilation" of updated scripts.

There is an explanation of how to use the NSIS install creator to make REBOL .exe's here. This is helpful if you want to adjust registry settings and make other changes to the computer system while installing your program.

To create a self-extracting REBOL executable for Linux, first create a .tgz file containing all the files you want to distribute (the REBOL interpreter, your script(s), any external binary files, etc.). For the purposes of this example, name that bundle "rebol_files.tgz". Next, create a text file containing the following code, and save it as "sh_commands":

#!/bin/sh
SKIP=`awk '/^__REBOL_ARCHIVE__/ { print NR + 1; exit 0; }' $0`
tail +$SKIP $0 | tar xz    
exit 0
__REBOL_ARCHIVE__

Finally, use the following command to combine the above script file with the bundled .tgz file:

cat sh_commands rebol_files.tgz > rebol_program.sh

The above line will create a single executable file named "rebol_program.sh" that can be distributed and run by end users. The user will have to set the file permissions for rebol_program.sh to executable before running it ("chmod +x rebol_program.sh"), or execute it using the syntax "sh rebol_program.sh".

13.4 Common REBOL Errors, and How to Fix Them

Listed below are solutions to a variety of common errors you'll run into when first experimenting with REBOL:

1) "** Syntax Error: Script is missing a REBOL header" - Whenever you "do" a script that's saved as a file, it must contain at least a minimum required header at the top of the code. Just include the following text at the beginning of the script:

REBOL []

2) "** Syntax Error: Missing ] at end-of-script" - You'll get this error if you don't put a closing bracket at the end of a block. You'll see a similar error for unclosed parentheses and strings. The code below will give you an error, because it's missing a "]" at the end of the block:

fruits: ["apple" "orange" "pear" "grape"
print fruits

Instead it should be:

fruits: ["apple" "orange" "pear" "grape"]
print fruits

Indenting blocks helps to find and eliminate these kinds of errors.

3) "** Script Error: request expected str argument of type: string block object none" - This type of error occurs when you try to pass the wrong type of value to a function. The code below will give you an error, because REBOL automatically interprets the website variable as a URL, and the "alert" function requires a string value:

website: http://rebol.com
alert website

The code below solves the problem by converting the URL value to a string before passing it to the alert function:

website: to-string http://rebol.com
alert website

Whenever you see an error of the type "expected _____ argument of type: ___ ____ ___ ...", you need to convert your data to the appropriate type, using one of the "to-(type)" functions. Type "? to-" in the REBOL interpreter to get a list of all those functions.

4) "** Script Error: word has no value" - Miss-spellings will elicit this type of error. You'll run into it any time you try to use a word that isn't defined (either natively in the REBOL interpreter, or by you, in previous code):

wrod: "Hello world"
print word

5) If an error occurs in a "view layout" block, and the GUI becomes unresponsive, type "unview" at the interpreter command line and the broken GUI will be closed. To restart a stopped GUI, type "do-events". To break out of any endless loop, or to otherwise stop the execution of any errant code, just hit the [Esc] key on your keyboard.

6) "** User Error: Server error: tcp 550 Access denied - Invalid HELO name (See RFC2821 4.1.1.1)" and "** User Error: Server error: tcp -ERR Login failed.", among others, are errors that you'll see when trying to send and receive emails. To fix these errors, your mail server info needs to be set up in REBOL's user settings. The most common way to do that is to edit your mail account info in the graphic Viewtop or by using the "set-net" function (http://www.rebol.com/docs/words/wset-net.html). You can also set everything manually - this is how to adjust all the individual settings:

system/schemes/default/host: your.smtp.address
system/schemes/default/user: username
system/schemes/default/pass: password
system/schemes/pop/host: your.pop.address
system/user/email: your.email@site.com

7) Here's a quirk of REBOL that doesn't elicit an error, but which can cause confusing results, especially if you're familiar with other languages:

unexpected: [
    empty-variable: ""
    append empty-variable "*"
    print empty-variable
]

do unexpected
do unexpected
do unexpected

The line:

empty-variable: ""

doesn't re-initialize the variable to an empty state. Instead, every time the block is run, "empty-variable" contains the previous value. In order to set the variable back to empty, as intended, use the word "copy" as follows:

expected: [
    empty-variable: copy ""
    append empty-variable "*"
    print empty-variable
]

do expected
do expected
do expected

8) Load/Save, Read/Write, Mold, Reform, etc. - another point of confusion you may run into initially with REBOL has to do with various words that read, write, and format data. When saving data to a file on your hard drive, for example, you can use either of the words "save" or "write". "Save" is used to store data in a format more directly usable by REBOL. "Write" saves data in a raw, 'unREBOLized' form. "Load" and "read" share a comparable relationship. "Load" reads data in a way that is more automatically understood and put to use in REBOL code. "Read" opens data in exactly the format it's saved, byte for byte. Generally, data that is "save"d should also be "load"ed, and data that's "write"ed should be "read". For more information, see the following REBOL dictionary entries:

http://rebol.com/docs/words/wload.html

http://rebol.com/docs/words/wsave.html

http://rebol.com/docs/words/wread.html

http://rebol.com/docs/words/wwrite.html

Other built-in words such as "mold" and "reform" help you deal with text in ways that are either more human-readable or more natively readable by the REBOL interpreter. For a helpful explanation, see http://www.rebol.net/cookbook/recipes/0015.html.

9) Order of precedence - REBOL expressions are always evaluated from left to right, regardless of the operations involved. If you want specific mathematical operators to be evaluated first, they should either be enclosed in parenthesis or put first in the expression. For example, to the REBOL interpreter:

2 + 4 * 6

is the same as:

(2 + 4) * 6  ; the left side is evaluated first

== 6 * 6

== 36

This is contrary to other familiar evaluation rules. In many languages, for example, multiplication is typically handled before addition. So, the same expression:

2 + 4 * 6

is treated as:

2 + (4 * 6)  ; the multiplication operator is evaluated first

== 2 + 24

== 26

Just remember, evaluation is always left to right, without exception.

10) You may run into problems when copying/pasting interactive console scripts directly into the REBOL interpreter, especially when the code contains functions such as "ask", which require a response from the user before the remainder of the script is evaluated (each line of the script simply runs, as the pasting operation completes, without any response from the user, leaving necessary variables unassigned). To fix such interactivity problems when copying/pasting console code into the interpreter, simply wrap the entire script in square brackets and then "do" that block: do [...your full script code...]. This will force the entire script to be loaded before any of the code is evaluated. If you want to run the code several times, simply assign it a word label, and then run the word label as many times as needed: do x: [...your full script code...] do x do x do x .... This saves you from having to paste the code more than once. Another effective option, especially with large scripts, is to run the code from the clipboard using "do read clipboard://". This performs much faster than watching large amounts of text paste into the console.

13.4.1 Trapping Errors

There are several simple ways to keep your program from crashing when an error occurs. The words "error?" and "try" together provide a way to check for and handle expected error situations. For example, if no Internet connection is available, the code below will crash abruptly with an error:

html: read http://rebol.com

The adjusted code below will handle the error more gracefully:

if error? try [html: read http://rebol.com] [
    alert "Unavailable."
]

The word "attempt" is an alternative to the "error? try" routine. It returns the evaluated contents of a given block if it succeeds. Otherwise it returns "none":

if not attempt [html: read http://rebol.com] [
    alert "Unavailable."
]

To clarify, "error? try [block]" evaluates to true if the block produces an error, and "attempt [block]" evaluates to false if the block produces an error.

For a complete explanation of REBOL error codes, see: http://www.rebol.com/docs/core23/rebolcore-17.html.

14. Creating Web Applications using REBOL CGI

The Internet provides a fantastic scope of added potential capability to business applications. Network connectivity allows multiple users to share data easily, anywhere in the world. The "web page" interface allows users to input data and view computed output using virtually any Internet connected device (computers, phones, tablets, etc.). The "web page" paradigm and generalized workflow is already familiar to an overwhelming majority of technically savvy users.

In CGI web applications, HTML forms on a web site act as the user interface (GUI) for scripts that run on a web server. Users typically type text into fields, select choices from drop down lists, click check boxes, and otherwise enter data into form "widgets" on a web page, and then click a Submit button when done. The submitted data is transferred to, and processed by, a script that you've stored at a specified URL (Internet address) on your web server. Data output from the script is then sent back to the user's browser and displayed on screen as a dynamically created web page. CGI programs of that sort, running on web sites, are among the most common types of computer application in contemporary use. PHP, Python, Java, PERL, and ASP are popular languages used to accomplish similar Internet programming tasks, but if you know REBOL, you don't need to learn them. REBOL's CGI interface makes Internet programming very easy.

In order to create REBOL CGI programs, you need an available web server. A web server is a computer attached to the Internet, which constantly runs a program that stores and sends out web page text and data, when requested from an Internet browser running on another computer. The most popular web serving application is Apache. Most small web sites are typically run on shared web server hosting accounts, rented from a data center for a few dollars per month (see http://www.lunarpages.com - they're REBOL friendly). While setting up a web server account, you can register an available domain name (i.e, www.yourwebsitename.com). When web site visitors type your ".com" domain address into their browser, they see files that you've created and saved into a publicly accessible file folder on your web server computer. Web hosting companies typically provide a collection of web based software tools that allow you to upload, view, edit, and manage files, folders, email, and other resources on your server. The most popular of these tools is cPanel. No matter what language you use to program web apps, registering a domain, purchasing hosted space, and learning to manage files and resources with tools such as cPanel, is a required starting point. Lunarpages and HostGator are two recommended hosts for REBOL CGI scripting. Full powered web site hosting, with a preconfigured cPanel interface, unlimited space and bandwidth, and all the tools needed to create professional web sites and apps, are available for less than $10 per month.

In order for REBOL CGI scripts to run, the REBOL interpreter must be installed on your web server. To do that, download from rebol.com the correct version of the REBOL interpreter for the operating system on which your web server runs (most often some type of Linux). Upload it to your user path on your web server, and set the permissions to allow it to be executed (typically "755"). Ask your web site host if you don't understand what that means. http://rebol.com/docs/cgi1.html#section-2.2 has some basic information about how to install REBOL on your server. If you don't have an online web server account, you can download a full featured free Apache web server package that will run on your local Windows PC, from http://www.uniformserver.com.

14.1 An HTML Crash Course

In order to create any sort of CGI application, you need to understand a bit about HTML. HTML is the layout language used to format text and GUI elements on all web pages. HTML is not a programming language - it doesn't have facilities to process or manipulate data. It's simply a markup format that allows you to shape the visual appearance of text, images, and other items on pages viewed in a browser.

In HTML, items on a web page are enclosed between starting and ending "tags":

<STARTING TAG>Some item to be included on a web page</ENDING TAG>

There are tags to effect the layout in every possible way. To bold some text, for example, surround it in opening and closing "strong" tags:

<STRONG>some bolded text</STRONG>

The code above appears on a web page as: some bolded text.

To italicize text, surround it in < i > and < / i > tags:

<i>some italicized text</i>

That appears on a web page as: some italicized text.

To create a table with three rows of data, do the following:

<TABLE border=1>
    <TR><TD>First Row</TD></TR>
    <TR><TD>Second Row</TD></TR>
    <TR><TD>Third Row</TD></TR>
</TABLE>

Notice that every

<opening tag>

in HTML code is followed by a corresponding

</closing tag>

Some tags surround all of the page, some tags surround portions of the page, and they're often nested inside one another to create more complex designs.

A minimal format to create a web page is shown below. Notice that the title is nested between "head" tags, and the entire document is nested within "HTML" tags. The page content seen by the user is surrounded by "body" tags:

<HTML>
    <HEAD>
        <TITLE>Page title</TITLE>
    </HEAD>
    <BODY>
        A bunch of text and <i>HTML formatting</i> goes here...
    </BODY>
</HTML>

If you save the above code to a text file called "yourpage.html", upload it to your web server, and surf to http://yourwebserver.com/yourpage.html , you'll see in your browser a page entitled "Page title", with the text "A bunch of text and HTML formatting goes here...". All web pages work that way - this tutorial is in fact just an HTML document stored on the author's web server account. Click View -> Source in your browser, and you'll see the HTML tags that were used to format this document.

14.1.1 HTML Forms and Server Scripts - the Basic CGI Model

The following HTML example contains a "form" tag inside the standard HTML head and body layout. Inside the form tags are a text input field tag, and a submit button tag:

<HTML>
    <HEAD><TITLE>Data Entry Form</TITLE></HEAD>
    <BODY>
        <FORM ACTION="http://yourwebserver.com/your_rebol_script.cgi">
            <INPUT TYPE="TEXT" NAME="username" SIZE="25">
            <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="Submit">
        </FORM>
    </BODY>
</HTML>

Forms can contain tags for a variety of input types: multi-line text areas, drop down selection boxes, check boxes, etc. See http://www.w3schools.com/html/html_forms.asp for more information about form tags.

You can use the data entered into any form by pointing the action address to the URL at which a specific REBOL script is located. For example, 'FORM ACTION="http://yourwebserver.com/your_rebol_script.cgi"' in the above form could point to the URL of the following CGI script, which is saved as a text file on your web server. When a web site visitor clicks the submit button in the above form, the data is sent to the following program, which in turn does some processing, and prints output directly to the user's web browser. NOTE: Remember that in REBOL curly brackets are the same as quotes. Curly brackets are used in all the following examples, because they allow for multiline content and they help improve readability by clearly showing where strings begin and end:

#!/home/your_user_path/rebol/rebol -cs
REBOL []
print {content-type: text/html^/}  
; the line above is the same as:  print "content-type: text/html^/"
submitted: decode-cgi system/options/cgi/query-string

print {<HTML><HEAD><TITLE>Page title</TITLE></HEAD><BODY>}
print rejoin [{Hello } second submitted {!}]
print {</BODY></HTML>}

In order for the above code to actually run on your web server, a working REBOL interpreter must be installed in the path designated by "/home/your_user_path/rebol/rebol -cs".

The first 4 lines of the above script are basically stock code. Include them at the top of every REBOL CGI script. Notice the "decode-cgi" line - it's the key to retrieving data submitted by HTML forms. In the code above, the decoded data is assigned the variable name "submitted". The submitted form data can be manipulated however desired, and output is then returned to the user via the "print" function. That's important to understand: all data "print"ed by a REBOL CGI program appears directly in the user's web browser (i.e., to the web visitor who entered data into the HTML form). The printed data is typically laid out with HTML formatting, so that it appears as a nicely formed web page in the user's browser.

Any normal REBOL code can be included in a CGI script - you can perform any type of data storage, retrieval, organization, and manipulation that can occur in any other REBOL program. The CGI interface just allows your REBOL code to run online on your web server, and for data to be input/output via web pages which are also stored on the web server, accessible by any visitor's browser.

14.2 A Standard CGI Template to Memorize

Most short CGI programs typically print an initial HTML form to obtain data from the user. In the initial printed form, the action address typically points back to the same URL address as the script itself. The script examines the submitted data, and if it's empty (i.e., no data has been submitted), the program prints the initial HTML form. Otherwise, it manipulates the submitted data in way(s) you choose and then prints some output to the user's web browser in the form of a new HTML page. Here's a basic example of that process, using the code above:

#!/home/your_user_path/rebol/rebol -cs
REBOL []
print {content-type: text/html^/}
submitted: decode-cgi system/options/cgi/query-string

; The 4 lines above are the standard REBOL CGI headers.
; The line below prints the standard HTML, head and body
; tags to the visitor's browser:

print {<HTML><HEAD><TITLE>Page title</TITLE></HEAD><BODY>}

; Next, determine if any data has been submitted.
; Print the initial form if empty.  Otherwise, process 
; and print out some HTML using the submitted data.  
; Finally, print the standard closing "body" and "html"
; tags, which were opened above:

either empty? submitted [
    print {
        <FORM ACTION="http://yourwebserver.com/this_rebol_script.cgi">
        <INPUT TYPE="TEXT" NAME="username" SIZE="25">
        <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="Submit">
        </FORM>
        </BODY></HTML>
    }
] [ 
    print rejoin [{Hello } second submitted {!}]
    print {</BODY></HTML>}
]

Using the above standard outline, you can include any required HTML form(s), along with all executable code and data required to make a complete CGI program, all in one script file. Memorize it.

15. Example CGI Applications

15.1 Form Mail

Here's a REBOL CGI form-mail program that prints an initial form, then sends an email to a given address containing the user-submitted data:

#!/home/youruserpath/rebol/rebol -cs
REBOL []
print {content-type: text/html^/}
submitted: decode-cgi system/options/cgi/query-string

; the following account info is required to send email:

set-net [from_address@website.com  smtp.website.com]

; print a more complicated HTML header:

print read %template_header.html

; if some form data has been submitted to the script:

if not empty? submitted [
    sent-message: rejoin [
        newline {INFO SUBMITTED BY WEB FORM} newline newline
        {Time Stamp: } (now + 3:00) newline
        {Name: } submitted/2 newline 
        {Email: } submitted/4 newline
        {Message: } submitted/6 newline 
    ]

    send/subject to_address@website.com sent-message "FORM SUBMISSION"

    html: copy {}
    foreach [var value] submitted [
        repend html [<TR><TD> mold var </TD><TD> mold value </TD></TR>]
    ]
    print {<font size=5>Thank You!</font> <br><br>
        The following information has been sent: <BR><BR>}
    print rejoin [{Time Stamp: } now + 3:00]
    print {<BR><BR><table>}
    print html
    print {</table>}
    ;  print a more complicated HTML footer:
    print read %template_footer.html
    quit
]

; if no form data has been submitted, print the initial form:

print {
    <CENTER><TABLE><TR><TD>
    <BR><strong>Please enter your info below:</strong><BR><BR>
    <FORM ACTION="http://yourwebserver.com/this_rebol_script.cgi">
    Name: <BR> <INPUT TYPE="TEXT" NAME="name"><BR><BR>
    Email: <BR> <INPUT TYPE="TEXT" NAME="email"><BR><BR>
    Message: <BR>
    <TEXTAREA cols=75 name=message rows=5></TEXTAREA> <BR><BR>
    <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="Submit">
    </FORM>
    </TD></TR></TABLE></CENTER>
}
print read %template_footer.html

The template_header.html file used in the above example can include the standard required HTML outline, along with any formatting tags and static content that you'd like, in order to present a nicely designed page. A basic layout may include something similar to the following:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD><TITLE>Page Title</TITLE>    
<META http-equiv=Content-Type content="text/html; 
    charset=windows-1252">
</HEAD>    
<BODY bgColor=#000000>
<TABLE align=center background="" border=0 
    cellPadding=20 cellSpacing=2 height="100%" width="85%">
<TR>
<TD background="" bgColor=white vAlign=top>

The footer closes any tables or tags opened in the header, and may include any static content that appears after the CGI script (copyright info, logos, etc.):

</TD>
</TR>
</TABLE>
<TABLE align=center background="" border=0 
    cellPadding=20 cellSpacing=2 width="95%">
<TR>
<TD background="" cellPadding=2 bgColor=#000000 height=5>
<P align=center><FONT color=white size=1>Copyright  2009
    Yoursite.com.  All rights reserved.</FONT>
</P>
</TD>
</TR>
</TABLE>
</BODY>
</HTML>

15.2 A Generic Drop Down List Application

The following example demonstrates how to automatically build lists of days, months, times, and data read from a file, using dynamic loops (foreach, for, etc.). The items are selectable from drop down lists in the printed HTML form:

#!/home/youruserpath/rebol/rebol -cs
REBOL []
print {content-type: text/html^/}
submitted: decode-cgi system/options/cgi/query-string

print {<HTML><HEAD><TITLE>Dropdown Lists</TITLE></HEAD><BODY>}

if not empty? submitted [
    print rejoin [{NAME SELECTED: } submitted/2 {<BR><BR>}]
    selected: rejoin [
        {TIME/DATE SELECTED: }
        submitted/4 { } submitted/6 {, } submitted/8
    ]
    print selected
    quit
]

; If no data has been submitted, print the initial form:

print {<FORM ACTION="http://yourwebserver.com/your_rebol_script.cgi">
   SELECT A NAME:  <BR> <BR>}
names: read/lines %users.txt
print {<select NAME="names">}
foreach name names [prin rejoin [{<option>} name]]
print {</option> </select> <br> <br>}

print { SELECT A DATE AND TIME: }
print rejoin [{(today's date is } now/date {)} <BR><BR>]

print {<select NAME="month">}
foreach m system/locale/months [prin rejoin [{<option>} m]]
print {</option> </select>}

print {<select NAME="date">} 
for daysinmonth 1 31 1 [prin rejoin [{<option>} daysinmonth]]
print {</option> </select>}

print {<select NAME="time">
for time 10:00am 12:30pm :30 [prin rejoin [{<option>} time]]
for time 1:00 10:00 :30 [prin rejoin [{<option>} time]]
print {</option> </select> <br> <br>}

print {<INPUT TYPE="SUBMIT" NAME="Submit" VALUE="Submit"></FORM>}

The "users.txt" file used in the above example may look something like this:

nick
john
jim
bob

15.3 Photo Album

Here's a simple CGI program that displays all photos in the current folder on a web site, using a foreach loop:

#! /home/path/public_html/rebol/rebol -cs
REBOL [title: "Photo Viewer"]
print {content-type: text/html^/}
print {<HTML><HEAD><TITLE>Photos</TITLE></HEAD><BODY>}
print read %template_header.html

folder: read %.
count: 0
foreach file folder [
    foreach ext [".jpg" ".gif" ".png" ".bmp"] [
        if find file ext [
            print [<BR> <CENTER>]
            print rejoin [{<img src="} file {">}]
            print [</CENTER>]
            count: count + 1
        ]
    ]
]
print {<BR>}
print rejoin [{Total Images: } count]
print read %template_footer.html

Notice that there's no "submitted: decode-cgi system/options/cgi/query-string" code in the above example. That's because the above script doesn't make use of any data submitted from a form.

15.4 Simple Interactive REBOL Web Site Console

Here's a simple but powerful script that allows you to type REBOL code into an HTML text area, and have that code execute directly on your web server. The results of the code are then displayed in your browser. This essentially functions as a remote console for the REBOL interpreter on your server. You can use it to run REBOL code, or to call shell programs directly on your web site - very powerful! DO NOT run this on your web server if you're concerned at all about security!:

#! /home/path/public_html/rebol/rebol276 -cs
REBOL [Title: "CGI Remote Console"]
print {content-type: text/html^/}
print {<HTML><HEAD><TITLE>Console</TITLE></HEAD><BODY>}
submitted: decode-cgi system/options/cgi/query-string

; If no data has been submitted, print form to request user/pass:

if ((submitted/2 = none) or (submitted/4 = none)) [
    print {
        <STRONG>W A R N I N G  -  Private Server, Login Required:</STRONG>
        <BR><BR>
        <FORM ACTION="./console.cgi">
        Username: <INPUT TYPE=text SIZE="50" NAME="name"><BR><BR>
        Password: <INPUT TYPE=text SIZE="50" NAME="pass"><BR><BR>
        <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="Submit">
        </FORM>
    }
    quit
]

; If code has been submitted, print the output:

entry-form: [
    print {
        <CENTER><FORM METHOD="get" ACTION="./console.cgi">
        <INPUT TYPE=hidden NAME=submit_confirm VALUE="command-submitted">
        <TEXTAREA COLS="100" ROWS="10" NAME="contents"></TEXTAREA><BR><BR>
        <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="Submit">
        </FORM></CENTER></BODY></HTML>
    }
]

if submitted/2 = "command-submitted" [
    write %commands.txt join "REBOL[]^/" submitted/4
    ; The "call" function requires REBOL version 2.76:
    call/output/error 
        {/home/path/public_html/rebol/rebol276 -qs commands.txt}
        %conso.txt %conse.txt
    do entry-form
    print rejoin [
        {<CENTER>Output: <BR><BR>}
        {<TABLE WIDTH=80% BORDER="1" CELLPADDING="10"><TR><TD><PRE>}
        read %conso.txt
        {</PRE></TD></TR></TABLE><BR><BR>}
        {Errors: <BR><BR>}
        read %conse.txt
        {</CENTER>}
    ]
    quit
]

; Otherwise, check submitted user/pass, then print form for code entry:

username: submitted/2 password: submitted/4 
either (username = "user") and (password = "pass") [
    ; if user/pass is ok, go on
][
    print "Incorrect Username/Password." quit
]

do entry-form

Upload the script to your server, rename it "console.cgi", set it to executable, and change the path to your REBOL interpreter (2 places in the script). Then try running the following example code:

print 352 + 836
? system/locale/months 
call "ls -al"

15.5 Attendance

Here's an example that allows users to check attendance at various weekly events, and add/remove their names from each of the events. It stores all the user information in a flat file (simple text file) named "jams.db":

#! /home/path/public_html/rebol/rebol -cs
REBOL [title: "event.cgi"]
print {content-type: text/html^/}
print {<HTML><HEAD><TITLE>Event Sign-Up</TITLE></HEAD><BODY>}

jams: load %jam.db

a-line: [] loop 65 [append a-line "-"]
a-line: trim to-string a-line

print {
    <hr> <font size=5>" Sign up for an event:"</font> <hr><BR>
    <FORM ACTION="http://yourwebsite.com/cgi-bin/event.cgi">
    Student Name:
    <input type=text size="50" name="student"><BR><BR>
    ADD yourself to this event:       "
    <select NAME="add"><option>""<option>"all"
}
foreach jam jams [prin rejoin [{<option>} jam/1]]
print {
    </option> </select> <BR> <BR>
    REMOVE yourself from this event:
    <select NAME="remove"><option>""<option>"all"
}
foreach jam jams [prin rejoin [{<option>} jam/1]]
print {
    </option> </select> <BR> <BR>
    <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="Submit">
    </FORM>
}

print-all: does [
    print [<br><hr><font size=5>]
    print " Currently scheduled events, and current attendance:"
    print [</font><br>]
    foreach jam jams [
        print rejoin [a-line {<BR>} jam/1 {BR} a-line {<BR>}]
        for person 2 (length? jam) 1 [
            print jam/:person
            print {<BR>}
        ]
        print {<BR>}
    ]
    print {</BODY></HTML>}
]

submitted: decode-cgi system/options/cgi/query-string

if submitted/2 <> none [
    if ((submitted/4 = "") and (submitted/6 = "")) [
        print {
            <strong> Please try again. You must choose an event.</strong>
        }
        print-all
        quit
    ]
    if ((submitted/4 <> "") and (submitted/6 <> "")) [
        print {
            <strong> Please try again. Choose add OR remove.</strong>
        }
        print-all
        quit
    ]
    if submitted/4 = "all" [
        foreach jam jams [append jam submitted/2]
        save %jam.db jams
        print {
            <strong> Your name has been added to every event:</strong>
        }
        print-all
        quit
    ]
    if submitted/6 = "all" [
        foreach jam jams [
            if find jam submitted/2 [
                remove-each name jam [name = submitted/2]
                save %jam.db jams
            ]
        ]
        print {
            <strong> Your name has been removed from all events:</strong>
        }
        print-all
        quit
    ]
    foreach jam jams [
        if (find jam submitted/4) [
            append jam submitted/2
            save %jam.db jams
            print {
                <strong> Your name has been added to the selected event:
                </strong>
            }
            print-all
            quit    
        ]
    ]
    found: false
    foreach jam jams [
        if (find jam submitted/6) [
            if (find jam submitted/2) [
                remove-each name jam [name = submitted/2]
                save %jam.db jams
                print {
                    <strong>
                    Your name has been removed from the selected event:
                    </strong>
                }
                print-all
                quit
                found: true
            ]
        ]
    ]
    if found <> true [
        print {
            <strong> That name is not found in the specified event!"
            </strong>
        }
        print-all
        quit
    ]
]

print-all

Here is a sample of the "jam.db" data file used in the above example:

["Sunday September 16, 4:00 pm"
    "Nick Antonaccio" "Ryan Gaughan" "Mark Carson"]
["Sunday September 23, 4:00 pm"
    "Nick Antonaccio" "Ryan Gaughan" "Mark Carson"]
["Sunday September 30, 4:00 pm"
    "Nick Antonaccio" "Ryan Gaughan" "Mark Carson"]

15.6 Bulletin Board

Here's a simple web site bulletin board program:

#! /home/path/public_html/rebol/rebol -cs
REBOL [title: "Jam"]
print {content-type: text/html^/}
print read %template_header.html
; print {<HTML><HEAD><TITLE>Bulletin Board</TITLE></HEAD><BODY>}

bbs: load %bb.db

print {
    <center><table border=1 cellpadding=10 width=600><tr><td>
    <center><strong><font size=4>
    Please REFRESH this page to see new messages.
    </font></strong></center>
}

print-all: does [
    print {<br><hr><font size=5> Posted Messages: </font> <br><hr>}
    foreach bb (reverse bbs) [
        print rejoin [
            {<BR>Date/Time: } bb/2 {    }
            {"Name: } bb/1 {<BR><BR>} bb/3 {<BR><BR><HR>}
        ]
    ]
]

submitted: decode-cgi system/options/cgi/query-string

if submitted/2 <> none [
    entry: copy []
    append entry submitted/2
    append entry to-string (now + 3:00)
    append entry submitted/4
    append/only bbs entry
    save %bb.db bbs
    print {<BR><strong>Your message has been added: </strong><BR>}
]

print-all

print {
    <font size=5> Post A New Public Message:</font><hr>
    <FORM ACTION="http://website.com/bb/bb.cgi">
    <br> Your Name:  <br>
    <input type=text size="50" name="student"><BR><BR>
    Your Message: <br>
    <textarea name=message rows=5 cols=50></textarea><BR><BR>
    <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="Post Message">
    </FORM>
    </td></tr></table></center>
}
print read %template_footer.html

Here's an example data file for the program above:

[
    [
        "Nick Antonaccio"
        "8-Nov-2006/4:55:59-8:00"
        {
            WELCOME TO OUR PUBLIC BULLETIN BOARD.
             Please keep the posts clean cut and on topic.
            Thanks and have fun!
        }
    ]
]

15.7 GET vs POST Example

The default format for REBOL CGI data is "GET". Data submitted by the GET method in an HTML form is displayed in the URL bar of the user's browser. If you don't want users to see that data displayed, or if the amount of submitted data is larger then can be contained in the URL bar of a browser, the "POST" method should be used. To work with the POST method, the action in your HTML form should be:

<FORM METHOD="post" ACTION="./your_script.cgi">

You must also use the "read-cgi" function below to decode the submitted POST data in your REBOL script. This example creates a password protected online text editor, with an automatic backup feature:

#!/home/path/public_html/rebol/rebol -cs
REBOL []
print {content-type: text/html^/}
print {<HTML><HEAD><TITLE>Edit Text Document</TITLE></HEAD><BODY>}

; submitted: decode-cgi system/options/cgi/query-string

; We can't use the normal line above to decode, because
; we're using the POST method to submit data (because data
; from the textarea may get too big for the GET method). 
; Use the following standard function to process data from 
; a POST method instead:

read-cgi: func [/local data buffer][
    switch system/options/cgi/request-method [
        "POST" [
            data: make string! 1020
            buffer: make string! 16380
            while [positive? read-io system/ports/input buffer 16380][
                append data buffer
                clear buffer
            ]
        ]
        "GET" [data: system/options/cgi/query-string]
    ]
    data
]

submitted: decode-cgi read-cgi

; if document.txt has been edited and submitted:

if submitted/2 = "save" [ 
    ; save newly edited document:
    write to-file rejoin ["./" submitted/6 "/document.txt"] submitted/4
    print ["Document Saved."]
    print rejoin [
        {<META HTTP-EQUIV="REFRESH" CONTENT="0; 
            URL=http://website.com/folder/}
        submitted/6 {">}
    ]
    quit
]

; if user is just opening page (i.e., no data has been submitted 
; yet), request user/pass:

if ((submitted/2 = none) or (submitted/4 = none)) [
    print {
        <strong>W A R N I N G  -  Private Server, Login Required:
        </strong><BR><BR>
        <FORM ACTION="./edit.cgi">
        Username: <input type=text size="50" name="name"><BR><BR>
        Password: <input type=text size="50" name="pass"><BR><BR>
        <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="Submit">
        </FORM>
    }
    quit
]

; check user/pass against those in userlist.txt, 
; end program if incorrect:

userlist: load %userlist.txt
folder: submitted/2 
password: submitted/4
response: false
foreach user userlist [
    if ((first user) = folder) and (password = (second user)) [
        response: true
    ]
]
if response = false [print {Incorrect Username/Password.} quit]

; if user/pass is ok, go on...

; backup (before changes are made):

cur-time: to-string replace/all to-string now/time {:} {-}
document_text: read to-file rejoin [{./} folder {/document.txt}]
write to-file rejoin [
    {./} folder {/} now/date {_} cur-time {.txt}] document_text

; note the POST method in the HTML form:

prin {
    <strong>Be sure to SUBMIT when done:</strong><BR><BR>
    <FORM method="post" ACTION="./edit.cgi">
    <INPUT TYPE=hidden NAME=submit_confirm VALUE="save">
    <textarea cols="100" rows="15" name="contents">
}
;
; The following line is what we want to do, but it won't work for
; HTML documents which contain <textarea>s
;
; print document_text
;
; The following line fixes the problem:
;
prin replace/all document_text {</textarea>} {&lt\/textarea&gt;}
print {</textarea><BR><BR>}
print rejoin [{<INPUT TYPE=hidden NAME=folder VALUE="} folder {">}]
print {<INPUT TYPE="SUBMIT" NAME="Submit" VALUE="Submit">}
print {</FORM>}
print {</BODY></HTML>}

15.8 Group Note System

Earlier in the tutorial, a full featured note sharing system was presented to allow groups of users to exchange messages. This CGI program allows users to enter and display notes using the exact same data files saved by the desktop program. The desktop version of the application and this web program are 100% interoperable - messages entered with the desktop app are immediately viewable using this CGI, and vice-versa.

Notice that the "read-cgi" function is used in the fourth line. In recent versions of REBOL, that function is built-in, so it does not need to be defined in the code (it's a good idea to include the function definition, in case the script is ever used on a web server that has an older version of REBOL):

#! ../rebol276 -cs
REBOL [title: "Group Notes"]
print {content-type: text/html^/}
submitted: decode-cgi read-cgi
url: ftp://user:pass@site.com/public_html/Notes
print {
    <center><table border=0 cellpadding=10 width=600><tr><td>
}
if submitted/2 <> none [
    if error? try [
        write/lines/append url rejoin [
            "^/^/" now " (" submitted/2 "):  " submitted/4
        ]
    ] [print "ERROR: Not Saved" quit]
]
print {<pre>}
if error? try [notes: copy read/lines url] [write url notes: ""]
display: copy {}
count: 0
remove/part notes 2
foreach note reverse notes [
    either note = "" [
        note: {<br>}
    ] [
        count: count + 1
        note: rejoin [count ") "note]
    ]
    append display note
]
print display
print {
    </td></tr></table>
    <FORM ACTION="http://re-bol.com/notes.cgi">
        <table border=0 cellPadding=0 cellSpacing=4 width=600>
        <tr><td width=10%>Name:</td>
        <td><input type=text size="65" name="username"></td></tr>
        <tr><td width=10%>Message:</td>
        <td><textarea name=message rows=5 cols=50></textarea></td></tr>
        <tr><td></td><td>
        <input type="submit" name="submit" value="Submit">
        </td></tr></table>
    </FORM>
    </td></tr></table></center>
}

15.9 Generic Form Handler

The following is a generic form handler that can be used to save GET or POST data to a text file. It's a useful replacement for generic form mailers, and makes the data much more accessible later by other scripts:

#!/home/path/public_html/rebol/rebol -cs
REBOL []
print {content-type: text/html^/}

read-cgi: func [/local data buffer][
    switch system/options/cgi/request-method [
        "POST" [
            data: make string! 1020
            buffer: make string! 16380
            while [positive? read-io system/ports/input buffer 16380][
                append data buffer
                clear buffer
            ]
        ]
        "GET" [data: system/options/cgi/query-string]
    ]
    data
]
submitted: decode-cgi read-cgi

print {
    <HTML><HEAD><TITLE>Your Form Has Been Submitted</TITLE></HEAD>
    <BODY><CENTER><TABLE border=0 cellPadding=10 width="80%"><TR><TD>
}

entry: rejoin [{[^/ "Time Stamp:" } {"} form (now + 3:00) {"^/}]
foreach [title value] submitted [
    entry: rejoin [entry { } {"} mold title {" } mold value {^/}]
]
append entry {]^/}
write/append %submitted_forms.txt entry

html: copy ""
foreach [title value] submitted [
    repend html [
        <TR><TD width=20%> mold title </TD><TD> mold value </TD></TR>
    ]
]

print rejoin [
    {
         <FONT size=5>Thank You! The following information has been
         submitted: </FONT><BR><BR>Time Stamp:
    } 
    now + 3:00  {<BR><BR><TABLE border=1 cellPadding=10 width="100%">}
    html  {</TABLE><BR>}
    {  
        To correct any errors or to submit forms for additional people,
        please click the [BACK] button in your browser, make any 
        changes, and resubmit the form.  You'll hear from us shortly.
        Thank you!<BR><BR><CENTER><FONT size=1>
        Copyright  2009 This Web Site.  All rights reserved.</FONT>
        </CENTER></TD></TR></CENTER></BODY></HTML>
    }
]

quit

Here's a basic form example that could be processed by the above script. You can add as many text, textareas, and other form items as desired, and the script will save all the submitted data (the action link in the form below assumes that the script above is saved in the text file named "form.cgi"):

<FORM action="form.cgi">
    Name:<BR><INPUT type="TEXT" name="name"><BR><BR>
    Email:<BR><INPUT type="TEXT" name="email"><BR><BR>
    Message:<BR>
        <TEXTAREA cols="75" rows="5" name="message">
        </TEXTAREA><BR><BR>
    <INPUT type="SUBMIT" name="Submit" value="Submit">
</FORM>

The script below can be used on a desktop PC to easily view all the forms submitted at the script above. It provides nice GUI navigation, message count, sort by any data column, etc.:

REBOL [title: "CGI form submission viewer"]

sort-column: 4  ; even numered cols contain data (2nd col is time stamp)
signups: load http://yoursite.com/submitted_forms.txt
do create-list: [
    name-list: copy []
    foreach item signups [append name-list (pick item sort-column)]
]
view center-face layout [
    the-list: text-list 600x150 data name-list [
        foreach item signups [
            if (pick item sort-column) = value [
                dt: copy ""
                foreach [label data] item [
                    dt: rejoin [
                        dt newline label "  " data 
                    ]
                ]
                a/text: dt
                show a
            ]
        ]
    ]
    a: area 600x300 across
    btn "Sort by..." [
        sort-column: to-integer request-text/title/default {
            Data column to list:} "4"
        do create-list
        the-list/data: name-list
        show the-list
    ]
    tab text join (form length? signups) " entries."
]

Here's another script that removes the title columns and reduces the form data into a usable format. Possibilities with managing form data like this are endless:

submissions: load http://yoursite.com/submitted_forms.txt
do create-list: [
    data: copy []
    foreach block submissions [append/only data (extract/index block 2 4)]
    datastring: copy {}
    foreach block data [
        datastring: join datastring "[^/"
        foreach item block [datastring: rejoin [datastring item newline]]
        datastring: join datastring "]^/^/"
    ]
    editor datastring
]

15.10 File Uploader

The following example demonstrates how to upload files to your web server using the decode-multipart-form-data function by Andreas Bolka:

#! /home/path/public_html/rebol/rebol -cs
REBOL [Title: "HTTP File Upload"]
print {content-type: text/html^/}
print {<HTML><HEAD><TITLE>File Upload</TITLE></HEAD>}
print {<BODY><br><br><center><table width=95% border=1>}
print {<tr><td width=100%><br><center>}

read-cgi: func [/local data buffer][
    switch system/options/cgi/request-method [
        "POST" [
            data: make string! 1020
            buffer: make string! 16380
            while [positive? read-io system/ports/input buffer 16380][
                append data buffer
                clear buffer
            ]
        ]
        "GET" [data: system/options/cgi/query-string]
    ]
    data
]

submitted: read-cgi

if submitted/2 = none [
    print {
        <FORM ACTION="./upload.cgi" 
        METHOD="post" ENCTYPE="multipart/form-data">
            <strong>Upload File:</strong><br><br> 
            <INPUT TYPE="file" NAME="photo"> <br><br>
            <INPUT TYPE="submit" NAME="Submit" VALUE="Upload">  
        </FORM>
        <br></center></td></tr></table></BODY></HTML>
    }
    quit
]

decode-multipart-form-data: func [
    p-content-type
    p-post-data
    /local list ct bd delim-beg delim-end non-cr non-lf non-crlf mime-part
] [
    list: copy []
    if not found? find p-content-type "multipart/form-data" [return list]
    ct: copy p-content-type
    bd: join "--" copy find/tail ct "boundary="
    delim-beg: join bd crlf
    delim-end: join crlf bd
    non-cr:     complement charset reduce [ cr ]
    non-lf:     complement charset reduce [ newline ]
    non-crlf:   [ non-cr | cr non-lf ]
    mime-part:  [
        ( ct-dispo: content: none ct-type: "text/plain" )
        delim-beg ; mime-part start delimiter
        "content-disposition: " copy ct-dispo any non-crlf crlf
        opt [ "content-type: " copy ct-type any non-crlf crlf ]
        crlf ; content delimiter
        copy content
        to delim-end crlf ; mime-part end delimiter
        ( handle-mime-part ct-dispo ct-type content )
    ]
    handle-mime-part: func [
        p-ct-dispo
        p-ct-type
        p-content
        /local tmp name value val-p
    ] [
        p-ct-dispo: parse p-ct-dispo {;="}
        name: to-set-word (select p-ct-dispo "name")
        either (none? tmp: select p-ct-dispo "filename")
               and (found? find p-ct-type "text/plain") [
            value: content
        ] [
            value: make object! [
                filename: copy tmp
                type: copy p-ct-type
                content: either none? p-content [none][copy p-content]
            ]
        ]
        either val-p: find list name
            [change/only next val-p compose [(first next val-p) (value)]]
            [append list compose [(to-set-word name) (value)]]
    ]
    use [ct-dispo ct-type content] [
        parse/all p-post-data [some mime-part "--" crlf]
    ]
    list
]

; After the following line, "probe cgi-object" will display all parts of
; the submitted multipart object:

cgi-object: construct decode-multipart-form-data 
    system/options/cgi/content-type copy submitted

; Write file to server using the original filename, and notify the user:

the-file: last split-path to-file copy cgi-object/photo/filename
write/binary the-file cgi-object/photo/content
print {
    <strong>UPLOAD COMPLETE</strong><br><br>
    <strong>Files currently in this folder:</strong><br><br>
}
folder: sort read %.
foreach file folder [
    print [rejoin [{<a href="./} file {">} file {</a><br>}]]
]
print {<br></td></tr></table></BODY></HTML>}

; Alternatively, you could forward to a different page when done:
; 
; wait 3
; refresh-me: {
;     <head><title></title>
;     <META HTTP-EQUIV="REFRESH" CONTENT="0; URL=./index.cgi"></head>
; }
; print refresh-me

This variation of the upload script allows you to select the directory to which files are uploaded:

#! /home/path/public_html/rebol/rebol -cs
REBOL [Title: "HTTP File Upload"]
print {content-type: text/html^/}
print {<HTML><HEAD><TITLE>File Upload</TITLE></HEAD>}
print {<BODY><br><br><center><table width=95% border=1>}
print {<tr><td width=100%><br><center>}

read-cgi: func [/local data buffer][
    switch system/options/cgi/request-method [
        "POST" [
            data: make string! 1020
            buffer: make string! 16380
            while [positive? read-io system/ports/input buffer 16380][
                append data buffer
                clear buffer
            ]
        ]
        "GET" [data: system/options/cgi/query-string]
    ]
    data
]

submitted: read-cgi

if submitted/2 = none [
    print {
        <FORM ACTION="./upload.cgi" 
        METHOD="post" ENCTYPE="multipart/form-data">
            <strong>Upload File:</strong><br><br> 
            <INPUT TYPE="file" NAME="photo"> <br><br>
            <INPUT TYPE="text" NAME="path" SIZE="35" 
                VALUE="/home/path/public_html/">
            <INPUT TYPE="submit" NAME="Submit" VALUE="Upload">  
        </FORM>
        <br></center></td></tr></table></BODY></HTML>
    }
    quit
]

decode-multipart-form-data: func [
    p-content-type
    p-post-data
    /local list ct bd delim-beg delim-end non-cr non-lf non-crlf mime-part
] [
    list: copy []
    if not found? find p-content-type "multipart/form-data" [return list]
    ct: copy p-content-type
    bd: join "--" copy find/tail ct "boundary="
    delim-beg: join bd crlf
    delim-end: join crlf bd
    non-cr:     complement charset reduce [ cr ]
    non-lf:     complement charset reduce [ newline ]
    non-crlf:   [ non-cr | cr non-lf ]
    mime-part:  [
        ( ct-dispo: content: none ct-type: "text/plain" )
        delim-beg ; mime-part start delimiter
        "content-disposition: " copy ct-dispo any non-crlf crlf
        opt [ "content-type: " copy ct-type any non-crlf crlf ]
        crlf ; content delimiter
        copy content
        to delim-end crlf ; mime-part end delimiter
        ( handle-mime-part ct-dispo ct-type content )
    ]
    handle-mime-part: func [
        p-ct-dispo
        p-ct-type
        p-content
        /local tmp name value val-p
    ] [
        p-ct-dispo: parse p-ct-dispo {;="}
        name: to-set-word (select p-ct-dispo "name")
        either (none? tmp: select p-ct-dispo "filename")
               and (found? find p-ct-type "text/plain") [
            value: content
        ] [
            value: make object! [
                filename: copy tmp
                type: copy p-ct-type
                content: either none? p-content [none][copy p-content]
            ]
        ]
        either val-p: find list name
            [change/only next val-p compose [(first next val-p) (value)]]
            [append list compose [(to-set-word name) (value)]]
    ]
    use [ct-dispo ct-type content] [
        parse/all p-post-data [some mime-part "--" crlf]
    ]
    list
]

cgi-object: construct decode-multipart-form-data 
    system/options/cgi/content-type copy submitted

the-file: last split-path to-file copy cgi-object/photo/filename
write/binary the-file cgi-object/photo/content
print {
    <strong>UPLOAD COMPLETE</strong><br><br>
    <strong>Files currently in this folder:</strong><br><br>
}
folder: sort read to-file cgi-object/path
current-folder: rejoin  at 
foreach file folder [
    print [rejoin [
        {<a href="http://site.com/"} (at cgi-object/path 28) file {">}
        ; convert path to URL
        file "</a><br>"
    ]]
]
print {<br></td></tr></table></BODY></HTML>}

15.11 File Downloader

Here's a script that demonstrates how to push download a file to the user's browser:

#!/home/path/public_html/rebol/rebol -cs
REBOL []
submitted: decode-cgi system/options/cgi/query-string
root-path: "/home/path"

; if no data has been submitted, request file name:

if ((submitted/2 = none) or (submitted/4 = none)) [
    print "content-type: text/html^/"
    print [<STRONG>"W A R N I N G  -  "]
    print ["Private Server, Login Required:"</STRONG><BR><BR>]
    print [<FORM ACTION="./download.cgi">]
    print [" Username: " <INPUT TYPE=text SIZE="50" NAME="name"><BR><BR>]
    print [" Password: " <INPUT TYPE=text SIZE="50" NAME="pass"><BR><BR>]
    print [" File: "<BR><BR>]
    print [<INPUT TYPE=text SIZE="50" NAME="file" VALUE="/public_html/">]
    print [<BR><BR>]
    print [<INPUT TYPE="SUBMIT" NAME="Submit" VALUE="Submit">]
    print [</FORM>]
    quit
]

; check user/pass, end program if incorrect:

username: submitted/2 password: submitted/4 
either (username = "user") and (password = "pass) [
    ; if user/pass is ok, go on
][
    print "content-type: text/html^/"
    print "Incorrect Username/Password." quit
]

print rejoin [
    "Content-Type: application/x-unknown"
    newline
    "Content-Length: "
    (size? to-file join root-path submitted/6) 
    newline
    "Content-Disposition: attachment; filename=" 
    (second split-path to-file submitted/6)
    newline
]

data: read/binary to-file join root-path submitted/6
data-length: size? to-file join root-path submitted/6
write-io system/ports/output data data-length

15.12 A Complete Web Server Management Application

This final script makes use of several previous examples, and some additional code, to form a complete web server management application. It allows you to list directory contents, upload, download, edit, and search for files, execute OS commands (chmod, ls, mv, cp, etc. - any command available on your web server's operating system), and run REBOL commands directly on your server. Edited files are automatically backed up into an "edit_history" folder on the server before being saved. No configuration is required for most web servers. Just save this script as "web-tool.cgi", upload it and the REBOL interpreter into the same folder as your web site's index.html file, set permissions (chmod) to 755, then go to http://yourwebsite/web-tool.cgi.

THIS SCRIPT CAN POSE A MAJOR SECURITY THREAT TO YOUR SERVER. It can potentially enable anyone to gain control of your web server and everything it contains. DO NOT install it on your server if you're at all concerned about security, or if you don't know how to secure your server yourself.

The first line of this script must point to the location of the REBOL interpreter on your web server, and you must use a version of REBOL which supports the "call" function (version 2.76 is recommended). By default, the REBOL interpreter should be uploaded to the same path as this script, that folder should be publicly accessible, and you must upload the correct version of REBOL for the operating system on which your server runs. IN THIS EXAMPLE, THE REBOL INTERPRETER HAS BEEN RENAMED "REBOL276".

#! ./rebol276 -cs
REBOL [Title: "REBOL CGI Web Site Manager"]

;-------------------------------------------------------------------------
; Upload this script to the same path as index.html on your server, then
; upload the REBOL interpreter to the path above (the same path as the
; script, by default).  CHMOD IT AND THIS SCRIPT TO 755.  Then, to run the
; program, go to www.yoursite.com/this-script.cgi .
;-------------------------------------------------------------------------

; YOU CAN EDIT THESE VARIABLES, _IF_ NECESSARY (change the quoted values):

; The user name you want to use to log in:

    set-username:   "username"

; The password you want to use to log in:

    set-password:   "password"

;-------------------------------------------------------------------------

; Do NOT edit these variables, unless you really know what you're doing:

doc-path: to-string what-dir
script-subfolder: find/match what-dir doc-path
if script-subfolder = none [script-subfolder: ""]

;-------------------------------------------------------------------------

; Get submitted data:

selection: decode-cgi system/options/cgi/query-string

read-cgi: func [/local data buffer][
    switch system/options/cgi/request-method [
        "POST" [
            data: make string! 1020
            buffer: make string! 16380
            while [positive? read-io system/ports/input buffer 16380][
                append data buffer
                clear buffer
            ]
        ]
        "GET" [data: system/options/cgi/query-string]
    ]
    the-data: data
    data
]
submitted: read-cgi
submitted-block: decode-cgi the-data

; ------------------------------------------------------------------------

; This section should be first because it prints a different header
; for a push download (not "content-type: text/html^/"):

if selection/2 = "download-confirm" [
    print rejoin [
        "Content-Type: application/x-unknown"
        newline
        "Content-Length: "
        (size? to-file selection/4) 
        newline
        "Content-Disposition: attachment; filename=" 
        (second split-path to-file selection/4)
        newline
    ]

    data: read/binary to-file selection/4
    data-length: size? to-file selection/4
    write-io system/ports/output data data-length
    quit
]

;-------------------------------------------------------------------------

; Print the normal HTML headers, for use by the rest of the script:

print "content-type: text/html^/"
print {<HTML><HEAD><TITLE>Web Site Manager</TITLE></HEAD><BODY>}

;-------------------------------------------------------------------------

; If search has been called (via link on main form):

if selection/2 = "confirm-search" [
    print rejoin [
        {<center><a href="./} 
        (second split-path system/options/script) {?name=} set-username
        {&pass=} set-password {">Back to Web Site Manager</a></center>}
    ]
    print {<center><table border="1" cellpadding="10" width=80%><tr><td>}
    print [<CENTER><TABLE><TR><TD>]
    print rejoin [
        {<FORM ACTION="./} (second split-path system/options/script) 
        {"> Text to search for: <BR> <INPUT TYPE="TEXT" SIZE="50"}
        {NAME="phrase"><BR><BR>Folder to search in: <BR>}
        {<INPUT TYPE="TEXT" SIZE="50" NAME="folder" VALUE="} what-dir
        {" ><BR><BR><INPUT TYPE=hidden NAME=perform-search }
        {VALUE="perform-search"><INPUT TYPE="SUBMIT" NAME="Submit" }
        {VALUE="Submit"></FORM></TD></TR></TABLE></CENTER>}
        {</td></tr></table></center></BODY></HTML>}
    ]
    quit
]

;-------------------------------------------------------------------------

; If edited file text has been submitted:

if submitted-block/2 = "save" [

    ; Save newly edited document:
    write (to-file submitted-block/6) submitted-block/4
    print {<center><strong>Document Saved:</strong>
        <br><br><table border="1" width=80% cellpadding="10"><tr><td>}
    prin [<center><textarea cols="100" rows="15" name="contents">]
    prin replace/all read (
        to-file (replace/all submitted-block/6 "%2F" "/")
    ) "</textarea>" "<\/textarea>"
    print [</textarea></center>]
    print rejoin [
        {</td></tr></table><br><a href="./} 
        (second split-path system/options/script) {?name=} set-username
        {&pass=} set-password {">Back to Web Site Manager</a></center>}
        {</BODY></HTML>}
    ]
    quit
]

;-------------------------------------------------------------------------

; If upload link has been clicked, print file upload form:

if selection/2 = "upload-confirm" [
    print rejoin [
        {<center><a href="./} 
        (second split-path system/options/script) {?name=} set-username
        {&pass=} set-password {">Back to Web Site Manager</a></center>}
    ]
    print {<center><table border="1" cellpadding="10" width=80%><tr><td>}
    print {<center>}

    ; If just the link was clicked - no data submitted yet:

    if selection/4 = none [
        print rejoin [
            {<FORM ACTION="./} (second split-path system/options/script)
            {" METHOD="post" ENCTYPE="multipart/form-data">
                <strong>Upload File:</strong><br><br> 
                <INPUT TYPE=hidden NAME=upload-confirm 
                VALUE="upload-confirm">
                <INPUT TYPE="file" NAME="photo"> <br><br>
                Folder: <INPUT TYPE="text" NAME="path" SIZE="35" 
                    VALUE="} what-dir {"> 
                <INPUT TYPE="submit" NAME="Submit" VALUE="Upload">  
            </FORM>
            <br></center></td></tr></table></center></BODY></HTML>}
        ]
        quit
    ]
]

;-------------------------------------------------------------------------

; If upload data has been submitted:

if (submitted/2 = #"-") and (submitted/4 = #"-") [

    ; This function is by Andreas Bolka:

    decode-multipart-form-data: func [
        p-content-type
        p-post-data
        /local list ct bd delim-beg delim-end non-cr
        non-lf non-crlf mime-part
    ] [
        list: copy []
        if not found? find p-content-type "multipart/form-data" [
            return list
        ]
        ct: copy p-content-type
        bd: join "--" copy find/tail ct "boundary="
        delim-beg: join bd crlf
        delim-end: join crlf bd
        non-cr:     complement charset reduce [ cr ]
        non-lf:     complement charset reduce [ newline ]
        non-crlf:   [ non-cr | cr non-lf ]
        mime-part:  [
            ( ct-dispo: content: none ct-type: "text/plain" )
            delim-beg ; mime-part start delimiter
            "content-disposition: " copy ct-dispo any non-crlf crlf
            opt [ "content-type: " copy ct-type any non-crlf crlf ]
            crlf ; content delimiter
            copy content
            to delim-end crlf ; mime-part end delimiter
            ( handle-mime-part ct-dispo ct-type content )
        ]
        handle-mime-part: func [
            p-ct-dispo
            p-ct-type
            p-content
            /local tmp name value val-p
        ] [
            p-ct-dispo: parse p-ct-dispo {;="}
            name: to-set-word (select p-ct-dispo "name")
            either (none? tmp: select p-ct-dispo "filename")
                   and (found? find p-ct-type "text/plain") [
                value: content
            ] [
                value: make object! [
                    filename: copy tmp
                    type: copy p-ct-type
                    content: either none? p-content [none][copy p-content]
                ]
            ]
            either val-p: find list name
                [
                    change/only next val-p compose [
                        (first next val-p) (value)
                    ]
                ]
                [append list compose [(to-set-word name) (value)]]
        ]
        use [ct-dispo ct-type content] [
            parse/all p-post-data [some mime-part "--" crlf]
        ]
        list
    ]

    ; After the following line, "probe cgi-object" will display all parts
    ; of the submitted multipart object:

    cgi-object: construct decode-multipart-form-data 
        system/options/cgi/content-type copy submitted

    ; Write file to server using the original filename, and notify the
    ; user:

    the-file: last split-path to-file copy cgi-object/photo/filename
    write/binary 
        to-file join cgi-object/path the-file 
        cgi-object/photo/content
    print rejoin [
        {<center><a href="./} 
        (second split-path system/options/script) {?name=} set-username
        {&pass=} set-password {">Back to Web Site Manager</a></center>}
    ]
    print {
        <center><table border="1" width=80% cellpadding="10"><tr><td>
        <strong>UPLOAD COMPLETE</strong><br><br></center>
        <strong>Files currently in this folder:</strong><br><br>
    }
    change-dir to-file cgi-object/path
    folder: sort read what-dir
    foreach file folder [
        print [
            rejoin [
                {<a href="./} (second split-path system/options/script)
                {?editor-confirm=editor-confirm&thefile=} 
                what-dir file {">(edit)</a>  }
                {<a href="./} (second split-path system/options/script)
                {?download-confirm=download-confirm&thefile=}
                what-dir file {">} "(download)</a>  " 
                {<a href="./} (find/match what-dir doc-path) file 
                {">} file {</a><br>}
            ]
        ]
    ]
    print {</td></tr></table></center></BODY></HTML>}
    quit
]

;-------------------------------------------------------------------------

; If no data has been submitted, print form to request user/pass:

if ((selection/2 = none) or (selection/4 = none)) [
    print rejoin [{
        <STRONG>W A R N I N G  -  Private Server, Login Required:</STRONG>
        <BR><BR>
        <FORM ACTION="./} (second split-path system/options/script) {">
        Username: <INPUT TYPE=text SIZE="50" NAME="name"><BR><BR>
        Password: <INPUT TYPE=text SIZE="50" NAME="pass"><BR><BR>
        <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="Submit">
        </FORM></BODY></HTML>
    }]
    quit
]

;-------------------------------------------------------------------------

; If a folder name has been submitted, print file list:

if ((selection/2 = "command-submitted") and (
    selection/4 = "call {^/^/^/^/}")
) [
    print rejoin [
        {<center><a href="./} 
        (second split-path system/options/script) {?name=} set-username
        {&pass=} set-password {">Back to Web Site Manager</a></center>}
    ]
    print {<center><table border="1" cellpadding="10" width=80%><tr><td>}
    print {<strong>Files currently in this folder:</strong><br><br>}
    change-dir to-file selection/6
    folder: sort read what-dir
    foreach file folder [
        print rejoin [
            {<a href="./} (second split-path system/options/script)
            {?editor-confirm=editor-confirm&thefile=}
            what-dir file {">} "(edit)</a>  " 
            {<a href="./} (second split-path system/options/script)
            {?download-confirm=download-confirm&thefile=}
            what-dir file {">} "(download)</a>  " 
            {<a href="./} (find/match what-dir doc-path) file {">} file
            {</a><br>}
        ]
    ]
    print {</td></tr></table></center></BODY></HTML>}
    quit
]

;-------------------------------------------------------------------------

; If editor has been called (via a constructed link):

if selection/2 = "editor-confirm" [

    ; backup (before changes are made):

    cur-time: to-string replace/all to-string now/time ":" "-"
    document_text: read to-file selection/4
    if not exists? to-file rejoin [
        doc-path script-subfolder "edit_history/"
    ] [
        make-dir to-file rejoin [
            doc-path script-subfolder "edit_history/"
        ]
    ]
    write to-file rejoin [
        doc-path script-subfolder "edit_history/" 
        to-string (second split-path to-file selection/4)
        "--" now/date "_" cur-time ".txt"
    ] document_text

    ; note the POST method in the HTML form:

    print rejoin [
        {<center><strong>Be sure to SUBMIT when done:</strong>}
        {<BR><BR><FORM method="post" ACTION="./} 
        (second split-path system/options/script) {">}
        {<INPUT TYPE=hidden NAME=submit_confirm VALUE="save">}
        {<textarea cols="100" rows="15" name="contents">}
        (replace/all document_text "</textarea>" "<\/textarea>")
        {</textarea><BR><BR><INPUT TYPE=hidden NAME=path VALUE="}
        selection/4
        {"><INPUT TYPE="SUBMIT" NAME="Submit" VALUE="Submit">
        </FORM></center></BODY></HTML>}
    ]
    quit
]

;-------------------------------------------------------------------------

; If search criteria has been entered:

if selection/6 = "perform-search" [
    phrase: selection/2
    start-folder: to-file selection/4
    change-dir start-folder
    ; found-list: ""

    recurse: func [current-folder] [ 
        foreach item (read current-folder) [ 
            if not dir? item [  
                if error? try [
                    if find (read to-file item) phrase [
                        print rejoin [
                            {<a href="./}
                            (second split-path system/options/script)
                            {?editor-confirm=editor-confirm&theitem=} 
                            what-dir item {">(edit)</a>  }
                            {<a href="./}
                            (second split-path system/options/script)
                            {?download-confirm=download-confirm&theitem=}
                            what-dir item {">(download)</a>  "}
                            phrase {" found in:  } 
                            {<a href="./} (find/match what-dir doc-path)
                            item {">} item {</a><BR>}
                        ]
                        ; found-list: rejoin [
                        ;     found-list newline what-dir item
                        ; ]
                    ] 
                ] [print rejoin ["error reading " item]]
            ]
        ]
        foreach item (read current-folder) [ 
            if dir? item [
                change-dir item 
                recurse %.\
                change-dir %..\
            ] 
        ]
    ]

    print rejoin [
        {<center><a href="./} 
        (second split-path system/options/script) {?name=} set-username
        {&pass=} set-password {">Back to Web Site Manager</a></center>}
    ]
    print {<center><table border="1" cellpadding="10" width=80%><tr><td>}
    print rejoin [
        {<strong>SEARCHING for "} phrase {" in } start-folder
        {</strong><BR><BR>}
    ]
    recurse %.\
    print {<BR><strong>DONE</strong><BR>}
    print {</td></tr></table></center></BODY></HTML>}
    ; save %found.txt found-list
    quit
]

;-------------------------------------------------------------------------

; This is the main entry form, used below:

entry-form: [
    print rejoin [
        {<CENTER><strong>current path: </strong>} what-dir 
        {<FORM METHOD="get" ACTION="./} 
        (second split-path system/options/script) {">}{<INPUT TYPE=hidden}
        { NAME=submit_confirm VALUE="command-submitted">}
        {<TEXTAREA COLS="100" ROWS="10" NAME="contents">}
        {call {^/^/^/^/}</textarea><BR><BR>}
        {List Files: <INPUT TYPE=text SIZE="35" NAME="name" VALUE="} 
        what-dir {"><INPUT TYPE="SUBMIT" NAME="Submit" VALUE="Submit">}
        {       <A HREF="./} (second split-path system/options/script)
        {?upload-confirm=upload-confirm">upload</A>     } ; leave spaces
        {<A HREF="./} (second split-path system/options/script)
        {?confirm-search=confirm-search">search</A>}
        {</FORM><BR></CENTER>}
    ]
]

;-------------------------------------------------------------------------

; If code has been submitted, print the output, along with an entry form):

if ((selection/2 = "command-submitted") and (
selection/4 <> "call {^/^/^/^/}") and ((to-file selection/6) = what-dir))[
    write %commands.txt join "REBOL[]^/" selection/4
    ; The "call" function requires REBOL version 2.76:
    call/output/error 
        "./rebol276 -qs commands.txt" 
        %conso.txt %conse.txt
    do entry-form
    print rejoin [
        {<CENTER>Output: <BR><BR>}
        {<TABLE WIDTH=80% BORDER="1" CELLPADDING="10"><TR><TD><PRE>}
        read %conso.txt
        {</PRE></TD></TR></TABLE><BR><BR>}
        {Errors: <BR><BR>}
        read %conse.txt
        {</CENTER></BODY></HTML>}
    ]
    quit
]
;-------------------------------------------------------------------------

if ((selection/2 = "command-submitted") and (
    selection/4 <> "call {^/^/^/^/}") and (
    (to-file selection/6) <> what-dir)
) [
    print rejoin [
        {<center><a href="./} 
        (second split-path system/options/script) {?name=} set-username
        {&pass=} set-password {">Back to Web Site Manager</a></center>}
    ]
    print {
        <center><table border="1" cellpadding="10" width=80%><tr><td>
            <center>
        You must EITHER enter a command, OR enter a file path to list.<BR>
        Please go back and try again (refresh the page if needed).
            </center>
        </td></tr></center></BODY></HTML>
    }
    quit
]

;-------------------------------------------------------------------------

; Otherwise, check submitted user/pass, then print form for code entry:

username: selection/2 password: selection/4 
either (username = set-username) and (password = set-password) [ 
    ; if user/pass is ok, go on
][
    print "Incorrect Username/Password. </BODY></HTML>" quit
]

do entry-form
print {</BODY></HTML>}

15.13 The RebolForum.com CGI Code

Here's the code for the forum CGI application at http://rebolforum.com. This is the actual code that runs the web site where you can go to ask questions about this tutorial. It's presented here in compressed format here so that the code fits nicely on this web page:

REBOL [title: "RebolForum.com"]  
editor decompress #{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17AD398AC141611906C99234AFE4CB0080813CA3E181A62D657995E2C612A654
16C1FAC5695414648CFFE0B008CB264C2BCDC5DB970D73BA8693EDEFBAC25CC7
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2A6EBB09B93D9D5AEFE90A0AFAE804D50BDB2F7EC072B7557C6F1551C5561155
3D5944ED812FB2779A0B94E71741B536E7736E7372B2CC5DEEEC0ACE9AFAA62E
453F57C22E4AD0DDEF7D9F7EE71B20EEDC22F41E88212C7172D69BC95A589075
DF1A8DFDC2018D903CE0E95A3432AD3FF3B92D7028B192FB5DC5D31F21A12B4F
128E47E0EAD0F5EE96AF44D76629BFD4A718ECAD8DAAF1E0D870C05EABE8F36A
280B53F47D8C221E235857255E0FEB9F48D1C4ABFE411444065A2868CC7ED0BD
750B7235732B28390DCE665D88339E7643CE0BEE35AD10B7DE0A1C88F204DBA4
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CA5162928FD88FC2C398350FA330CB2FD343DE1F3FBC527A9E6F2ACFA36475CC
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16E7940C4BB6877C6E777992864144D994C87590F81E1DEBD08D496B83CCF6AF
FF07541284A7EE410000
}

15.14 Etsy Account Manager

A complete tutorial about using REBOL with the Etsy API is available at http://re-bol.com/etsy_api_tutorial.html. This CGI program demonstrates how to access many of the Etsy API functions:

#! ../rebol276 -cs
REBOL [Title: "Etsy"]
print {content-type: text/html^/^/}
print {<HTML><HEAD><TITLE>Etsy</TITLE></HEAD><BODY>}
read-cgi: func [/local data buffer][
    switch system/options/cgi/request-method [
        "POST" [
            data: make string! 1020
            buffer: make string! 16380
            while [positive? read-io system/ports/input buffer 16380][
                append data buffer
                clear buffer
            ]
        ]
        "GET" [data: system/options/cgi/query-string]
    ]
    data
]
submitted: decode-cgi submitted-bin: read-cgi
if ((submitted/2 = none) or (submitted/4 = none)) [
    print {
        <STRONG>W A R N I N G  -  Private Server:</STRONG><BR><BR>
        <FORM METHOD="post" ACTION="./etsy.cgi">
            Username: <input type=text size="50" name="name"><BR><BR>
            Password: <input type=text size="50" name="pass"><BR><BR>
            <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="submit">
        </FORM>
        </BODY></HTML>
    } 
    quit
]
myusername: "some-user-name"  mypassword: "some-password"
username: submitted/2   password: submitted/4 
either ((username = myusername) and (password = mypassword)) [][
    print "Incorrect Username/Password." 
    print {</BODY></HTML>} quit
]
do-etsy: does [
    do/args http://reb4.me/r/etsy.r context [
    Consumer-Key: #<my-key>
    Consumer-Secret: #<my-secret>
    User-Store: %etsyusers
    Scope: [listings_w listings_r listings_d]
    Sandbox: true
    ] 
    etsy/as "<my-user-name>"
]
if submitted/6 = "sale" [
    do-etsy
    coupon-code: submitted/8
    add-or-remove: submitted/10
    print "FOUND ITEMS:<br><br>"
    found: copy []
    x: get in (etsy/listings []) 'results
    for i 1 (length? x) 1 [  
        print copy rejoin [
            (get in x/:i 'title) <br>
        ] 
        append found (get in x/:i 'listing_id)
        append found (get in x/:i 'description)
        append found (get in x/:i 'title)
        append found (get in x/:i 'state)
    ]
    print "<br><br>REPLACED ITEMS:<br><br>"
    foreach [lstngid dscrptn titl state] found [
        either state <> "active" [
            print copy rejoin [
                titl { was NOT replaced (listing inactive)<br>}
            ]
        ][
            etsy/api-call/with put rejoin [
                %listings/ lstngid
            ] either add-or-remove = "add" [
                [
                    title: rejoin ["SALE-" titl]
                    description: rejoin [coupon-code dscrptn]
                ]
            ] [
                [
                    title: replace titl "SALE-" ""
                    description: replace dscrptn rejoin [
                        coupon-code] ""
                ]
            ]
            print copy rejoin [titl {<br>}]
        ]
    ]
    print "<br>Done<br><br>"
    quit
]
if submitted/6 = "replace" [
    do-etsy
    search-text: submitted/8
    replace-text: submitted/10
    print "FOUND ITEMS:<br><br>"
    found: copy []
    x: get in (etsy/listings []) 'results              
    for i 1 (length? x) 1 [  
        if find (get in x/:i 'description) search-text [ 
            print rejoin [
                ; {"} search-text {" found in:  } 
                (get in x/:i 'title) "<br>"
            ] 
            append found (get in x/:i 'listing_id)
            append found (get in x/:i 'description)
            append found (get in x/:i 'title)
            append found (get in x/:i 'state)
        ]
    ]
    print "<br><br>REPLACED ITEMS:<br><br>"
    foreach [lstngid dscrptn titl state] found [
        either state <> "active" [
            print copy rejoin [
                titl { was NOT replaced (listing inactive)<br>}
            ]
        ][
            etsy/api-call/with put rejoin [
                %listings/ lstngid
            ] [
                description: (
                    replace/all dscrptn search-text replace-text
                )
            ]
            print copy rejoin [titl {<br>}]
        ]
    ]
    print "<br>Done<br><br>"
    quit
]
if submitted/6 = "create-listing" [
    do-etsy
    itm: submitted/8
    desc: submitted/10
    prc:  to-decimal next find submitted/12 "$"
    ctgry: submitted/14
    print "Creating item...<br><br>"
    etsy/api-call/with post %/listings [
        quantity: 1 
        title: itm 
        description: desc 
        price: prc 
        category_id: ctgry 
        who_made: "i_did" 
        is_supply: "1" 
        when_made: "2010_2012" 
        shipping_template_id: "330"
    ]
    print rejoin ["CREATED: " itm ", " desc ", " prc]
    quit
]
if submitted/6 = "delete-listing" [
    do-etsy
    itm2del: submitted/8
    print "Deleting...<br><br>"
    etsy/api-call/with get rejoin [%listings/ itm2del] [
        method: "DELETE"
    ]
    print rejoin ["Item " itm2del " deleted."]
    quit
]
if submitted/6 = "view-raw" [
    do-etsy
    print {<pre>}
    probe copy get in (etsy/listings []) 'results
    print {</pre>}
    quit
]
if submitted/6 = "get-image2" [
    do-etsy
    photo-item-id: submitted/8
    photo-list: etsy/api-call/with get rejoin [
        %listings/ photo-item-id "/images"
    ] []
    either error? try [photo-id: first get in photo-list 'results] [
        print "No photo available for that item."
        return
    ][
        photo-info: etsy/api-call/with get the-code: rejoin [
            %listings/ photo-item-id "/images/ " photo-id
        ] []
    ]
    probe either [] = the-photo: (get in photo-info 'results) [
        "none"
    ] [
        the-photo
    ]
    quit
]
default-coupon-code: {
    ** SALE ** Enter the coupon code &quot;982u3445&quot; at 
    checkout to receive 10% off your order.&lt;br&gt;&lt;br&gt;
}
print rejoin [
    {<h2>Add or Remove Sale:</h2>
    <FORM METHOD="post" ACTION="./etsy.cgi">
        <INPUT TYPE=hidden NAME="username" VALUE="} myusername {">
        <INPUT TYPE=hidden NAME="password" VALUE="} mypassword {">
        <INPUT TYPE=hidden NAME="subroutine" VALUE="sale">
        Coupon Code:<BR>
        <TEXTAREA COLS="50" ROWS="18" NAME="couponcode">}
            default-coupon-code 
        {</TEXTAREA><BR><BR>
        Add or Remove: <select NAME="addorremove">
            <option>add
            <option>remove
        </option></select><br><br>
        <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="submit">
    </FORM>
    <BR><HR>
    <h2>Replace In Description:</h2>
    <FORM METHOD="post" ACTION="./etsy.cgi">
        <INPUT TYPE=hidden NAME="username" VALUE="} myusername {">
        <INPUT TYPE=hidden NAME="password" VALUE="} mypassword {">
        <INPUT TYPE=hidden NAME="subroutine" VALUE="replace">
        Search Text:<BR><BR>
        <input type=text size="35" name="searchtext">
        <BR><BR>
        Replace Text:<BR><BR>
        <input type=text size="35" name="replacetext">
        <BR><BR>
        <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="submit">
    </FORM>
    <BR><HR>
    <h2>Create Listing:</h2>
    <FORM METHOD="post" ACTION="./etsy.cgi">
        <INPUT TYPE=hidden NAME="username" VALUE="} myusername {">
        <INPUT TYPE=hidden NAME="password" VALUE="} mypassword {">
        <INPUT TYPE=hidden NAME="subroutine" VALUE="create-listing">
        Title: <BR><BR>
        <input type=text size="35" name="title" value="Ring 100">
        <BR><BR>
        Description: <BR><BR>
        <input type=text size="35" name="description" 
            value="Ring 100.  A very pretty ring."><BR><BR>
        Price: <BR><BR>
        <input type=text size="35" name="Price" value="$19.99">
        <BR><BR>
        Category: <BR><BR>
        <input type=text size="35" name="Category" value="69150467">
        <BR><BR>
        <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="submit">
    </FORM> 
    <BR><HR>
    <h2>Delete Listing:</h2>
    <FORM METHOD="post" ACTION="./etsy.cgi">
        <INPUT TYPE=hidden NAME="username" VALUE="} myusername {">
        <INPUT TYPE=hidden NAME="password" VALUE="} mypassword {">
        <INPUT TYPE=hidden NAME="subroutine" VALUE="delete-listing">
        Listing ID #: <BR><BR>
        <input type=text size="35" name="listing-id"><BR><BR>
        <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="submit">
    </FORM> 
    <BR><HR>
    <h2>View All Raw Listing Data:</h2>
    <FORM METHOD="post" ACTION="./etsy.cgi">
        <INPUT TYPE=hidden NAME="username" VALUE="} myusername {">
        <INPUT TYPE=hidden NAME="password" VALUE="} mypassword {">
        <INPUT TYPE=hidden NAME="subroutine" VALUE="view-raw">
        <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="submit">
    </FORM> 
    <BR><HR>
    <h2>View Image:</h2>
    <FORM METHOD="post" ACTION="./etsy.cgi">
        <INPUT TYPE=hidden NAME="username" VALUE="} myusername {">
        <INPUT TYPE=hidden NAME="password" VALUE="} mypassword {">
        <INPUT TYPE=hidden NAME="subroutine" VALUE="view-image">
        <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="submit">
    </FORM> 
    </BODY></HTML>}
]
quit

For comparison, a GUI version of a program providing access to the same Etsy API functions is provided below:

REBOL [title: "Etsy"]
do/args http://reb4.me/r/etsy.r context [
    Consumer-Key: #<type_your_key_here>
    Consumer-Secret: #<typ_your_secret_here>
    User-Store: %etsyusers
    Scope: [listings_w listings_r listings_d]  ; edit permissions here
    Sandbox: false                      ; change to true when approved
]
coupon-text: {
    ** SALE ** Enter the coupon code &quot;893894&quot; at checkout to
    receive 10% off your order &lt;br&gt;&lt;br&gt;
}
replace-items: does [
    found-items/text: copy {}  show found-items
    replaced-items/text: copy {}  show replaced-items
    found: copy []
    x: get in (etsy/listings []) 'results              
    for i 1 (length? x) 1 [  
        if find (get in x/:i 'description) search-text/text [ 
            insert head found-items/text copy rejoin [
                ; {"} search-text/text {" found in:  } 
                (get in x/:i 'title) newline
            ] 
            show found-items
            append found (get in x/:i 'listing_id)
            append found (get in x/:i 'description)
            append found (get in x/:i 'title)
            append found (get in x/:i 'state)
        ]
    ]
    foreach [lstngid dscrptn titl state] found [
        either state <> "active" [
            insert head replaced-items/text copy rejoin [
                titl { was NOT replaced (listing inactive)^/}
            ]
            show replaced-items
        ][
            etsy/api-call/with put rejoin [
                %listings/ lstngid
            ] [
                description: (
                    replace/all dscrptn search-text/text replace-text/text
                )
            ]
            insert head replaced-items/text copy rejoin [titl {^/}]
            show replaced-items
        ]
    ]
    ; alert "Done"
]
sale: func [add-or-remove] [
    coupon-code: copy request-text/title/default"Coupon Text:" coupon-text
    found-items/text: copy {}  show found-items
    replaced-items/text: copy {}  show replaced-items
    found: copy []
    x: get in (etsy/listings []) 'results
    focus found-items           
    for i 1 (length? x) 1 [  
        insert head found-items/text copy rejoin [
            (get in x/:i 'title) newline
        ] 
        show found-items
        append found (get in x/:i 'listing_id)
        append found (get in x/:i 'description)
        append found (get in x/:i 'title)
        append found (get in x/:i 'state)
    ]
    foreach [lstngid dscrptn titl state] found [
        either state <> "active" [
            insert head replaced-items/text copy rejoin [
                titl { was NOT replaced (listing inactive)^/}
            ]
            show replaced-items
        ][
            etsy/api-call/with put rejoin [
                %listings/ lstngid
            ] either add-or-remove = true [
                [
                    title: rejoin ["SALE-" titl]
                    description: rejoin [coupon-code dscrptn]
                ]
            ] [
                [
                    title: replace titl "SALE-" ""
                    description: replace dscrptn rejoin [coupon-code] ""
                ]
            ]
            insert head replaced-items/text copy rejoin [titl {^/}]
            show replaced-items
        ]
    ]
    focus replaced-items
    ; alert "Done"
]
create-listing: does [
    itm: request-text/title/default "Title:" "Item 100"
    desc: request-text/title/default "Description:" "Ring #100"
    prc:  to-decimal next find (
            request-text/title/default "Price:" "$19.99"
            ) "$"
    if true = request "Would you like to see a listing of category IDs?" [
        categories: etsy/api-call get %taxonomy/categories
        cat-list: copy []
        foreach category categories/results [
            append cat-list reduce [
                category/long_name category/category_id
            ]
        ]
        chosen-category: request-list "Categories" cat-list
    ]
    if unset? chosen-category [chosen-category: "69150467"]
    ctgry: request-text/title/default "Category ID:" form chosen-category
    flash "Creating item..."
    etsy/api-call/with post %/listings [
        quantity: 1 
        title: itm 
        description: desc 
        price: prc 
        category_id: ctgry 
        who_made: "i_did" 
        is_supply: "1" 
        when_made: "2010_2012" 
        shipping_template_id: "330"
    ]
    unview
    alert rejoin ["CREATED: " itm ", " desc ", " prc]
]
delete-listing: does [
    itm2del: request-text/title "Listing ID #:"
    either true = request "Really Delete?" [
        flash "Deleting..."
        etsy/api-call/with get rejoin [%listings/ itm2del] [
            method: "DELETE"]
        unview
        alert rejoin ["Item " itm2del " deleted."]
    ] [
        return
    ]
]
get-image: does [
    found: copy []
    x: get in (etsy/listings []) 'results  
    for i 1 (length? x) 1 [  
        append found (get in x/:i 'title)
        append found (get in x/:i 'listing_id)
    ]
    photo-item-id: request-list "Select Item:" found
    photo-list: etsy/api-call/with get rejoin [
        %listings/ photo-item-id "/images"] []
    either error? try [photo-id: first get in photo-list 'results] [
        alert "No photo available for that item."
        return
    ][
        photo-info: etsy/api-call/with get the-code: rejoin [
            %listings/ photo-item-id "/images/ " photo-id
        ] []
    ]
    editor either [] = the-photo: (get in photo-info 'results) [
        "none"
    ] [
        the-photo
    ]
]
etsy/as "<your-username>"
view center-face gui: layout [
    across
    text 80 right "If" 
    cond1: drop-down 100 data [
        "Title" "Description" "Listing ID" "Any Field"
    ]
    cond2: drop-down 150 data [
        "REPLACE ALL" "Contains" "Does NOT Contain" "Equals"
    ]
    cond3: field 454 "ring" return
    text 80 right "Search Text:" search-text: field 720 "ring" [
        replace-text/text: copy search-text/text show replace-text
    ] return
    text 80 right "Replace Text:" replace-text: field 720 "ring" return
    text 805 "" return
    box black 805x2 return
    text 805 "" return
    text 400 "Found Items:" text 200 "Replaced Items:" return
    found-items: area  replaced-items: area  return
    btn "List Raw Data" [editor copy get in (etsy/listings []) 'results]
    btn "Create Listing" [create-listing]
    btn "Delete Listing" [delete-listing]
    btn "Add Sale" [sale true]
    btn "Remove Sale" [sale false]
    btn "View Image" [get-image]
    btn "Replace Description" [replace-items]
]

Be sure to see the following links for more insight about REBOL CGI programming:

http://re-bol.com/cgi_tutorial.txt
http://rebol.com/docs/cgi1.html
http://rebol.com/docs/cgi2.html
http://rebol.com/docs/cgi-bbs.html
http://www.rebol.net/cookbook/recipes/0045.html

To create web sites using a PHP-like version of REBOL that runs in a web server written entirely in REBOL, see:

http://cheyenne-server.org (binaries are available for Windows, Mac, and Linux).
http://cheyenne-server.org/docs/rsp-api.html - documentation for the "RSP" (REBOL server pages) API.

15.15 A Note About Working With Web Servers

To do any work with your web server, you'll need to know your account's FTP username, password, URL, and publicly viewable root folder. Be sure to have that info on hand before trying to accomplish any CGI programming.

The most common interface for managing web sites hosted by popular companies is a piece of software called "cPanel". Instructions for accessing and using cPanel are available all around the Internet, and will most likely be emailed by your hosting company. This author recommends lunarpages.com and hostgator.com, and those two companies are known to support REBOL CGI programming.

To begin building a web application with REBOL, you'll need to upload the REBOL interpreter to your web server. You only need to do this once for each web server (not for each program). If you do not have access to cPanel or some other web based file manager, you can use REBOL to manage the entire server setup, and all script editing, and file management operations. To upload REBOL to your server, open your local REBOL interpreter console and type the following code, but REPLACE the username, password, URL, and publicly viewable folder with your own account info. This will download a REBOL interpreter from the web, and upload it to your own server:

file: ftp://user:pass@site.com/public_html/rebol ; EDIT with your info
write/binary file (read/binary http://re-bol.com/rebol276)

The file transfer process above should take just a few seconds if you're on a broadband connection. Once it's done, you need to set execute "permissions" for the REBOL interpreter in your hosting account. You can use the following REBOL script to do that. Just paste this code into your local REBOL interpreter and enter your web server URL, username, password, folder, etc., when prompted:

REBOL [title: "FTP CHMOD"]
website: request-text/title/default "Web Site:" "site.com"
username: request-text/title/default "User Name:" "user"
password: request-text/title/default "Password:" "pass"
folder: request-text/title/default "Folder:" "public_html"
file: request-text/title/default "File:" "rebol"
permission: request-text/title/default "Permission:" "755"
write %ftpargs.txt trim rejoin [{
    open } website {
    user } username { } password {
    cd } folder {
    literal chmod } permission { } file {
    quit
}]
call/show "ftp -n -s:ftpargs.txt"

If you have any problems using the above program on your operating system, you can simply run your OS's command line FTP program using the code below, and manually enter your web host account information as described:

call/show {ftp}   ; run this line in the REBOL interpreter console

; Type the following command at the FTP prompt (replace your web url):

open yourdomain.com  ; enter your username and password when prompted

; Type the following commands (replace your folder and file names):

cd public_html/
literal chmod 755 rebol
quit

All the steps above only need to be completed the very first time you set up your web hosting account. Once you've got REBOL uploaded to your server, you can begin to create your first CGI program. To start editing a new web site script, type the following into your local REBOL interpreter console (again, be sure to edit the user name, password, URL, and public folder information to match your web server account settings):

editor ftp://user:pass@site.com/public_html/example.cgi ; EDIT account

Type the following code into the REBOL text editor and save it (clicking "Save" in the REBOL text editor ACTUALLY SAVES/UPLOADS THE CHANGES TO YOUR WEB SERVER):

#!./rebol -cs
REBOL []
print {content-type: text/html^/}

Run the "FTP CHMOD" program above one more time to set the permissions for this new "example.cgi" to 755 (you'll need to set permissions to 755 for every .cgi script you create and upload to your server, so keep the above script handy). To be clear, in the ftp script above, change "rebol" to "example.cgi". Now browse to http://yourdomain.com/example.cgi , and you will see a blank page (replace "yourdomain.com" in the URL to the domain of your actual web server). If you get any errors, see the highlighted instructions below about error logs in cPanel.

15.16 WAP - Cell Phone Browser CGI Apps (deprecated)

NOTE: This section has been mostly deprecated by modern phone technology, but it's included here for potential usefulness, and to provide futher material in the study of CGI coding.

Most cell phone service providers offer data options which allow users to access information on the Internet. If you use a "smart phone", your data package likely allows you to access normal web pages using a browser program that runs on your phone (with varying degrees of rendering success). "Dumb" cell phones, however, come only with a "WAP" browser that allows you to access only very light mobile versions of web sites, and provides information in a format specifically accessible only by cell phones. Using WAP mobile sites, you can check email in Google, Yahoo, and other accounts, read news, get weather and traffic reports, manage Ebay transactions, etc. WAP versions of sites, accessible on normal cell phones are not renditions of the normal HTML sites created or interpreted by your phone, but are instead entirely separate versions of each site, created and managed on the web server by the web site creators, and simply accessed by WAP phone browsers.

You can create your own WAP CGI applications, to be accessed by any phone with a WAP browser, using REBOL. WAP scripts are just as easy to ceate as normal CGI web scripts. Instead of HTML, however, you simply need to format the output of your scripts using WAP ("Wireless Application Protocal") syntax. Reference information about WAP tags ("WML") can be found at http://www.w3schools.com/WAP/wml_reference.asp

Here's a basic WAP CGI script which demonstrates the stock code required in all your REBOL WAP scripts. The first 5 lines should be memorized. You'll need to copy them verbatim to the beginning of every WAP script you create. The last lines demonstrate some other important WAP tags. Notice that the wml tag basically replaces the html tag from normal HTML. Every WAP page also contains card tags, which basically replace the head and body tags in normal HTML. This script prints the current time in a WAP browser. Remember to set the permissions of (chmod) any WAP CGI script to 755:

#!./rebol276 -cs
REBOL []
prin {Content-type: text/vnd.wap.wml^/^/}
prin {<?xml version="1.0" encoding="iso-8859-1"?>^/}
prin {<!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.1//EN"
"http://www.wapforum.org/DTD/wml_1.1.xml">^/}

; The lines above are standard headers for any WAP CGI script.  The
; lines below print out the standard tags needed to print text on a
; WAP page.  Included inside the wml, card and p (paragraph) tags is
; one line that prints the current time:

print {<wml><card id="1" title="Current Time"><p>}
print now
print {</p></card></wml>}
quit

The following nearly identical script converts text data output by another script on the web site to WAP format, so that it can be read on small cell phone browsers. Because WAP syntax is a bit more strict than HTML, some HTML tags must be removed (replaced) from the source script output. You must be careful to strip out unnecessary tags and characters in text formatted for display in cell phones. Most WAP browsers will simply display an error if they encounter improperly formatted content:

#!./rebol276 -cs
REBOL []
prin {Content-type: text/vnd.wap.wml^/^/}
prin {<?xml version="1.0" encoding="iso-8859-1"?>^/}
prin {<!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.1//EN"
"http://www.wapforum.org/DTD/wml_1.1.xml">^/}

print {<wml><card id="1" title="Wap Page"><p>}
prin replace/all (read http://site.com/page.cgi) {</BODY> </HTML>} {}
print {</p></card></wml>}
quit

Here's a bit more useful version of the above script which allows users to specify the file to be converted, right in the URL of WAP page (i.e., if this script is at site.com/wap.cgi, and the user wants to read page.txt in their WAP browser, then the URL would be "http://site.com/wap.cgi?page.txt"):

#!./rebol276 -cs
REBOL []
submitted: decode-cgi system/options/cgi/query-string
prin {Content-type: text/vnd.wap.wml^/^/}
prin {<?xml version="1.0" encoding="iso-8859-1"?>^/}
prin {<!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.1//EN"
"http://www.wapforum.org/DTD/wml_1.1.xml">^/}
print {<wml><card id="1" title="Wap Page"><p>}

; The line below joins the web site URL with the submitted page,
; reads it, and parses it, up to some indicated marker text, so
; that only the text before the marker text is displayed:

parse read join http://site.com/ submitted/2 [
    thru submitted/2 copy p to "some marker text"
]
prin p

print {</p></card></wml>}
quit

Here's a version of the above script that lets users select a document to be converted and displayed. This code makes use of select and option tags, which work like HTML dropdown boxes in forms. It also demonstrates how to use anchor, go and postfield tags to submit form data. These work like the "action" in HTML forms. Variable labels for information entered by the user are preceded by a dollar symbol ("$"), and the variable name is enclosed in parentheses (i.e., the $(doc) variable below is submitted to the wap.cgi program). The anchor tag creates a clickable link that makes the action occur:

#!./rebol -cs
REBOL []
submitted: decode-cgi system/options/cgi/query-string
prin {Content-type: text/vnd.wap.wml^/^/}
prin {<?xml version="1.0" encoding="iso-8859-1"?>^/}
prin {<!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.1//EN"
"http://www.wapforum.org/DTD/wml_1.1.xml">^/}

; If no data has been submitted, do this by default:

if submitted/2 = none [

    ; Print some standard tags: 

    print {<wml><card id="1" title="Select Doc"><p>}

    ; Get a list of subfolders and display them in a dropdown box:

    folders: copy []
    foreach folder read %./docs/ [
        if find to-string folder {/} [append folders to-string folder]
    ]
    print {Doc: <select name="doc">}
    foreach folder folders [
        folder: replace/all folder {/} {}
        print rejoin [{<option value="} folder {">} folder {</option>}]
    ]
    print {</select>

    ; Create a link to submit the chosen folder, then close the tags
    ; from above:

    <anchor>
       <go method="get" href="wap.cgi">
           <postfield name="doc" value="$(doc)"/>
       </go>
       Submit
    </anchor>}
    print {</p></card></wml>}
    quit
]

; If some data has been submitted, read the selected doc:

print rejoin [{<wml><card id="1" title="} submitted/2 {"><p>}]

parse read join http://site.com/docs/ submitted/2 [
    thru submitted/2 copy p to "end of file"
]
prin p

print {</p></card></wml>}
quit

This script breaks up the selected text document into small (130 byte) chunks so that it can be navigated more quickly. Each separate card is displayed as a different page in the WAP browswer, and anchor links are provided to navigate forward and backword between the cards. For the user, paging through data in this way tends to be much faster than scrolling through long results line by line:

#!./rebol276 -cs
REBOL []
submitted: decode-cgi system/options/cgi/query-string
prin {Content-type: text/vnd.wap.wml^/^/}
prin {<?xml version="1.0" encoding="iso-8859-1"?>^/}
prin {<!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.1//EN"
"http://www.wapforum.org/DTD/wml_1.1.xml">^/}

count: 0
p: read http://site.com/folder.txt 
print {<wml>}
forskip p 130 [

    ; Create a counter, to appear as each card title, then print links
    ; to go forward and backward between the cards:

    count: count + 1
    print rejoin [{<card id="} count {" title="page-} count {"><p>}]
    print rejoin [
        {<anchor>Next<go href="#} (count + 1) {"/></anchor>}
    ]
    print rejoin [{<anchor>Back<prev/></anchor>}]

    ; Print 130 characters in each card:

    print copy/part p 130
    print {</p></card>}
]
print {</wml>}
quit

This next script combines the techniques explained so far, and allows the user to select a file on the web server, using a dropdown box, and displays the selected file in 130 byte pages:

#!./rebol276 -cs
REBOL []
submitted: decode-cgi system/options/cgi/query-string
prin {Content-type: text/vnd.wap.wml^/^/}
prin {<?xml version="1.0" encoding="iso-8859-1"?>^/}
prin {<!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.1//EN"
"http://www.wapforum.org/DTD/wml_1.1.xml">^/}

if submitted/2 = none [   
    print {<wml><card id="1" title="Select Teacher"><p>}
    ; print {Name: <input name="name" size="12"/>}
    folders: copy []
    foreach folder read %./Teachers/ [
        if find to-string folder {/} [append folders to-string folder]
    ]
    print {Teacher: <select name="teacher">}
    foreach folder folders [
        folder: replace/all folder {/} {}
        print rejoin [
            {<option value="} folder {">} folder {</option>}
        ]
    ]
    print {</select>
    <anchor>
       <go method="get" href="wap.cgi">
           <postfield name="teacher" value="$(teacher)"/>
       </go>
       Submit
    </anchor>}
    print {</p></card></wml>}
    quit
]

count: 0
parse read join http://site.com/folder/ submitted/2 [
    thru submitted/2 copy p to "past students"
]
print {<wml>}

forskip p 130 [
    count: count + 1
    print rejoin [
        {<card id="} count {" title="} submitted/2 "-" count {"><p>}
    ]
    print rejoin [
        {<anchor>Next<go href="#} (count + 1) {"/></anchor>}
    ]
    print rejoin [{<anchor>Back<prev/></anchor>}]
    print copy/part p 130
    print {</p></card>}
]
print {</wml>}
quit

Finally, this script allows users to select a file, and enter some text to be saved in that file, using the input tag:

#!./rebol276 -cs
REBOL []
submitted: decode-cgi system/options/cgi/query-string
prin {Content-type: text/vnd.wap.wml^/^/}
prin {<?xml version="1.0" encoding="iso-8859-1"?>^/}
prin {<!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.1//EN"
"http://www.wapforum.org/DTD/wml_1.1.xml">^/}

if submitted/2 = none [   
    print {<wml><card id="1" title="Select Teacher"><p>}
    print {Insert Text: <input name="thetext" size="12"/>}
    folders: copy []
    foreach folder read %./Teachers/ [
        if find to-string folder {/} [
            append folders to-string folder
        ]
    ]
    print {Teacher: <select name="teacher">}
    foreach folder folders [
        folder: replace/all folder {/} {}
        print rejoin [
            {<option value="} folder {">} folder {</option>}
        ]
    ]
    print {</select>
    <anchor>
       <go method="get" href="wapinsert.cgi">
           <postfield name="teacher" value="$(teacher)"/>
           <postfield name="thetext" value="$(thetext)"/>
       </go>
       Submit
    </anchor>}
    print {</p></card></wml>}
    quit
]

chosen-file: rejoin [%./Teachers/ submitted/2 "/schedule.txt"]
adjusted-file: read/lines chosen-file
insert next next next next adjusted-file submitted/4
write/lines chosen-file adjusted-file

count: 0
parse read join http://site.com/folders/ submitted/2 [
    thru submitted/2 copy p to "past students"
]
print {<wml>}

forskip p 130 [
    count: count + 1
    print rejoin [
        {<card id="} count {" title="} submitted/2 "-" count {"><p>}
    ]
    print rejoin [
        {<anchor>Next<go href="#} (count + 1) {"/></anchor>}
    ]
    print rejoin [{<anchor>Back<prev/></anchor>}]
    print copy/part p 130
    print {</p></card>}
]
print {</wml>}
quit

This script allows users to read email messages from any POP server, on their cell phone:

#!./rebol276 -cs
REBOL []
submitted: decode-cgi system/options/cgi/query-string
prin {Content-type: text/vnd.wap.wml^/^/}
prin {<?xml version="1.0" encoding="iso-8859-1"?>^/}
prin {<!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.1//EN"
"http://www.wapforum.org/DTD/wml_1.1.xml">^/}

accounts: [
    ["pop.server" "smtp.server" "username" "password" you@site.com]
    ["pop.server2" "smtp.server2" "username" "password" you@site2.com]
    ["pop.server3" "smtp.server3" "username" "password" you@site3.com]
]

if ((submitted/2 = none) or (submitted/2 = none)) [   
    print {<wml><card id="1" title="Select Account"><p>}
    print {Account: <select name="account">}
    forall accounts [
        print rejoin [
            {<option value="} index? accounts {">}
            last first accounts {</option>}
        ]
    ]
    print {</select>
    <select name="readorsend">
        <option value="readselect">Read</option>
        <option value="sendinput">Send</option>
    </select>
    <anchor>
       <go method="get" href="wapmail.cgi">
           <postfield name="account" value="$(account)"/>
           <postfield name="readorsend" value="$(readorsend)"/>
       </go>
       Submit
    </anchor>}
    print {</p></card></wml>}
    quit
]

if submitted/4 = "readselect" [
    t: pick accounts (to-integer submitted/2)
    system/schemes/pop/host:  t/1
    system/schemes/default/host: t/2
    system/schemes/default/user: t/3 
    system/schemes/default/pass: t/4 
    system/user/email: t/5
    prin {<wml><card id="1" title="Choose Message"><p>}
    prin rejoin [{<setvar name="account" value="} submitted/2 {"/>}]
    prin {<select name="chosenmessage">}
    mail: read to-url join "pop://" system/user/email
    foreach message mail  [
        pretty: import-email message
        if (find pretty/subject "***SPAM***") = none [
            replace/all pretty/subject {"} {}
            replace/all pretty/subject {&} {}
            prin rejoin [
                {<option value="} 
                pretty/subject
                {">}
                pretty/subject
                {</option>}
            ]
        ]
    ]
    print {</select>
    <anchor>
       <go method="get" href="wapmail.cgi">
           <postfield name="subroutine" value="display"/>
           <postfield name="chosenmessage" value="$(chosenmessage)"/>
           <postfield name="account" value="$(account)"/>
       </go>
       Submit
    </anchor>
    </p></card></wml>}
    quit
]

if submitted/2 = "display" [
    t: pick accounts (to-integer submitted/6)
    system/schemes/pop/host:  t/1
    system/schemes/default/host: t/2
    system/schemes/default/user: t/3 
    system/schemes/default/pass: t/4 
    system/user/email: t/5
    prin {<wml><card id="1" title="Display Message"><p>}
    mail: read to-url join "pop://" system/user/email
    foreach message mail  [
        pretty: import-email message
        if pretty/subject = submitted/4 [
            replace/all pretty/content {"} {}
            replace/all pretty/content {&} {}
            replace/all pretty/content {3d} {}
            ; prin pretty/content
            ; The line above often causes errors - we need to strip
            ; out HTML tags:
            strip: copy ""
            foreach item (load/markup pretty/content) [
                if ((type? item) = string!) [strip: join strip item]
            ]
            prin strip
        ]
    ]
    print {</p></card></wml>}
    quit
]

Creating WAP versions of your REBOL CGI scripts is a fantastic way to provide even more universal access to your important data.

16. Organizing Efficient Data Structures and Algorithms

The purpose of this tutorial is enable the use of a computing tool that improves productivity in business operations. Creating programs that execute quickly is an important goal toward that end, especially when dealing with large sets of data. In order to achieve speedy performance, it's critical to understand some fundamental concepts about efficient algorithmic design patterns and sensible techniques used to organize and store information effectively.

16.1 A Simple Loop Example

The example below provides a basic demonstration about how inefficient design can reduce performance. This code prints 30 lines of text to the REBOL interpreter console, each made up of 75 dash characters:

REBOL [title: "Badly Designed Line Printer"]
for i 1 30 1  [
    for i 1 75  1 [prin "-"]
    print ""
]
halt

Even on a very fast computer, you can watch the screen flicker, and see the characters appear as dashes are printed in a loop, 75 times per each line, across 30 lines. That inner character printing operation is repeated a total of 2250 times (30 lines * 75 characters). As it turns out, the REBOL "loop" function is slightly faster than the "for" function, when creating simple counted loop structures. So, you can see a slight performance improvement using the following code:

REBOL [title: "Slightly Improved Line Printer"]
loop 30 [
    loop 75 [prin "-"]
    print ""
]
halt

But the example above does not address the main bottle neck which slows down the display. The function that really takes time to execute is the "prin" function. The computer is MUCH slower at printing items to the screen, than it is at performing unseen computations in RAM memory. Watch how long it takes to simply perform the same set of loops and to increment a count (i.e., perform a sum computation), compared to printing during each loop. This example executes instantly, even on very slow computers:

REBOL [title: "Loops Without Printing"]
count: 0
loop 30 [
    loop 75 [count: count + 1]
]
print count
halt

A much more efficient design, therefore, would be to create a line of characters once, save it to a variable label, and then print that single saved line 30 times:

REBOL [title: "Well Designed Line Printer"]
line: copy {} 
loop 75 [append line "-"]
loop 30 [print line]
halt

The example above reduces the number of print functions from 2250 to 30, and the display is dramatically improved. The following code times the execution speed of each of the techniques above, so you can see just how much speed is saved by using memory and processing power more efficiently:

REBOL [title: "Printing Algorithm Timer"]

timer1: now/time/precise
for i 1 30 1  [
    for i 1 75  1 [prin "-"]
    print ""
]
elapsed1: now/time/precise - timer1
print newpage

timer2: now/time/precise
loop 30 [
    loop 75 [prin "-"]
    print ""
]
elapsed2: now/time/precise - timer2
print newpage

timer3: now/time/precise
count: 0
loop 30 [
    loop 75 [count: count + 1]
]
print count
elapsed3: now/time/precise - timer3
print newpage

timer4: now/time/precise
line: copy {} 
loop 75 [append line "-"]
loop 30 [print line]
elapsed4: now/time/precise - timer4
print newpage

print rejoin ["Printing 2250 characters, 'for':    " elapsed1]
print rejoin ["Printing 2250 characters, 'loop':   " elapsed2]
print rejoin ["Counting to 2250, printing result:  " elapsed3]
print rejoin ["Printing 30 preconstructed lines:   " elapsed4]

halt

This is, of course, a trivial demonstrative example, but identifying such "bottle necks", and designing code patterns which reduce loop counts and cut down on computational rigor, is a critical part of the thought process required to create fast and responsive applications. Knowing the benchmark speed of functions in a language, and understanding how to use effecient add-on tools such as database systems, can be helpful, but more often, smart architecture and sensible awareness of how data structures are organized, will have a much more dramatic effect on how well a program performs. When working with data sets that are expected to grow to a large scale, it's important to pay attention to how information will be stored and looped through, before any production code is written and implemented.

16.2 A Real Life Example: Checkout Register and Cashier Report System

The example below is the trivial POS example demonstrated earlier in the tutorial. It saves the data for all receipts in a single text file:

REBOL [title: "Minimal Cash Register - Inefficient"]
view gui: layout [
    style fld field 80
    across
    text "Cashier:"   cashier: fld 
    text "Item:"      item: fld 
    text "Price:"     price: fld [
        if error? try [to-money price/text] [alert "Price error" return]
        append a/text reduce [mold item/text "    " price/text newline]
        item/text: copy "" price/text: copy ""
        sum: 0
        foreach [item price] load a/text [sum: sum + to-money price]
        subtotal/text: form sum
        tax/text: form sum * .06
        total/text: form sum * 1.06 
        focus item
        show gui
    ]
    return
    a: area 600x300
    return
    text "Subtotal:"   subtotal: fld 
    text "Tax:"        tax: fld 
    text "Total:"      total: fld
    btn "Save" [
        items: replace/all (mold load a/text) newline " "
        write/append %sales.txt rejoin [
            items newline cashier/text newline now/date newline
        ]
        clear-fields gui
        a/text: copy ""             
        show gui             
    ]
]

This code reports the total of all items sold on any chosen day, by any chosen cashier:

REBOL [title: "Cashier Report - Ineffecient"]
report-date: request-date
report-cashier: request-text/title/default "Cashier:" "Nick"
sales: read/lines %sales.txt
sum: $0
foreach [items cashier date] sales [
    if ((report-cashier = cashier) and (report-date = to-date date)) [
        foreach [item price] load items [
            sum: sum + to-money price
        ]
    ]
]
alert rejoin ["Total for " report-cashier " on " report-date ": " sum]

This whole program appears to work just fine on first inspection, but what happens after a million sales transactions have been entered into the system? In that case, the report program must read in and loop through 3 million lines of data, perform the date and cashier comparison evaluations on every single sales entry, and then perform the summing loop on only the matching sales entries. That's a LOT of unnecessary processing, and reading data from the hard drive is particularly slow.

We could simply plan to occassionally copy, paste, and erase old transactions from the sales.txt file into a separate archive file. That would solve the problem (and may be a occasionally useful maintanence objective), but it doesn't really improve performance. By changing the method of storage just a bit, we can dramatically improve performance. The example below creates a new folder, and writes every sales transaction to a separate file. The FILE NAMES of saved sales contain the date, time, and cashier name of each transaction (only the code for the "Save" button has been changed slightly in this example):

REBOL [title: "Minimal Cash Register - Efficient"]
view gui: layout [
    style fld field 80
    across
    text "Cashier:"   cashier: fld 
    text "Item:"      item: fld 
    text "Price:"     price: fld [
        if error? try [to-money price/text] [alert "Price error" return]
        append a/text reduce [mold item/text "    " price/text newline]
        item/text: copy "" price/text: copy ""
        sum: 0
        foreach [item price] load a/text [sum: sum + to-money price]
        subtotal/text: form sum
        tax/text: form sum * .06
        total/text: form sum * 1.06 
        focus item
        show gui
    ]
    return
    a: area 600x300
    return
    text "Subtotal:"   subtotal: fld 
    text "Tax:"        tax: fld 
    text "Total:"      total: fld
    btn "Save" [
        file: copy to-file rejoin [
            now/date
            "_" replace/all form now/time ":" "-"
            "_" cashier/text
        ]
        save rejoin [%./sales/ file ] (load a/text)
        clear-fields gui
        a/text: copy ""
        show gui             
    ]
]

This improved report reads the list of file names in the %./sales/ folder. Each file name is parsed into date, time, and name components, and then, only if the date and cashier items match the report requirements, the loop that computes the sum is run. This eliminates a dramatic volume of data reading (only the file list is read - not the entire contents of every file), and avoids a tremendous number of unnecessary looped computational steps:

REBOL [title: "Cashier Report - Efficient"]
report-date: request-date
report-cashier: request-text/title/default "Cashier:" "Nick"
sum: $0
files: copy []
foreach file read %./sales/ [
    parsed: parse file "_"
    if ((report-date = to-date parsed/1) and (report-cashier = parsed/3))[
        append files file
    ]
]
cd %./sales/
foreach file files [ 
    foreach [item price] load file [
        sum: sum + to-money price
    ]
]
cd %../
alert rejoin ["Total for " report-cashier " on " report-date ": " sum]

When working with systems that are expected to handle large volumes of data, it's essential to run benchmark tests comparing potential design options. It's a simple task to write scripts which generate millions of entries of random data to test any system you create, at volume levels exceeding potential real life scenarios. Creating a script to generate random data to test the program above, for example, is as simple as looping the "Save" button code that creates the receipt files:

REBOL [title: "Automated Test Sales Data Generator"]
random/seed now/time/precise
loop 10000 [
    file: to-file rejoin [
        ((random 31-dec-0001) + 734868)   ; 734868 days between 2013/0001
        "_" replace/all form random 23:59:59 ":" "-"
        "_" random {abcd}
    ]        items: reduce [random "asd fgh jkl" random $100]
    save rejoin [%./sales/ file] items
]

Try running the following report after creating the above test data, and you'll see that results are calculated instantly:

REBOL [title: "Cashier Report - Efficient"]
report-date: request-date
report-cashier: request-text/title/default "Cashier:" "abcd"
sum: $0
files: copy []
foreach file read %./sales/ [
    parsed: parse file "_"
    if  report-cashier = parsed/3 [
        append files file
    ]
]
cd %./sales/
foreach file files [ 
    foreach [item price] load file [
        sum: sum + to-money price
    ]
]
cd %../
alert rejoin ["Total for " report-cashier ": " sum]

The method of saving structured data in separate text files, demonstrated by the simplified POS examples above, has been tested by the author in a variety of high volume commercial software implementations. The computational speed demonstrated by reports using this technique outperformed the capabilities of even powerful database systems. Other benefits, such as portability between systems (any operating system with a file structure can be used), no required DBMS installation, easy backup and transfer of data to other systems and mediums, etc., make this an extremely powerful way of approaching serious data management needs. Backing up all new data to a thumb drive is as simple as performing a folder sync. In one case, a web site reporting system was created to match a desktop POS reporting system that has tracked tens of millions of item sales. A simple REBOL script was used to upload new sales transaction files to the web server daily, and the exact same code was used to print the report as CGI script output. Users were then able to check sales online using browsers on any desktop PC, iPhone, Android, etc. Absolutely no database or machine dependent software architecture was required using this simple conceptual pattern of saving data to text files. The key to the success of this example of data organization, storage, and algorithmic report computation, is to simply engineer the system to store potentially searched data fields in the file names.

Learning to avoid wasted effort, and to pinpoint computational bottle necks, especially in loops that manage large data sets, is critical to designing fast applications. Even if you use powerful database systems to store data, it's still important to consider how you read, search, and otherwise manipulate the saved data. As a general rule, avoid reading, writing, transferring, or performing computations on anything other than the absolute smallest possible sets of values, and you'll find that performance can always be improved.

You'll see these sort of efficient design decisions applied to many applications in this tutorial. Pay particular attention to the way data is stored and reported in text files in the "RebGUI Point of Sale", "Simple POS", and "Simple POS Sales Report Printer" examples. More pointed techniques, such as the way in which messages were automatically moved to an "Archive" database in the "RebolForum" CGI application, help to dramatically improve the user experience by directly reducing the amount of data needed to present an initial display. That application has been tested in production situations, and responds instantly, even when the system contains many hundreds of thousands of messages.

It's important to consider the potential volume of data any system will be required to manage, before fully implementing the user interface and data structure in production environments. Consider and test all data fields that may be required as a system grows, and be sure your data structure and computational algorithms can handle more volume than will ever be needed. This will save you enormous headache down the road, when your software is firmly entrenched in business operations.

17. Additional Topics

17.1 Objects

Objects are code structures that allow you to encapsulate and replicate code. They can be thought of as code containers which are easily copied and modified to create multiple versions of similar code and/or duplicate data structures. They're also used to provide context and namespace management features (i.e., to avoid assigning the same variable words and/or function names to different pieces of code in large projects).

Object "prototypes" define a new object container. To create an original object prototype in REBOL, use the following syntax:

label: make object! [object definition]

The object definition can contain functions, values, and/or data of any type. Below is a blank user account object containing 6 variables which are all set to equal "none"):

account: make object! [
    first-name: last-name: address: phone: email-address: none
]

The account definition above simply wraps the 6 variables into a container, or context, called "account".

You can refer to data and functions within an object using refinement ("/path") notation:

object/word

In the account object, "account/phone" refers to the phone number data contained in the account. You can make changes to elements in an object as follows:

object/word: data

For example:

account/phone: "555-1234"
account/address: "4321 Street Place Cityville, USA 54321"

Once an object is created, you can view all its contents using the "help" function:

help object
? object  

; "?" is a synonym for "help"

If you've typed in all the account examples so far into the REBOL interpreter, then:

? account

displays the following info:

ACCOUNT is an object of value:
   first-name      none!     none
   last-name       none!     none
   address         string!   "4321 Street Place Cityville, USA 54321"
   phone           string!   "555-1234"
   email-address   none!     none

You can obtain a list of all the items in an object using the format "first (object label)":

first account

The above line returns [self first-name last-name address phone email-address]. The first item in the list is always "self", and for most operations, you'll want to remove that item. To do that, use the format "next first (object label)":

next first account

To iterate through every item in an object, you can use a foreach loop on the above values:

foreach item (next first account) [print item]

To get the values referred to by individual word labels in objects, use "get in":

get in account 'first-name
get in account 'address

; notice the tick mark

The following example demonstrates how to access and manipulate every value in an object:

count: 0
foreach item (next first account) [
    count: count + 1
    print rejoin ["Item " count ":   " item]
    print rejoin ["Value:    " (get in account item) newline]
]

Once you've created an object prototype, you can make a new object based on the original definition:

label: make existing-object [
    values to be changed from the original definition
]

This behaviour of copying values based on previous object definitions (called "inheritance") is one of the main reasons that objects are useful. The code below creates a new account object labeled "user1":

user1: make account [
    first-name: "John"
    last-name: "Smith"
    address: "1234 Street Place  Cityville, USA 12345"
    email-address: "john@hisdomain.com"
]

In this case, the phone number variable retains the default value of "none" established in the original account definition.

You can extend any existing object definition with new values:

label: make existing-object [new-values to be appended]

The definition below creates a new account object, redefines all the existing variables, and appends a new variable to hold the user's favorite color.

user2: make account [
    first-name: "Bob"
    last-name: "Jones"
    address: "4321 Street Place Cityville, USA 54321"
    phone:  "555-1234"
    email-address: "bob@mysite.net"
    favorite-color: "blue"
]

"user2/favorite-color" now refers to "blue".

The code below creates a duplicate of the user2 account, with only the name and email changed:

user2a: make user2 [
    first-name: "Paul"
    email-address: "paul@mysite.net"
]

"? user2a" provides the following info:

USER2A is an object of value:
   first-name      string!   "Paul"
   last-name       string!   "Jones"
   address         string!   "4321 Street Place Cityville, USA 54321"
   phone           string!   "555-1234"
   email-address   string!   "paul@mysite.net"
   favorite-color  string!   "blue"

You can include functions in your object definition:

complex-account: make object! [
    first-name: 
    last-name:
    address:
    phone:
    none
    email-address: does [
        return to-email rejoin [
            first-name "_" last-name "@website.com"
        ]
    ]
    display: does [
        print ""
        print rejoin ["Name:     " first-name " " last-name]
        print rejoin ["Address:  " address]
        print rejoin ["Phone:    " phone]
        print rejoin ["Email:    " email-address]
        print ""
    ]
]

Note that the variable "email-address" is initially assigned to the result of a function (which simply builds a default email address from the object's first and last name variables). You can override that definition by assigning a specified email address value. Once you've done that, the email-address function no longer exists in that particular object - it is overwritten by the specified email value.

Here are some implementations of the above object. Notice the email-address value in each object:

user1: make complex-account []

user2: make complex-account [
    first-name: "John"
    last-name: "Smith"
    phone:  "555-4321"
]

user3: make complex-account [
    first-name: "Bob"
    last-name: "Jones"
    address: "4321 Street Place Cityville, USA 54321"
    phone:  "555-1234"
    email-address: "bob@mysite.net"
]

To print out all the data contained in each object:

user1/display user2/display user3/display

The display function prints out data contained in each object, and in each object the same variables refer to different values (the first two emails are created by the email-address function, and the third is assigned).

Here's a small game in which multiple character objects are created from a duplicated object template. Each character can store, alter, and print its own separately calculated position value based on one object prototype definition:

REBOL []

hidden-prize: random 15x15
character: make object! [
    position: 0x0
    move: does [
        direction: ask "Move up, down, left, or right:  "
        switch/default direction [
            "up" [position: position + -1x0]
            "down" [position: position + 1x0]
            "left" [position: position + 0x-1]
            "right" [position: position + 0x1]
        ] [print newline print "THAT'S NOT A DIRECTION!"]
        if position = hidden-prize [
            print newline
            print "You found the hidden prize.  YOU WIN!"
            print newline
            halt
        ]
        print rejoin [
            newline
            "You moved character " movement " " direction
            ".  Character " movement " is now " 
            hidden-prize - position
            " spaces away from the hidden prize.  "
            newline
        ]
    ]
]
character1: make character[]
character2: make character[position: 3x3]
character3: make character[position: 6x6]
character4: make character[position: 9x9]
character5: make character[position: 12x12]
loop 20 [
    prin "^(1B)[J"
    movement: ask "Which character do you want to move (1-5)?  "
    if find ["1" "2" "3" "4" "5"] movement [
        do rejoin ["character" movement "/move"]
        print rejoin [
            newline
            "The position of each character is now:  "
            newline newline
            "CHARACTER ONE:   " character1/position newline
            "CHARACTER TWO:   " character2/position newline
            "CHARACTER THREE: " character3/position newline
            "CHARACTER FOUR:  " character4/position newline
            "CHARACTER FIVE:  " character5/position
        ]
        ask "^/Press the [Enter] key to continue."
    ]
]

You could, for example, extend this concept to create a vast world of complex characters in an online multi-player game. All such character definitions could be built from one base character definition containing default configuration values.

17.1.1 Namespace Management

In this example the same words are defined two times in the same program:

var: 1234.56
bank: does [
    print ""
    print rejoin ["Your bank account balance is:  $" var]
    print ""
]

var: "Wabash"
bank: does [
    print ""
    print rejoin [
        "Your favorite place is on the bank of the:  " var]
    print ""
]

bank

There's no way to access the bank account balance after the above code runs, because the "bank" and "var" words have been overwritten. In large coding projects, it's easy for multiple developers to unintentionally use the same variable names to refer to different pieces of code and/or data, which can lead to accidental deletion or alteration of values. That potential problem can be avoided by simply wrapping the above code into separate objects:

money: make object! [
    var: 1234.56
    bank: does [
        print ""
        print rejoin ["Your bank account balance is:  $" var]
        print ""
    ]
]

place: make object! [
    var: "Wabash"
    bank: does [
        print ""
        print rejoin [
            "Your favorite place is on the bank of the:  " var]
        print ""
    ]
]

Now you can access the "bank" and "var" words in their appropriate object contexts:

money/bank
place/bank

money/var
place/var

The objects below make further use of functions and variables contained in the above objects. Because the new objects "deposit" and "travel" are made from the "money" and "place" objects, they inherit all the existing code contained in the above objects:

deposit: make money [
    view layout [
        button "Deposit $10" [
            var: var + 10
            bank
        ]
    ]
]

travel: make place [
    view layout [
        new-favorite: field 300 trim {
            Type a new favorite river here, and press [Enter]} [
            var: value
            bank
        ]
    ]
]

Learning to use objects is important because much of REBOL is built using object structures. As you've seen earlier in the section about built-in help, the REBOL "system" object contains many important interpreter settings. In order to access all the values in the system object, it's essential to understand object notation:

get in system/components/graphics 'date

The same is true for GUI widget properties and many other features of REBOL.

For more information about objects, see:

http://rebol.com/docs/core23/rebolcore-10.html
http://en.wikibooks.org/wiki/REBOL_Programming/Language_Features/Objects
http://en.wikipedia.org/wiki/Prototype-based_programming

17.2 Ports - Fine Grained Access to Files, Email, Network and More

REBOL "ports" provide a single way to handle many types of data input and output. They enable access to a variety of data sources, and allow you to control them all in a consistent way, using standard REBOL series functions. You can open ports to POP email boxes, FTP directories, local text files, TCP network connections, keyboard input buffers, and more, and also use them to output data such as sounds and console interactions. Once a port is opened to a data source, the data contained in the port can be treated as a sequential list of items which can be traversed, arranged, searched, sorted, and otherwise organized/manipulated, all using series functions such as those covered earlier in this text (foreach, find, select, reverse, length?, head, next, back, last, tail, at, skip, extract, index?, insert, append, remove, change, poke, copy/part, clear, replace, join, intersect, difference, exclude, union, unique, empty?, write, save, etc.).

In some cases, there are other native ways to access data contained in a given port, typically with "read" and "write" functions. In such cases, port access simply provides finer control of the data (dealing with email and file data are examples of such cases). In other cases, ports provide the primary interface for accessing data in the given data source (TCP sockets and other network protocols are examples).

Ports are created using the "open" function, and are typically assigned a word label when created:

my-files: open ftp://user:pass@site.com/public_html/

After opening the above port, the files in the FTP directory can be traversed sequentially or by index, using series functions:

print first my-files
print length? my-files
print pick my-files ((length? my-files) - 7)  ; 7th file from the end

; etc ...

To change the marked index position in a port, re-assign the port label to the new index position:

my-files: head my-files
    print index? my-files
    print first my-files
my-files: next my-files
    print index? my-files
    print first my-files
my-files: at my-files 10
    print index? my-files
    print first my-files

To close the connection to data contained in a port, use the "close" function:

close my-files

It is of course possible to read and write directly to/from the folder in the above examples without manually opening a port:

print read ftp://user:pass@site.com/public_html/
write ftp://user:pass@site.com/public_html/temp.txt (read %temp.txt)

The difference between opening a port to the above files, and simply reading/writing them is that the port connection offers more specific access to and control of individual files. The "get-modes" and "set-modes" functions can be used to set various properties of files:

my-file: open %temp.txt
set-modes port [
    world-read: true
    world-write: true
    world-execute: true
]
close my-file

More benefits of port control are easy to understand when dealing with email accounts. All the email in a given account can be accessed by simply reading it:

print read pop://user:pass@site.com

If, for example, there are 10000 messages in the above email account, the above action could take a very long time to complete. Even to simply read one email from the above account, the entire account needs to be read:

print second read pop://user:pass@site.com

A much better solution is to open a port to the above data source:

my-email: open pop://user:pass@site.com

Once the above port is open, each of the individual emails in the given POP account can be accessed separately, without having to download any other emails in the account:

print second my-email  ; no download of 10000 emails required

And you can jump around between messages in the account:

my-email: head my-email
    print first my-email   ; prints the 1st email in the box
my-email: next my-email
    print first my-email   ; prints the 2nd email in the box
my-email: at my-email 4
    print first my-email   ; prints the 5th email in the box
my-email: head my-email
    print first my-email   ; prints email #1 again

; etc...

You can also remove email messages from the account:

my-email: head my-email
    remove my-email  ; removes the 1st email

Internally, REBOL actually deals with most types of data sources as ports. The following line:

write/append %temp.txt "1234"

Is the same as:

temp: open %temp.txt
append temp "1234"
close temp

REBOL ports are objects. You can see all the properties of an open port, using the "probe" function:

temp: open %temp.txt
probe temp
close temp

From the very important example above, you can see that various useful properties of the port data can be accessed using a consistent syntax:

temp: open %temp.txt

print temp/date
print temp/path
print temp/size

close temp

The state/inBuffer and state/outBuffer are particularly important values in any port. Those items are where changes to data contained in the port are stored, until the port is closed or updated. Take a close look at this example:

; First, create a file:

write %temp.txt ""

; That file is now empty:

print read %temp.txt

; Open the above file as a port:

temp: open %temp.txt

; Append some text to it:

append temp "1234"

; Display the text to be saved to the file:

print temp/state/inBuffer

; The appended changes have NOT yet been saved to the file because the
; port has not yet been closed or updated:

print read %temp.txt

; Either "update" or "close" can be used to save the changes to the file:

update temp

; The "update" function has forced the appended data to be written to
; the file, but has NOT yet closed the port:

print read %temp.txt

; We can still navigate the port contents and add more data to it:

temp: head temp
insert temp "abcd"

; Display the text to be saved to the file:

print temp/state/inBuffer

; Those changes have not yet been saved to the file:

print read %temp.txt

; Closing the port will save changes to the file:

close temp

; Here are the saved changes:

print read %temp.txt

; And additional changes can no longer be made:

append temp "1q2w3e4r"  ; (error)

Ports can be opened with a variety of refinements to help deal with data appropriately. "Help open" displays the following list:

/binary  - Preserves contents exactly.
/string  - Translates all line terminators.
/direct  - Opens the port without buffering.
/seek    - Opens port in seek mode without buffering.
/new     - Creates a file. (Need not already exist.)
/read    - Read only. Disables write operations.
/write   - Write only.  Disables read operations.
/no-wait - Returns immediately without waiting if no data.
/lines   - Handles data as lines.
/with    - Specifies alternate line termination. (Type: char string)
/allow   - Specifies the protection attributes when created. (Type: block)
/mode    - Block of above refinements. (Type: block)
/custom  - Allows special refinements. (Type: block)
/skip    - Skips a number of bytes. (Type: number)

Several of those options will be demonstrated in the following example applications.

17.3 Console and CGI Email Apps Using Ports

The following email program opens a port to a selected email account and allows the user to navigate through messages, read, send, delete, and reply to emails. It runs entirely at the command line - no VID GUI components or View graphics are required. You can store configuration information for as many email accounts as you'd like in the "accounts" block, and easily switch between them at any point in the program:

REBOL [Title: "Console Email"]

accounts: [
    ["pop.server" "smtp.server" "username" "password" you@site.com]
    ["pop.server2" "smtp.server2" "username" "password" you@site2.com]
    ["pop.server3" "smtp.server3" "username" "password" you@site3.com]
]

empty-lines: "^/"
loop 400 [append empty-lines "^/"]  ; # of lines it takes to clear screen
cls: does [prin {^(1B)[J}]
a-line:{-----------------------------------------------------------------}

select-account: does [
    cls
    print a-line
    forall accounts [
        print rejoin ["^/" index? accounts ":  " last first accounts]
    ]
    print join "^/" a-line
    selected: ask "^/Select an account #:  "
    if selected = "" [selected: 1]
    t: pick accounts (to-integer selected)
    system/schemes/pop/host:  t/1
    system/schemes/default/host: t/2
    system/schemes/default/user: t/3 
    system/schemes/default/pass: t/4 
    system/user/email: t/5
]
send-email: func [/reply] [
    cls
    print rejoin [a-line "^/^/Send Email:^/^/" a-line] 
    either reply [
        print join "^/^/Reply-to:  " addr: form pretty/from
    ] [
        addr: ask "^/^/Recipient Email Address:  "
    ]
    either reply [
        print join "^/Subject:  " subject: join "re: " form pretty/subject
    ] [
        subject: ask "^/Email Subject:  "
    ]
    print {^/Body (when finished, type "end" on a seperate line):^/}
    print join a-line "^/"
    body: copy ""
    get-body: does [
        body-line: ask ""
        if body-line = "end" [return]
        body: rejoin [body "^/" body-line]
        get-body
    ]
    get-body
    if reply [
        rc: ask "^/Quote original email in your reply (Y/n)?  "
        if ((rc = "yes") or (rc = "y") or (rc = "")) [
            body: rejoin [
                body 
                "^/^/^/--- Quoting " form pretty/from ":^/"
                form pretty/content
            ]
        ]
    ]
    print rejoin ["^/" a-line "^/^/Sending..."]
    send/subject to-email addr body subject 
    cls 
    print "Sent^/" 
    wait 1
]
read-email: does [
    pretty: none
    cls
    print "One moment..."
    ; THE FOLLOWING LINE OPENS A PORT TO THE SELECTED EMAIL ACCOUNT:
    mail: open to-url join "pop://" system/user/email
    cls
    while [not tail? mail] [
        print "Reading...^/"
        pretty: import-email (copy first mail)
        either find pretty/subject "***SPAM***" [
            print join "Spam found in message #" length? mail
            mail: next mail
        ][
            print empty-lines
            cls
            prin rejoin [
                a-line
                {^/The following message is #} length? mail { from:  } 
                system/user/email {^/} a-line {^/^/}
                {FROM:     } pretty/from {^/}
                {DATE:     } pretty/date {^/}
                {SUBJECT:  } pretty/subject {^/^/} a-line
            ]
            confirm: ask "^/^/Read Entire Message (Y/n):  "
            if ((confirm = "y") or (confirm = "yes") or (confirm = "")) [
                print join {^/^/} pretty/content
            ]
            print rejoin [
                {^/} a-line {^/}
                {^/[ENTER]:  Go Forward  (next email)^/}
                {^/    "b":  Go Backward (previous email)^/}
                {^/    "r":  Reply to current email^/}
                {^/    "d":  Delete current email^/}
                {^/    "q":  Quit this mail box^/}
                {^/  Any #:  Skip forward or backward this # of messages}
                {^/^/} a-line {^/}
            ]
            switch/default mail-command: ask "Enter Command:  " [
                ""  [mail: next mail]
                "b" [mail: back mail]
                "r" [send-email/reply]
                "d" [
                    remove mail
                    cls 
                    print "Email deleted!^/" 
                    wait 1
                ]
                "q" [
                    close mail
                    cls
                    print"Mail box closed^/"
                    wait 1 
                    break
                ]
            ] [mail: skip mail to-integer mail-command]
            if (tail? mail) [mail: back mail]
        ]
    ]
]

; begin the program:

select-account

forever [
    cls
    print a-line
    print rejoin [
        {^/"r":  Read Email^/}
        {^/"s":  Send Email^/}
        {^/"c":  Choose a different mail account^/}
        {^/"q":  Quit^/}
    ]
    print a-line
    response: ask "^/Select a menu choice:  "
    switch/default response [
        "r" [read-email]
        "s" [send-email]
        "c" [select-account]
        "q" [
            cls
            print "DONE!"
            wait .5 
            quit
        ]
    ] [read-email]
]

Here is a CGI version of an email program that runs on a web server and operates in the absolute simplest browsers (this app was created to run in the bare bones experimental browser that came with the first Amazon Kindle book reader):

#!../rebol276 -cs
REBOL [Title: "Kindle Email"]
print {content-type: text/html^/^/}
print {<HTML><HEAD><TITLE>Kindle Email</TITLE></HEAD><BODY>}
read-cgi: func [/local data buffer][
    switch system/options/cgi/request-method [
        "POST" [
            data: make string! 1020
            buffer: make string! 16380
            while [positive? read-io system/ports/input buffer 16380][
                append data buffer
                clear buffer
            ]
        ]
        "GET" [data: system/options/cgi/query-string]
    ]
    data
]
submitted: decode-cgi submitted-bin: read-cgi
if ((submitted/2 = none) or (submitted/4 = none)) [
    print {
        <STRONG>W A R N I N G  -  Private Server:</STRONG><BR><BR>
        <FORM METHOD="post" ACTION="./kindle_email.cgi">
            Username: <input type=text size="50" name="name"><BR><BR>
            Password: <input type=text size="50" name="pass"><BR><BR>
            <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="submit">
        </FORM>
        </BODY></HTML>
    } 
    quit
]
accounts: [
    ["pop.server1" "smtp.server1" "username1" "password1" you@site1.com]
    ["pop.server2" "smtp.server2" "username2" "password2" you@site2.com]
    ["pop.server3" "smtp.server3" "username3" "password3" you@site3.com]
]
myusername: "username"  mypassword: "password"
username: submitted/2   password: submitted/4 
either ((username = myusername) and (password = mypassword)) [][
    print "Incorrect Username/Password." 
    print {</BODY></HTML>} quit
]
if submitted/6 = "read" [
    account: pick accounts (to-integer submitted/8)
    mail-content: read [
        scheme: 'POP
        host: account/1
        port-id: 110
        user: account/3
        pass: account/4
    ]
    mail-count: length? mail-content
    for i 1 mail-count 1 [
        single-message: import-email (pick mail-content i)
        print rejoin [
            i {) &nbsp; <a href="./kindle_email.cgi?} 
            {u=} myusername {&p=} mypassword 
            {&subroutine=displaymessage&themessage=} 
            ; copy/part for URI length, at 3 is a serialization trick:
            at (mold compress (copy/part single-message/content 5000)) 3
            {">} single-message/subject
            {</a> &nbsp; <a href="./kindle_email.cgi?} 
            {u=} myusername {&p=} mypassword 
            {&subroutine=delete&theaccount=} submitted/8
            {&thesubject=} single-message/subject 
            {&thedate=} single-message/date
            {&thefrom=} single-message/from {">delete</a>
            <br> &nbsp; &nbsp; &nbsp; &nbsp; } single-message/from {<br>}
        ]
    ]
    quit
]
if submitted/6 = "displaymessage" [
    compressed-message: copy join "#{" submitted/8
    print "<pre>"  print decompress load compressed-message  print "<pre>"
    quit
]
if ((submitted/6 = "send") or (submitted/6 = "delete")) [
    my-account: pick accounts (to-integer submitted/8)
    system/schemes/pop/host:  my-account/1
    system/schemes/default/host: my-account/2
    system/schemes/default/user: my-account/3 
    system/schemes/default/pass: my-account/4 
    system/user/email: my-account/5
] 
if submitted/6 = "send" [
    print "Sending..."
    header: make system/standard/email [
        To: to-email submitted/10
        From: to-email my-account/5
        Subject: submitted/12
    ]
    send/header (to-email submitted/10) (trim submitted/14) header
    print "<strong>Sent</strong>"
]
if submitted/6 = "delete" [
    mail: open to-url join "pop://" system/user/email
    while [not tail? mail] [
        pretty: import-email (copy first mail)
        either all [
            pretty/subject = submitted/10
            form pretty/date = submitted/12
            form pretty/from = submitted/14
        ][
            remove mail  print "<strong>Deleted</strong>"  wait 1
        ][
            mail: next mail
        ]
    ]
]
print {<hr><h2>Read:</h2>}
for i 1 (length? accounts) 1 [
    print rejoin [
        i {) &nbsp; <a href="./kindle_email.cgi?}
        {u=} myusername {&p=} mypassword {&subroutine=read&accountname=}
        i {">} (first pick accounts i) {</a><br>}
    ]
]
print rejoin [
    {<BR><HR>
    <h2>Send:</h2>
    <FORM METHOD="post" ACTION="./kindle_email.cgi">
        <INPUT TYPE=hidden NAME="username" VALUE="} myusername {">
        <INPUT TYPE=hidden NAME="password" VALUE="} mypassword {">
        <INPUT TYPE=hidden NAME="subroutine" VALUE="send">
        From Account #: <select NAME="account">}
]
for i 1 (length? accounts) 1 [prin rejoin [{<option>} i]]
print {
        </option> </select><br><br>
        To: <BR><input type=text size="35" name="to"><BR><BR>
        Subject: <BR><input type=text size="35" name="subject"><BR><BR>
        <TEXTAREA COLS="50" ROWS="18" NAME="contents"></TEXTAREA><BR><BR>
        <INPUT TYPE="SUBMIT" NAME="Submit" VALUE="submit">
    </FORM>
    </BODY></HTML>
}
quit

17.4 Network Ports - Transferring Data and Files with HTTP

One important use of ports is for transferring data via network connections (TCP and UDP "sockets"). When writing a network application, you must choose a specific port number through which data is to be transferred. Potential ports range from 0 to 65535, but many of those numbers are reserved for specific types of applications (email programs use port 110, web servers use port 80 by default, etc.). To avoid conflicting with other established network applications, it's best to choose a port number between 49152 and 65535 for small scripts. A list of reserved port numbers is available here.

Network applications are typically made up of two or more separate programs, each running on different computers. Any computer connected to a network or to the Internet is assigned a specific "IP address", notated in the format xxx.xxx.xxx.xxx. The numbers are different for every machine on a network, but most home and small business machines are normally in the IP range "192.168.xxx.xxx". You can obtain the IP address of your local computer with the following REBOL code:

read join dns:// (read dns://)

"Server" programs open a chosen network port and wait for one or more "client" programs to open the same port and then insert data into it. The port opened by the server program is referred to in a client program by combining the IP address of the computer on which the server runs, along with the chosen port number, each separated by a colon symbol (i.e., 192.168.1.2:55555).

The following simple set of scripts demonstrates how to use REBOL ports to transfer one line of text from a client to a server program. This example is intended to run on a single computer, for demonstration, so the word "localhost" is used to represent the IP address of the server (that's a standard convention used to refer to any computer's own local IP address). If you want to run this on two separate computers connected via a local area network, you'll need to obtain the IP address of the server machine (use the code above), and replace the word "localhost" with that number:

Here's the SERVER program. Be sure to run it before starting the client, or you will receive an error:

; Open network port 55555, in line mode (this mode expects full lines
; of text delineated by newline characters):

server: open/lines tcp://:55555

; Wait for a connection to the above port:

wait server

; Assign a label to the first connection made to the above port:

connection: first server

; Get the data which has been inserted into the above port object:

data: first connection

; Display the inserted data:

alert rejoin ["Text received: " data]

; Close the server

close server

Here's the CLIENT. Run it in a separate instance of the REBOL interpreter, after the above program has been started:

; Open the port created by the server above (replace "localhost" with
; an IP address if running these scripts on separate machines):

server-port: open/lines tcp://localhost:55555

; Insert some text into the port:

insert server-port "Hello Mr. Watson."

; Close the port:

close server-port

Typically, servers will continuously wait for data to appear in a port, and repeatedly do something with that data. The scripts below extend the above example with forever loops to continuously send, receive, and display messages transferred from client(s) to the server. This type of loop forms the basis for most peer-to-peer and client-server network applications. Type "end" in the client program below to quit both the client and server.

Here's the server program (run it first):

server: open/lines tcp://:55555             ; Open a TCP network port.
print "Server started...^/"
connection: first wait server               ; Label the first connection.
forever [
    data: first connection                  ; Get a line of data.
    print rejoin ["Text received: " data]   ; Display it.
    if find data "end" [                    
        close server                        ; End the program if the
        print "Server Closed"               ;   client user typed "end".
        halt
    ]
]

Here's the client program. Run it only after the server program has been started, and in a separate instance of the REBOL interpreter (or on a separate computer):

server-port: open/lines tcp://localhost:55555    ; Open the server port.
forever [
    user-text: ask "Enter some text to send:  "
    insert server-port user-text                 ; Transfer the data.
    if user-text = "end" [
        close server-port                        ; End the program if the
        print "Client Closed"                    ; user typed "end".
        halt
    ]
]

It's important to understand that REBOL servers like the one above can interact independently with more than one simultaneous client connection. The "connection" definition waits until a new client connects, and returns a port representing that first client connection. Once that occurs, "connection" refers to the port used to accept data transferred by the already connected client. If you want to add more simultaneous client connections during the forever loop, simply define another "first wait server". Try running the server below, then run two simultaneous instances of the above client:

server: open/lines tcp://:55555             ; Open a TCP network port.
print "Now start TWO clients..."
connection1: first wait server              ; Label the first connection.
connection2: first wait server              ; Label the second connection.
forever [
    data1: first connection1                ; Get a line of client1 data
    data2: first connection2                ; Get a line of client2 data
    print rejoin ["Client1: " data1]
    print rejoin ["Client2: " data2]
    if find data1 "end" [                    
        close server                        ; End the program if the
        print "Server Closed"               ;   client user typed "end".
        halt
    ]
]

Here's an example that demonstrates how to send data back and forth (both directions), between client and server. Again, run both programs in separate instances of the REBOL interpreter, and be sure to start the server first:

; Server:

print "Server started...^/"
port: first wait open/lines tcp://:55555
forever [
    user-text: ask "Enter some text to send:  "
    insert port user-text
    if user-text = "end" [close port  print "^/Server Closed^/"  halt]
    wait port
    print rejoin ["^/Client user typed:  " first port "^/"]
]

; Client:

port: open/lines tcp://localhost:55555
print "Client started...^/"
forever [
    user-text: ask "Enter some text to send:  "
    insert port user-text
    if user-text = "end" [close port  print "^/Client Closed^/"  halt]
    wait port
    print rejoin ["^/Server user typed:  " first port "^/"]
]

The following short script combines many of the techniques demonstrated so far. It can act as either server or client, and can send messages (one at a time), back and forth between the server and client:

do [
    either find ask "Server or client?  " "s" [
        port: first wait open/lines tcp://:55555 ; server
    ] [
        port: open/lines tcp://localhost:55555   ; client
    ]
    forever [
        insert port ask "Send:  "
        print join "Received: "first wait port
    ] 
]

The following script is a complete GUI network instant message application. Unlike the FTP Chat Room presented earlier, the text in this application is sent directly between two computers, across a network socket connection (users of the FTP chat room never connect directly to one another - they simply connect to a universally available third party FTP server):

view layout [
    btn "Set client/server" [
        ip: request-text/title/default trim {
            Server IP (leave EMPTY to run as SERVER):
            } (to-string read join dns:// read dns://)
        either ip = "" [
            port: first wait open/lines tcp://:55555 z: true ; server
        ] [
            port: open/lines rejoin [tcp:// ip ":55555"] z: true
        ]
    ]
    r: area rate 4 feel [
        engage: func [f a e] [
            if a = 'time and value? 'z [
                if error? try [x: first wait port] [quit]
                r/text: rejoin [form x newline r/text] show r
            ]
        ]
    ]
    f: field "Type message here..."
    btn "Send" [insert port f/text] 
]

Here's an even more compact version (probably the shortest instant messenger program you'll ever see!):

view layout [ across
    q: btn "Serve"[focus g p: first wait open/lines tcp://:8 z: 1]text"OR"
    k: btn "Connect"[focus g p: open/lines rejoin[tcp:// i/text ":8"]z: 1]
    i: field form read join dns:// read dns://  return
    r: area rate 4 feel [engage: func [f a e][if a = 'time and value? 'z [
        if error? try [x: first wait p] [quit]
        r/text: rejoin [x "^/" r/text] show r
    ]]]  return
    g: field "Type message here [ENTER]" [insert p value  focus face]
]

And here's an extended version of the above script that uploads your chosen user name, WAN/LAN IP, and port numbers to an FTP server, so that that info can be shared with others online (which enables them to find and connect with you). Connecting as server uploads the user info and starts the application in server mode. Once that is done, others can click the "Servers" button to retrieve and manually enter your connection info (IP address and port), to connect as client. By using different port numbers and user names, multiple users can connect to other multiple users, anywhere on the Internet:

server-list: ftp://username:password@yoursite.com/public_html/im.txt ;edit
view layout [ across
    q: btn "Serve" [
        parse read http://guitarz.org/ip.cgi[thru<title>copy p to</title>]
        parse p [thru "Your IP Address is: " copy pp to end]
        write/append server-list rejoin [
            b/text " " pp " " read join dns:// read dns://"  " j/text "^/"
        ] 
        focus g p: first wait open/lines join tcp:// j/text z: 1
    ] text "OR"
    k: btn "Connect" [
        focus g p: open/lines rejoin [tcp:// i/text j/text] z: 1
    ]
    b: field 85 "Username"
    i: field 98 form read join dns:// read dns:// 
    j: field 48 ":8080" return
    r: area rate 4 feel [engage: func [f a e][if a = 'time and value? 'z [
        if error? try [x: first wait p] [quit]
        r/text: rejoin [x "^/" r/text] show r
    ]]]  return
    g: field "Type message here [ENTER]" [insert p value  focus face]
    tabs 181 tab btn "Servers" [print read server-list]
]

If you want to run scripts like these between computers connected to the Internet by broadband routers, you'll likely need to learn how to "forward" ports from your router to the IP address of the machine running your server program. In most situations where a router connects a local home/business network to the Internet, only the router device has an IP address which is visible on the Internet. The computers themselves are all assigned IP addresses that are only accessible within the local area network. Port forwarding allows you to send data coming to the IP address of the router (the IP which is visible on the Internet), on a unique port, to a specific computer inside the local area network. A full discussion of port forwarding is beyond the scope of this tutorial, but it's easy to learn how to do - just type "port forwarding" into Google. You'll need to learn how to forward ports on your particular brand and model of router.

With any client-server configuration, only the server machine needs to have an exposed IP address or an open router/firewall port. The client machine can be located behind a router or firewall, without any forwarded incoming ports.

Another option that enables network applications to work through routers is "VPN" software. Applications such as hamachi, comodo, and OpenVPN allow you to connect two separate LAN networks across the Internet, and treat all the machines as if they are connected locally (connect to any computer in the VPN using a local IP address, such as 192.168.1.xxx). VPN software also typically adds a layer of security to the data sent back and forth between the connected machines. The down side of VPN software is that data transmission can be slower than direct connection using port forwarding (the data travels through a third party server).

17.4.1 Peer-to-Peer Instant Messenger

The following text message example contains line by documentation of various useful coding techniques. For instructions, see the help documentation included in the code.

REBOL [Title: "Peer-to-Peer Instant Messenger"]

; The following line sets a flag variable, used to mark whether or not
; the two machines have already connected.  It helps to more gracefully
; handle connection and shutdown actions throughout the script:

connected: false

; The code below traps the close button (just a variation of the routine
; used in the earlier listview example).  It assures that all open ports
; are closed, and sends a message to the remote machine that the
; connection has been terminated.  Notice that the lines in the disconnect
; message are sent in reverse order.  When they're received by the other
; machine, they're printed out one at a time, each line on top of the
; previous - so it appears correctly when viewed on the other side:

insert-event-func closedown: func [face event] [
    either event/type = 'close [
        if connected [
            insert port trim {
                *************************************************
                AND RECONNECT.
                YOU MUST RESTART THE APPLICATION
                TO CONTINUE WITH ANOTHER CHAT,
                THE REMOTE PARTY HAS DISCONNECTED.
                *************************************************
            }
            close port
            if mode/text = "Server Mode" [close listen]
        ]
        quit
    ] [event]
]

view/new center-face gui: layout [
    across
    at 5x2  ; this code positions the following items in the GUI

    ; The text below appears as a menu option in the upper
    ; left hand corner of the GUI.  When it's clicked, the
    ; text contained in the "display" area is saved to a 
    ; user selected file:

     text bold "Save Chat" [
        filename: to-file request-file/title/file/save trim {
            Save file as:} "Save" %/c/chat.txt
        write filename display/text 
    ]

    ; The text below is another menu option.  It displays
    ; the user's IP address when clicked.  It relies on a
    ; public web server to find the external address.
    ; The "parse" command is used to extract the IP address
    ; from the page.  Parse is covered in a separate
    ; dedicated section later in the tutorial.

    text bold "Lookup IP" [
        parse read http://guitarz.org/ip.cgi [
            thru <title> copy my-ip to </title>
        ]
        parse my-ip [
            thru "Your IP Address is: " copy stripped-ip to end
        ]
        alert to-string rejoin [
            "External: " trim/all stripped-ip "  "
            "Internal: " read join dns:// read dns://
        ]
    ]

    ; The text below is a third menu option.  It displays 
    ; the help text when clicked.

     text bold "Help" [
        alert {
        Enter the IP address and port number in the fields
        provided.  If you will listen for others to call you, 
        use the rotary button to select "Server Mode" (you
        must have an exposed IP address and/or an open port
        to accept an incoming chat).  Select "Client Mode" if
        you will connect to another's chat server (you can do
        that even if you're behind an unconfigured firewall, 
        router, etc.).  Click "Connect" to begin the chat. 
        To test the application on one machine, open two
        instances of the chat application, leave the IP set
        to "localhost" on both.  Set one instance to run as 
        server, and the other as client, then click connect.
        You can edit the chat text directly in the display
        area, and you can save the text to a local file.
        }
    ]
    return

    ; Below are the widgets used to enter connection info.
    ; Notice the labels assigned to each item.  Later, the
    ; text contained in these widgets is referred to as
    ; <label>/text.  Take a good look at the action block 
    ; for the rotary button too.  Whenever it's clicked, 
    ; it either hides or shows the other widgets.  When in
    ; server mode, no connection IP address is needed - the
    ; application just waits for a connection on the given
    ; port.  Hiding the IP address field spares the user some
    ; confusion.

    lab1: h3 "IP Address:"  IP: field "localhost" 102
    lab2: h3 "Port:" portspec: field "9083" 50
    mode: rotary 120 "Client Mode" "Server Mode" [
        either value = "Client Mode" [
            show lab1 show IP
        ][
            hide lab1 hide IP
        ]
    ]

    ; Below is the connect button, and the large action block
    ; that does most of the work.  When the button is clicked,
    ; it's first hidden, so that the user isn't tempted to
    ; open the port again (that would cause an error).  Then,
    ; a TCP/IP port is opened - the type (server/client) is
    ; determined using an "either" construct.  If an error
    ; occurs in either of the port opening operations, the
    ; error is trapped and the user is alerted with a message -
    ; that's more graceful and informative than letting the 
    ; program crash with an error.  Notice that the IP
    ; address and port info are gathered from the fields above.
    ; If the server mode is selected (i.e., if the "mode" button
    ; above isn't displaying the text "Client Mode"), then the
    ; the TCP ports are opened in listening mode - waiting
    ; for a client to connect.  If the client mode is selected,
    ; an attempt is made to open a direct connection to the IP
    ; address and port selected. 

    cnnct: button red "Connect" [
        hide cnnct
        either mode/text = "Client Mode" [
            if error? try [
                port: open/direct/lines/no-wait to-url rejoin [
                    "tcp://" IP/text ":" portspec/text]
            ][alert "Server is not responding." return]
        ][
            if error? try [
                listen: open/direct/lines/no-wait to-url rejoin [
                    "tcp://:" portspec/text]
                wait listen
                port: first listen
            ][alert "Server is already running." return]
        ]

        ; After the ports have been opened, the text entry field
        ; is highlighted, and the connection flag is set to true.
        ; Focusing on the text entry field provides a nice visual
        ; cue to the user that the connection has been made, but
        ; it's not required.

        focus entry
        connected: true

        ; The forever loop below continuously waits for data to
        ; appear in the open network connection.  Whenever data
        ; is inserted on the other side, it's copied and
        ; appended to the current text in the display area, and
        ; then the display area is updated to show the new text.

        forever [
            wait port
            foreach msg any [copy port []] [
                display/text: rejoin [
                    ">>>  "msg newline display/text]
            ]
            show display
        ]
    ]

    ; Below are the display area and text entry fields.  Notice
    ; the labels assigned to each.  The "return"s just put each
    ; widget on a new line in the GUI (because the layout mode
    ; is set to "across" above).

    return  display: area "" 537x500
    return  entry: field 428  ; the numbers are pixel sizes

    ; The send button below does some more important work.
    ; First, it checks to see if the connection has been made
    ; (using the flag set above).  If so, it inserts the text
    ; contained in the "entry" field above into the open TCP/IP
    ; port, to be picked up by the remote machine - if the 
    ; connection has been made, the program on the other end
    ; is waiting to read any data inserted into that port.
    ; After sending the data across the network connection,
    ; the text is appended to the local current text display
    ; area, and the display is updated:

    button "Send Text" [
        if connected [
            insert port entry/text focus entry
            display/text: rejoin [
                "<<<  " entry/text newline display/text]
            show display
        ]
    ]
]

show gui do-events  ; these are required because the "/new"
                    ; refinement is used above.

17.5 Transferring Binary Files Through TCP Network Sockets

These 2 scripts based on http://www.rebol.net/cookbook/recipes/0058.html, by Carl Sassenrath (edited and condensed here), demonstrate how to transfer binary files directly between any two networked computers (across a TCP socket connection), using ports. Sending binary files is different from sending text in that the length of the file must be transmitted before sending the file. That must be done so that the receiving code knows when the complete file has been transmitted. The sending script below appends the file length information, and the file name, to the data being sent. The receiving script searches for that information, then receives the specified amount of binary data and saves it to a file when complete:

REBOL [Title: "Server/Receiver"]

p: ":8000"  ; port #
print "receiving"

data: copy wait client: first port: wait open/binary/no-wait join tcp:// p
info: load to-string copy/part data start: find data #""
remove/part data next start
while [info/2 > length? data] [append data copy client]
write/binary (to-file join "transferred-" (second split-path info/1)) data

insert client "done" wait client close client close port print "Done" halt


REBOL [Title: "Client/Sender"]

ip: "localhost" p: ":8000"  ; IP address and port #
print "sending"

data: read/binary file: to-file request-file
server: open/binary/no-wait rejoin [tcp:// ip p]
insert data append remold [file length? data] #""
insert server data

wait server close server print "Done" halt

Here's a more compact example that demonstrates how to create and send an image from one computer to another:

; server/receiver - run first:

if error? try [port: first wait open/binary/no-wait tcp://:8] [quit]
mark: find file: copy wait port #""
length: to-integer to-string copy/part file mark
while [length > length? remove/part file next mark] [append file port]

view layout [image load file]

; client/sender - run after server (change IP address if using on 2 pcs):

save/png %image.png to-image layout [box blue "I traveled through ports!"]

port: open/binary/no-wait tcp://127.0.0.1:8  ; adjust this IP address
insert file: read/binary %image.png join l: length? file #""
insert port file

The following program is a walkie-talkie push-to-talk type of voice over IP application. It's extremely simple - it just records sound from mic to .wav file, then transfers the wave file to another IP (where the same program is running), for playback. Sender and receiver open in separate processes, and both run in forever loops to enable continuous communication back and forth. As it stands, this is a MS Windows only application. The code which handles the sound recording is discussed in more detail in the section of this tutorial about DLLs:

REBOL [Title: "Intercom (VOIP Messenger)"]

write %wt-receiver.r {
    REBOL []
    print join "Receiving at " read join dns:// read dns://
    if error? try[c: first t: wait open/binary/no-wait tcp://:8000][quit]
    s: open sound://
    forever [
        d: copy wait c
        if error? try [i: load to-string copy/part d start: find d #""] [
            print "^lclient closed" close t close c close s wait 1 quit
        ]
        remove/part d next start
        while [i/2 > length? d] [append d copy c]
        write/binary (to-file join "t-" (second split-path i/1))
            decompress to-binary d
        insert s load %t-r.wav wait s
    ]
}
launch %wt-receiver.r

lib: load/library %winmm.dll
mciExecute: make routine! [c [string!] return: [logic!]] lib "mciExecute"

if (ip: ask "Connect to IP (none = localhost):  ") = "" [ip: "localhost"]
if error? try [s: open/binary/no-wait rejoin [tcp:// ip ":8000"]] [quit]

mciExecute "open new type waveaudio alias buffer1 buffer 4"
forever [
    x: ask "^lPress [ENTER] to start sending sound (or 'q' to quit): "
    if find x "q" [close s  free lib  break]
    ; if (ask "^lPress [ENTER] to send sound ('q' to quit): ") = "q"[quit]
    mciExecute "record buffer1"
    ask "^l*** YOU ARE NOW RECORDING SOUND ***   Press [ENTER] to send:  "
    mciExecute join "save buffer1 " to-local-file %r.wav
    mciExecute "delete buffer1 from 0"
    data: compress to-string read/binary %r.wav
    insert data append remold [%r.wav length? data] #""
    insert s data
]

Here's a more compact version of the above application, with hands-free operation enabled (several obfuscated versions of this script can be found at the end of this tutorial - likely the most compact VOIP programs you'll find anywhere):

REBOL [title: "VOIP"] do [write %ireceive.r {REBOL []
if error? try [port: first wait open/binary/no-wait tcp://:8] [quit]
wait 0  speakers: open sound://
forever [
    if error? try [mark: find wav: copy wait port #""] [quit]
    i: to-integer to-string copy/part wav mark
    while [i > length? remove/part wav next mark] [append wav port]
    insert speakers load to-binary decompress wav
]} launch %ireceive.r
lib: load/library %winmm.dll
mci: make routine! [c [string!] return: [logic!]] lib "mciExecute"
if (ip: ask "Connect to IP (none = localhost):  ") = "" [ip: "localhost"]
if error? try [port: open/binary/no-wait rejoin [tcp:// ip ":8"]] [quit]
mci "open new type waveaudio alias wav"
forever [
    mci "record wav"  wait 2  mci "save wav r"  mci "delete wav from 0"
    insert wav: compress to-string read/binary %r join l: length? wav #""
    if l > 4000 [insert port wav]  ; squelch (don't send) if too quiet
]]

17.6 Transferring Data Through UDP Network Ports

"UDP" is a multicast network protocol used to transmit data to any listening program attached via a network port. Where TCP/IP programs require a server program to have a known IP address, to which all client programs connect, UDP programs simply broadcast messages to an open network port. Any program listening for UDP data on that port can receive the messages. The following program is a perfect example of UDP functionality. There's no need to connect to a central server to exchange messages. Any number of users can connect to a local network and broadcast messages to any/all others who are running this program. This enables a functional office "text intercom" system:

REBOL [Title: "UDP Group Chat Program"]
net-in: open udp://:9905  ; This is UDP, so NO known IP addresses required
net-out: open/lines udp://255.255.255.255:9905
set-modes net-out [broadcast: on]
svv/vid-face/color: white
name: request-text/title "Your name:"
prev-message: ""
gui: view/new layout [
    a1: area wrap rejoin [name ", you are logged in."]  across
    f1: field
    btn "Save Chat" [write request-file/only/save/file %chat.txt a1/text]
    btn "?" [alert "Press [CTRL] + U to see who's online."]
    at 0x0 key #"^M" [
        if f1/text = "" [return]
        insert net-out rejoin [name {, } now/time {:    } f1/text]
    ]
    at 0x0 key #"^u" [
        insert net-out rejoin [name {, } now/time {:    Who's online?}]
    ]
]
forever [
    focus f1
    received: wait [net-in]
    if not viewed? gui [quit]
    if find (message: copy received) "Who's online" [
        insert net-out rejoin [name " is online."]
    ]
    if message <> prev-message [
        insert (at a1/text 1) message show a1
        attempt [
            insert s: open sound:// load %/c/windows/media/ding.wav
            wait s close s
        ]
    ]
    prev-message: copy message
]

The following set of programs are used in the author's music lesson business to alert teachers when their students have arrived for an appointment. UDP is used because any number of teachers can be notified by the central "server" program, and the server program doesn't need to know the IP addresses of any of the potential instructors' computers. It just transmits the messages to whoever is connected and listening:

REBOL [Title: "UDP Signin Client Alarm"]
if error? try [net-in: open udp://:9905] [
    alert {
        This program is already running.  If you want to start a new
        instance, please close the currently open program.  If you have
        any problems, close "rebol" in the task manager or just restart
        your computer.
    }
    quit
]
svv/vid-face/color: white
name: request-list "Your name:" [
    "alex" "brian" "chad" "chris" "david" "dorian" "doug" "emerald"
    "jarrod" "josh" "kevin" "kyle" "lindsey" "mark" "nick" "peter"
    "ryan_gaughan" "stef" "steve"
]
previous-signin: []
attempt [
    insert s: open sound:// load %/c/windows/media/ding.wav
    wait s close s
]
gui: view/new center-face layout [
    a1: area 600x400 wrap rejoin [name ", you are logged in."]
    across
    btn "Save History" [
        write request-file/only/save/file (to-file now/date) a1/text
    ]
    btn "Quit" [quit]
    ; at 0x0 key #"^M" [if a1/text = "" [return]]
]
arrive-sound: load %/c/windows/media/ding.wav
forever [
    received: wait [net-in]
    if not viewed? gui [quit]
    if find (message: copy received) name [
        teacher: first parsed: parse copy message none
        student: at (find/match copy message teacher) 2  ; erase newline
        insert (at a1/text 1) rejoin [
            now/time {, } now/date {:     }
            uppercase teacher ", your student has arrived:   " 
            uppercase student
        ] 
        show a1
        attempt [insert s: open sound:// arrive-sound wait s close s]
    ]
    wait 1
]

This is the server required to run the program above:

REBOL [Title: "UDP Signin Server"]
net-out: open/lines udp://255.255.255.255:9905
set-modes net-out [broadcast: on]
svv/vid-face/color: white
previous-signin: []
write/append %last-signin.txt ""
gui: view/new center-face layout [
    a1: area wrap "Server started"  across
    btn "Quit" [quit]
    ; at 0x0 key #"^M" [if a1/text = "" [return]]
]
forever [attempt [
    if not viewed? gui [quit]
    if previous-signin <> current-signin: load %last-signin.txt [
        insert net-out rejoin [current-signin/1 " " current-signin/2]
        previous-signin: current-signin
        insert (at a1/text 1) rejoin [
            "Last signed in student:  " current-signin/2 newline
            "Last signed in teacher:  " current-signin/1 newline
        ] 
        show a1
        write/append %alarm_history.txt rejoin [
            now 
            {  student: } current-signin/2 
            {  teacher: } current-signin/1 newline
        ]
        attempt [
            insert s: open sound:// load %/c/windows/media/ding.wav
            wait s close s
        ]
    ]
    wait 1
]]
quit
{%last-signin.txt contents should be 2 strings  "nick" "john smith"}

For more information on ports, see http://www.rebol.com/docs/core23/rebolcore-14.html, http://stackoverflow.com/questions/1291127/rebol-smallest-http-server-in-the-world-why-first-wait-listen-port, and http://www.rebol.net/docs/async-ports.html.

17.7 Parse (REBOL's Answer to Regular Expressions)

The "parse" function is used to import and convert organized chunks of external data into the block format that REBOL recognizes natively. It also provides a means of dissecting, searching, comparing, extracting, and acting upon organized information within unformatted text data (similar to the pattern matching functionality implemented by regular expressions in other languages).

The basic format for parse is:

parse <data> <matching rules>

Parse has several modes of use. The simplest mode just splits up text at common delimiters and converts those pieces into a REBOL block. To do this, just specify "none" as the matching rule. Common delimiters are spaces, commas, tabs, semicolons, and newlines. Here are some examples:

text1: "apple orange pear"
parsed-block1: parse text1 none

text2: "apple,orange,pear"
parsed-block2: parse text2 none

text3: "apple        orange                    pear"
parsed-block3: parse text3 none

text4: "apple;orange;pear"
parsed-block4: parse text4 none

text5: "apple,orange pear"
parsed-block5: parse text5 none

text6: {"apple","orange","pear"}
parsed-block6: parse text6 none

text7: {
apple
orange  
pear
}
parsed-block7: parse text7 none

To split files based on some character other than the common delimiters, you can specify the delimiter as a rule. Just put the delimiter in quotes:

text: "apple*orange*pear"
parsed-block: parse text "*"

text: "apple&orange&pear"
parsed-block: parse text "&"

text: "apple    &    orange&pear"
parsed-block: parse text "&"

You can also include mixed multiple characters to be used as delimiters:

text: "apple&orange*pear"
parsed-block: parse text "&*"

text: "apple&orange*pear"
parsed-block: parse text "*&" ; the order doesn't matter

Using the "splitting" mode of parse is a great way to get formatted tables of data into your REBOL programs. Splitting the text below by carriage returns, you run into a little problem:

text: {    First Name
           Last Name
           Street Address
           City, State, Zip}

parsed-block: parse text "^/" 

; ^/ is the REBOL symbol for a carriage return

Spaces are included in the parsing rule by default (parse automatically splits at all empty space), so you get a block of data that's more broken up than intended:

["First" "Name" "Last" "Name" "Street" "Address" "City,"
    "State," "Zip"]

You can use the "/all" refinement to eliminate spaces from the delimiter rule. The code below:

text: {    First Name
           Last Name
           Street Address
           City, State, Zip}

parsed-block: parse/all text "^/"

converts the given text to the following block:

[" First Name" "      Last Name" "      Street Address"
    "      City, State, Zip"]

Now you can trim the extra space from each of the strings:

foreach item parsed-block [trim item]

and you get the following parsed-block, as intended:

["First Name" "Last Name" "Street Address" "City, State, Zip"]

17.8 Using Parse to Load Speadsheet CSV Files and Other Structured Data

Parse is commonly used to convert spreadsheet data into REBOL blocks. In Excel, Open Office, and other spreadsheet programs, you can export all the columns of data in a worksheet by saving it as a CSV formatted ("comma separated value") .csv text file. People often put various bits of descriptive text, labels and column headers into spreadsheets to make them more readable:

;                         TITLE
                       DESCRIPTION

                         Header1 

Category1      data       data      data        Notes...
               data       data      data
               data       data      data
               data       data      data

                         Header2

Category2      data       data      data        Notes...
               data       data      data
               data       data      data
               data       data      data

                         Header3

Category3      data       data      data        Notes...
               data       data      data
               data       data      data
               data       data      data

The following code turns the exported CSV spreadsheet data into a nice useable REBOL block, with group heading data added to each line:

; Read and parse the CSV formatted file:

filename: %filename.csv
data: copy []
lines: read/lines filename
foreach line lines [
    append/only data parse/all line ","
]

; Add headers from sections of the spreadsheet to each line item:

info: copy ""
foreach line data [
    either find "Header" line/1 [
        info: line/1
    ][
        append line info
    ]
]

; Remove the unwanted descriptive header lines:

remove-each line data [find "Header" line/1/1]
remove-each line data [
    (line/3 = "TITLE") or (line/3 = "DESCRIPTION")
]

17.9 Using Parse's Pattern Matching Mode to Search Data

You can use parse to check whether any specific data exists within a given block. To do that, specify the rule (matching pattern) as the item you're searching for. Here's an example:

parse ["apple"] ["apple"]

parse ["apple" "orange"] ["apple" "orange"]

Both lines above evaluate to true because they match exactly. IMPORTANT: By default, as soon as parse comes across something that doesn't match, the entire expression evaluates to false, EVEN if the given rule IS found one or more times in the data. For example, the following is false:

parse ["apple" "orange"] ["apple"]

But that's just default behavior. You can control how parse responds to items that don't match. Adding the words below to a rule will return true if the given rule matches the data in the specified way:

  1. "any" - the rule matches the data zero or more times
  2. "some" - the rule matches the data one or more times
  3. "opt" - the rule matches the data zero or one time
  4. "one" - the rule matches the data exactly one time
  5. an integer - the rule matches the data the given number of times
  6. two integers - the rule matches the data a number of times included in the range between the two integers

The following examples are all true:

parse ["apple" "orange"] [any string!]
parse ["apple" "orange"] [some string!]
parse ["apple" "orange"] [1 2 string!]

You can create rules that include multiple match options - just separate the choices by a "|" character and enclose them in brackets. The following is true:

parse ["apple" "orange"] [any [string! | url! | number!]]

You can trigger actions to occur whenever a rule is matched. Just enclose the action(s) in parentheses:

parse ["apple" "orange"] [any [string! 
    (alert "The block contains a string.") | url! | number!]]

You can skip through data, ignoring chunks until you get to, or past a given condition. The word "to" ignores data UNTIL the condition is found. The word "thru" ignores data until JUST PAST the condition is found. The following is true:

parse [234.1 $50 http://rebol.com "apple"] [thru string!]

The real value of pattern matching is that you can search for and extract data from unformatted text, in an organized way. The word "copy" is used to assign a variable to matched data. For example, the following code downloads the raw HTML from the REBOL homepage, ignores everything except what's between the HTML title tags, and displays that text:

parse read http://rebol.com [
    thru <title> copy parsed-text to </title> (alert parsed-text)
]

The following code extends the example above to provide the useful feature of displaying the external ip address of the local computer. It reads http://guitarz.org/ip.cgi, parses out the title text, and then parses that text again to return only the IP number. The local network address is also displayed, using the built in dns protocol in REBOL:

parse read http://guitarz.org/ip.cgi [
    thru <title> copy my-ip to </title>
]
parse my-ip [
    thru "Your IP Address is: " copy stripped-ip to end
]
alert to-string rejoin [
    "External: " trim/all stripped-ip "  "
    "Internal: " read join dns:// read dns://
]

The following example downloads and parses the current (live) US Dollar exchange rates from http://x-rates.com. The user selects from a list of currencies to convert to, then performs and displays the conversion from USD to the selected currency. The first half of the script is the simple Calculator GUI example taken from the first part of the tutorial. All of the parsing occurs when the "Convert" button is clicked:

REBOL [title: "Currency Rate Conversion Calculator"]
view center-face layout [
    origin 0  space 0x0  across
    f: field 200x40 font-size 20
    return
    style btn btn 50x50 [append f/text face/text  show f]
    btn "1"  btn "2"  btn "3"  btn " + "  return
    btn "4"  btn "5"  btn "6"  btn " - "  return
    btn "7"  btn "8"  btn "9"  btn " * "  return
    btn "0"  btn "."  btn " / "   btn "=" [
        attempt [f/text: form do f/text  show f]
    ] return
    btn 200x35 "Convert" [
        x: copy []
        html: read http://www.x-rates.com/table/?from=USD&amount=1.00
        html: find html "src='/themes/bootstrap/images/xrates_sm_tm.png'" 
        parse html [
            any [
                thru {from=USD} copy link to {</a>} (append x link)
            ] to end 
        ]
        rates: copy []
        foreach rate x [
            parse rate [thru {to=} copy c to {'>}]
            parse rate [thru {'>} copy v to end]
            if not error? try [to-integer v] [append rates reduce [c v]]
        ]  
        currency: request-list "Select Currency:" extract rates 2
        rate: to-decimal select rates currency
        attempt [alert rejoin [currency ": " (rate * to-decimal f/text)]]
    ]
]

Here's a useful example that removes all comments from a given REBOL script (any part of a line that begins with a semicolon ";"):

code: read to-file request-file

parse/all code [any [
    to #";" begin: thru newline ending: (
        remove/part begin ((index? ending) - (index? begin))) :begin
    ]
]

editor code

For more about parse, see the following links:

http://www.codeconscious.com/rebol/parse-tutorial.html
http://www.rebol.com/docs/core23/rebolcore-15.html
http://en.wikibooks.org/wiki/REBOL_Programming/Language_Features/Parse
http://www.rebolforces.com/zine/rzine-1-06.html#sect4.

17.10 Responding to Special Events in a GUI - "Feel"

REBOL's simple GUI syntax makes it easy for widgets to respond to mouse clicks. As you've seen, you can simply put the block of code you want evaluated immediately after the widget that activates it:

view layout [btn "Click me" [alert "Thank you for the click :)"]]

But what if you want your GUI to respond to events other than a mouse click directly on a widget? What if, for example, you want the program to react whenever a user clicks anywhere on the GUI screen (in a paint program, for example), or if you want a widget to do something after a certain amount of time has passed, or if you want to capture clicks on the GUI close button so that the user can't accidentally shut down an important data screen. That's what the "feel" object and "insert-event-func" function are used for.

Here's an example of the basic feel syntax:

view layout [
    text "Click, right-click, and drag the mouse over this text." feel [
        engage: func [face action event] [
            print action
            print event/offset
        ]
    ]
]

The above code is often shortened using "f a e" to represent "face action event":

view layout [
    text "Mouse me." feel [
        engage: func [f a e] [
            print a
            print e/offset
        ]
    ]
]

You can respond to specific events as follows:

view layout [
    text "Mouse me." feel [
        engage: func [f a e] [
            if a = 'up [print "You just released the mouse."]
        ]
    ]
]

This example demonstrates how to combine full screen mouse detection with normal mouse clicks on widgets. To do this, an invisible box the same size as the screen, with a feel event attached, is used for full screen detection. Then, other widgets are simply placed on top of it, starting over at the window origin:

print "Click anywhere in the window, then click the text."
view center-face layout [
    size 400x200
    box 400x200 feel [
        engage: func [f a e] [
            print a
            print e/offset
        ]
    ]
    origin 
    text "Click me" [print "Text clicked"] [print "Text right-clicked"]
    box blue [print "Box clicked"]
]

You can also assign timer events to any widget, as follows:

view layout [
    text "This text has a timer event attached." rate 00:00:00.5 feel [
        engage: func [f a e] [
            if a = 'time [print "1/2 second has passed."]
        ]
    ]
]

Here's a button with a time event attached (a rate of "0" means don't wait at all). Every 0 seconds, when the timer event is detected, the offset (position) of the button is updated. This creates animation:

view layout/size [
    mover: btn rate 0 feel [
        engage: func [f a e] [
            if a = 'time [
                mover/offset: mover/offset + 5x5
                show mover
            ]
        ]
    ]
] 400x400

Here's a little shooting game that uses a timer event to automate the movement of GUI graphics around the screen, check for collisions, and control other game operations:

REBOL [title: "VID Shooter"]
score: 0   speed: 20   fire: false
do game: [
    view center-face layout [
        size 600x440
        at 270x0 text join "Score: " score
        at 280x440 x: box 2x20 yellow
        at (as-pair 0 (random 300) + 30) y: btn 50x20 red "Enemy"
        at 280x420 z: btn 50x20 blue "Player"
        box 0x0 #"l" [z/offset: z/offset + 10x0 show z]
        box 0x0 #"k" [z/offset: z/offset + -10x0 show z]
        box 0x0 #" " [
            if fire = false [
                fire: true 
                x/offset: as-pair z/offset/1 440
            ]
        ]
        box 0x0 rate speed feel [
            engage: func [f a e] [
                if a = 'time [
                    y/offset: y/offset + 5x0
                    if y/offset/1 > 600 [
                        y/offset: as-pair -10 ((random 300) + 30)
                    ]
                    show y
                    if fire = true [x/offset: x/offset + 0x-20]
                    if x/offset/2 < 0 [
                        x/offset/2: 440 
                        fire: false
                    ]
                    show x
                    if within? x/offset y/offset 50x25 [
                        alert "Kablammmm!!!"
                        score: score + 1
                        speed: speed + 5
                        fire: false
                        unview
                        do game
                    ]
                ]
            ]
        ]
    ]
]

By updating the offset of a widget every time it's clicked, you can enable drag-and-drop operations:

view layout/size [
    text "Click and drag this text" feel [
        ; remember f="face", a="action", e="event":
        engage: func [f a e] [
            ; first, record the coordinate at which the mouse is
            ; initially clicked:
            if a = 'down [initial-position: e/offset]
            ; if the mouse is moved while holding down the button, 
            ; move the position of the clicked widget the same amount
            ; (the difference between the initial clicked coordinate
            ; recorded above, and the new current coordinate determined
            ; whenever a mouse move event occurs):
            if find [over away] a [
                f/offset: f/offset + (e/offset - initial-position)
            ]
            show f
        ]
    ]
] 600X440

Feel objects and event functions can be included right inside a style definition. The definition below allows you to easily create multiple GUI widgets that can be dragged around the screen. "movestyle" is defined as a block of code that's later passed to a widget's "feel" object, and is therefore included in the overall style definition (the remove and append functions have been added here to place the moved widget on top of other widgets in the GUI (i.e., to bring the dragged widget to the visual foreground)). You can add this "feel movestyle" code to any GUI widget to make it drag-able:

movestyle: [
    engage: func [f a e] [
        if a = 'down [
            initial-position: e/offset
            remove find f/parent-face/pane f
            append f/parent-face/pane f
        ]
        if find [over away] a [
            f/offset: f/offset + (e/offset - initial-position)
        ]
        show f
    ]
]

view layout/size [
    style moveable-object box 20x20 feel movestyle
    ; "random 255.255.255" represents a different random
    ;  color for each piece:
    at random 600x400 moveable-object (random 255.255.255)
    at random 600x400 moveable-object (random 255.255.255)
    at random 600x400 moveable-object (random 255.255.255)
    at random 600x400 moveable-object (random 255.255.255)
    at random 600x400 moveable-object (random 255.255.255)
    text "This text and all the boxes are movable" feel movestyle
] 600x440

The "detect" function inside a feel block is useful for constantly checking events. The following program constantly checks for mouse movements, and if the mouse is ever positioned over the button, the button is moved to a random position. This technique can be useful, for example, in video games controlled by mouse movement:

view center-face layout [
    size 600x440
    at 270x209 b: btn "Click Me!" feel [
        detect: func [f e] [
            ; The following line checks for any mouse movement:
            if e/type = 'move [
                ; This line checks if the mouse position is within the
                ; coordinates of the button (i.e., touching the button):
                if (within? e/offset b/offset 59x22) [
                    ; If so, move the button to a random position:
                    b/offset: b/offset + ((random 50x50) - (random 50x50))
                    ; Check if the button has been moved off screen:
                    if not within? b/offset -59x-22 659x462 [
                        ; If so, move back to the center of the window:
                        b/offset: 270x209
                    ]
                    ; Update the screen:
                    show b
                ]
            ]
            ; When using the detect function, always return the event:
            e
        ]
    ]
]

To handle global events in a GUI such as resizing and closing, "insert-event-func" is useful. The following example checks for resize events:

insert-event-func [
    either event/type = 'resize [
        alert "I've been resized"
        none   ; return this value when you don't want to
               ; do anything else with the event.
    ][
        event  ; return this value if the specified event
               ; is not found
    ]
]

view/options layout [text "Resize this window."] [resize]

You can use that technique to adjust the window layout, and specifically reposition widgets when a screen is resized:

insert-event-func [
    either event/type = 'resize [
        stay-here/offset:
            stay-here/parent-face/size - stay-here/size - 20x20
        show stay-here
        none   ; return this value when you don't want to
               ; do anything else with the event.
    ][
        event  ; return this value if the specified event
               ; is not found
    ]
]

view/options layout [
    stay-here: text "Resize this window."
] [resize]

To remove an installed event handler, use "remove-event-func". The following example captures three consecutive close events, and then removes the event handler, allowing you to close the GUI on the 4th try:

count: 1
evtfunc: insert-event-func [
    either event/type = 'close [
        if count = 3 [remove-event-func :evtfunc]
        count: count + 1
        none
    ][
        event
    ]
]

view layout [text "Try to close this window 4 times."]

For more information about handling events see http://www.rebol.com/how-to/feel.html, http://www.codeconscious.com/rebol/view-notes.html, and http://www.rebol.com/docs/view-system.html.

17.11 2D Drawing, Graphics, and Animation

With REBOL's "view layout" ("VID") dialect you can easily build graphic user interfaces that include buttons, fields, text lists, images and other GUI widgets, but it's not meant to handle general purpose graphics or animation. For that purpose, REBOL includes a built-in "draw" dialect. Various drawing functions allow you to make lines, boxes, circles, arrows, and virtually any other shape. Fill patterns, color gradients, and effects of all sorts can be easily applied to drawings.

Implementing draw functions typically involves creating a 'view layout' GUI, with a box widget that's used as the viewing screen. "Effect" and "draw" functions are then added to the box definition, and a block is passed to the draw function which contains more functions that actually perform the drawing of various shapes and other graphic elements in the box. Each draw function takes an appropriate set of arguments for the type of shape created (coordinate values, size value, etc.). Here's a basic example of the draw format:

view layout [box 400x400 effect [draw [line 10x39 322x211]]]
;  "line" is a draw function

Here's the exact same example indented and broken apart onto several lines:

view layout [
    box 400x400 effect [
        draw [
            line 10x39 322x211
        ]
    ]
]

Any number of shape elements (functions) can be included in the draw block:

view layout [
    box 400x400 black effect [
        draw [
            line 0x400 400x50
            circle 250x250 100
            box 100x20 300x380
            curve 50x50 300x50 50x300 300x300
            spline closed 3 20x20 200x70 150x200
            polygon 20x20 200x70 150x200 50x300
        ]
    ]
]

Color can be added to graphics using the "pen" function. Shapes can be filled with color, with images, and with other graphic elements using the "fill-pen" function. The thickness of drawn lines is set with the "line-width" function:

view layout [
    box 400x400 black effect [
        draw [
            pen red
            line 0x400 400x50
            pen white
            box 100x20 300x380
            fill-pen green
            circle 250x250 100
            pen blue
            fill-pen orange
            line-width 5
            spline closed 3 20x20 200x70 150x200
            polygon 20x20 200x70 150x200 50x300
        ]
    ]
]

Gradients and other effects can be easily applied to the elements:

view layout [
    box 400x220 effect [
        draw [
            fill-pen 200.100.90
            polygon 20x40 200x20 380x40 200x80
            fill-pen 200.130.110
            polygon 20x40 200x80 200x200 20x100
            fill-pen 100.80.50
            polygon 200x80 380x40 380x100 200x200
        ]
        gradmul 180.180.210 60.60.90
    ]
]

Drawn shapes are automatically anti-aliased (lines are smoothed), but that default feature can be disabled:

view layout [
    box 400x400 black effect [
        draw [
            ;  with default smoothing:
            circle 150x150 100
            ;  without smoothing:
            anti-alias off
            circle 250x250 100
        ]
    ]
]

17.11.1 Animation

Animations can be created with draw by changing the coordinates of image elements. The fundamental process is as follows:

  1. Assign a word label to the box in which the drawing takes place (the word "scrn" is used in the following examples).
  2. Create a new draw block in which the characteristics of the graphic elements (position, size, etc.) are changed.
  3. Assign the new block to "{yourlabel}/effect/draw" (i.e., "scrn/label/draw: [changed draw block]" in this case).
  4. Display the changes with a "show {yourlabel}" function (i.e., "show scrn" in this case).

Here's a basic example that moves a circle to a new position when the button is pressed:

view layout [
    scrn: box 400x400 black effect [draw [circle 200x200 20]]
    btn "Move" [
        scrn/effect/draw: [circle 200x300 20]  ; replace the block above
        show scrn
    ]
]

Variables can be assigned to positions, sizes, and/or other characteristics of draw elements, and loops can be used to create smooth animations by adjusting those elements incrementally:

pos: 200x50
view layout [
    scrn: box 400x400 black effect [draw [circle pos 20]]
    btn "Move Smoothly" [
        loop 50 [
            ; increment the "y" value of the coordinate:
            pos/y: pos/y + 1
            scrn/effect/draw: copy [circle pos 20]
            show scrn
        ]
    ]
]

Animation coordinates (and other draw properties) can also be stored in blocks:

pos: 200x200
coords: [70x346 368x99 143x45 80x125 237x298 200x200]

view layout [
    scrn: box 400x400 black effect [draw [circle pos 20]]
    btn "Jump Around" [
        foreach coord coords [
            scrn/effect/draw: copy [circle coord 20]
            show scrn
            wait 1
        ]
    ]
]

Other data sources can also serve to control movement. In the next example, user data input moves the circle around the screen. Notice the use of the "feel" function to update the screen every 10th of a second ("rate 0:0:0.1"). Since feel is used to watch, wait for, and respond to window events, you'll likely need it in many situations where animation is used, such as in games:

pos: 200x200
view layout [
    scrn: box 400x400 black rate 0:0:0.1 feel [
        engage: func [face action event] [
            if action = 'time [
                scrn/effect/draw: copy []
                append scrn/effect/draw [circle pos 20]
                show scrn
            ]    
        ] 
    ] effect [ draw [] ]
    across
    btn "Up" [pos/y: pos/y - 10]
    btn "Down" [pos/y: pos/y + 10]
    btn "Right" [pos/x: pos/x + 10]
    btn "Left" [pos/x: pos/x - 10]
]

Here's a very simple paint program that also uses the feel function. Whenever a mouse-down action is detected, the coordinate of the mouse event ("event/offset") is added to the draw block (i.e., a new dot is added to the screen wherever the mouse is clicked), and then the block is shown:

view layout [
    scrn: box black 400x400 feel [
        engage: func [face action event] [
            if find [down over] action [
                append scrn/effect/draw event/offset
                show scrn
            ]
            if action = 'up [append scrn/effect/draw 'line]
        ]
    ] effect [draw [line]]
]

A useful feature of draw is the ability to easily scale and distort images simply by indicating 4 coordinate points. The image will be altered to fit into the space marked by those four points:

view layout [
    box 400x400 black effect [
        draw [
            image logo.gif 10x10 350x200 250x300 50x300
            ; "logo.gif" is built into the REBOL interpreter
        ]
    ]
]

Here's an example that incorporates the image scaling technique above with some animation. IMPORTANT: In the following example, the coordinate position calculations occur inside the draw block. Whenever such evaluations occur inside a draw block (i.e., when values are added or subtracted to a variable coordinate position, size, etc.), a "reduce" or "compose" function must be used to evaluate those values. Notice the tick mark (') next to the "image" function. Function words inside a reduced block need to be marked with that symbol to evaluate correctly:

pos: 300x300
view layout [
    scrn: box pos black effect [
        draw [image logo.gif 0x0 300x0 300x300 0x300]
    ]
    btn "Animate" [
        for point 1 140 1 [
            scrn/effect/draw: copy reduce [
                'image logo.gif 
                (pos - 300x300)
                (1x1 + (as-pair 300 point))
                (pos - (as-pair 1 point))
                (pos - 300x0)
            ]
            show scrn
        ]
        for point 1 300 1 [
            scrn/effect/draw: copy reduce [
                'image logo.gif 
                (1x1 + (as-pair 1 point))
                (pos - 0x300)
                (pos - 0x0)
                (pos - (as-pair point 1))
            ]
            show scrn
        ]
        ; no "reduce" is required below, because no calculations
        ; occur in the draw block - they're just static coords: 
        scrn/effect/draw: copy [
            image logo.gif 0x0 300x0 300x300 0x300
        ]
        show scrn
    ]
]

Here's another example of a draw block which contains evaluated calculations, and therefore requires "reduce"d evaluation:

view layout [
    scrn: box 400x400 black effect [draw [line 0x0 400x400]]
    btn "Spin" [
        startpoint: 0x0
        endpoint: 400x400
        loop 400 [
            scrn/effect/draw: copy reduce [
                'line 
                startpoint: startpoint + 0x1
                endpoint: endpoint - 0x1
            ]
            show scrn
        ]
    ]
]

The useful little paint program at http://rebol.org/cgi-bin/cgiwrap/rebol/view-script.r?script=paintplus.r consists of only 238 lines of code. Take a look at it to see how efficient REBOL's draw code is:

url: http://rebol.org/cgi-bin/cgiwrap/rebol/download-a-script.r?
script: "script-name=paintplus.r"
do rejoin [url script]
paint none []

The paint program above is actually a really useful tool. You can load images on which to paint, and save edits to be reloaded later:

paint load %myimage.png load %edits.txt

Take a look at the 100 draw examples script to see many more bits of useful draw code.

For more information about built-in shapes, functions, and capabilities of draw, see http://www.rebol.com/docs/draw-ref.html, http://www.rebol.com/docs/draw.html, http://translate.google.com/translate?hl=en&sl=fr&u=http://www.rebolfrance.info/org/articles/login11/login11.htm (translated by Google), http://www.rebolforces.com/zine/rzine-1-05.html, http://www.rebolforces.com/zine/rzine-1-06.html (updated code for these two tutorials is available at http://mail.rebol.net/maillist/msgs/39100.html). A nice, short tutorial demonstrating how to build multi-player, networked games with draw graphics is available at RebolFrance (translated by Google). Also be sure to see http://www.nwlink.com/~ecotope1/reb/easy-draw.r (a clickable rebsite version is available in the REBOL Desktop -> Docs -> Easy Draw).

17.12 3D Graphics with r3D

The "r3D" modeling engine by Andrew Hoadley is built entirely from native REBOL 2D draw functions. It demonstrates the significantly powerful potential of draw. It was demonstrated earlier in the tutorial with useful a 3D plotting script. The examples below show some more of what you can accomplish with r3D:

do http://www.rebol.net/demos/BF02D682713522AA/i-rebot.r
do http://www.rebol.net/demos/BF02D682713522AA/histogram.r
do http://www.rebol.net/demos/BF02D682713522AA/objective.r

The r3D engine is small. Here's the entire module in compressed, embeddable format (this is all just standard REBOL code compressed into a more compact format). To enable 3D graphics in your REBOL programs, just include this text in your code (paste it, or "do" it from a file). If you'd like to read and learn from the pure REBOL code that makes up this module, see the examples above (the r3D module is included in those examples as regular text code):

do to-string decompress 64#{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}

Here's a simple example that demonstrates the basic syntax and use of r3D. Be sure to do the code above before running this example:

Transx:  Transy:  Transz: 300.0          ; Set some camera
Lookatx:  Lookaty:  Lookatz: 100.0       ; positions to
                                         ; start with.
do update: does [            ; This "update" function is where
    world: copy []           ; everything is defined.
    append world reduce [    ; Add your 3D objects inside this "append".
        reduce [cube-model (r3d-scale 100.0 150.0 125.0) red]
    ]                        ; A red 'cube' 100x150x125 pixels is added.
    camera: r3d-position-object   
        reduce [Transx Transy Transz]
        reduce [Lookatx Lookaty Lookatz]
        [0.0 0.0 1.0] 
    RenderTriangles: render world camera r3d-perspective 250.0 400x360
    probe RenderTriangles    ; This line demonstrates what's going on
]                            ; under the hood.  You can eliminate it.

view layout [
    scrn: box 400x360 black effect [draw RenderTriangles]  ; basic draw
    across return
    slider 60x16 [Transx: (value * 600 - 300.0) update show scrn]
    slider 60x16 [Transy: (value * 600 - 300.0) update show scrn]
    slider 60x16 [Transz: (value * 600) update show scrn]
    slider 60x16 [Lookatx: (value * 400 - 200.0) update show scrn]
    slider 60x16 [Lookaty: (value * 400 - 200.0) update show scrn]
    slider 60x16 [Lookatz: (value * 200 ) update show scrn]
]

R3D works by rendering 3D images to native REBOL 2D draw functions, which are contained in the "RenderTriangles" block above. R3D provides basic shape structures and a simple language interface to create and view those images in a REBOL application. It automatically adjusts lighting and other characteristics of images as they're viewed from different perspectives. To see how the rendering of images is converted into simple REBOL draw functions, watch the output of the "probe RenderTriangles" line in the REBOL interpreter as you adjust the sliders above. It displays the list of draw commands used to create each image in the moving 3D world.

In the example above, slider widgets are used to adjust values in the animation. Those values could just as easily be controlled by loops or other forms of data input. In the example below, the values are adjusted by keystrokes assigned to empty text widgets (use the "asdfghqwerty" keys to move the cube):

Transx:  Transy:  Transz: 2.0
Lookatx:  Lookaty:  Lookatz: 1.0 
do update: does [
    world: copy []
    append world reduce [ 
        reduce [cube-model (r3d-scale 100.0 150.0 125.0) red]
    ]
    Rendered: render world 
        r3d-position-object   
        reduce [Transx Transy Transz]
        reduce [Lookatx Lookaty Lookatz]
        [0.0 0.0 1.0]
        r3d-perspective 360.0 400x360
]
view layout [
    across
    text "" #"a" [Transx: (Transx + 10) update show scrn]
    text "" #"s" [Transx: (Transx - 10) update show scrn]
    text "" #"d" [Transy: (Transy + 10) update show scrn]
    text "" #"f" [Transy: (Transy - 10) update show scrn]
    text "" #"g" [Transz: (Transz + 10) update show scrn]
    text "" #"h" [Transz: (Transz - 10) update show scrn]
    text "" #"q" [Lookatx: (Lookatx + 10) update show scrn]
    text "" #"w" [Lookatx: (Lookatx - 10) update show scrn]
    text "" #"e" [Lookaty: (Lookaty + 10) update show scrn]
    text "" #"r" [Lookaty: (Lookaty - 10) update show scrn]
    text "" #"t" [Lookatz: (Lookatz + 10) update show scrn]
    text "" #"y" [Lookatz: (Lookatz - 10) update show scrn]
    at 20x20
    scrn: box 400x360 black effect [draw Rendered] 
]

The r3D module can work with models saved in native .R3d format, and the "OFF" format (established by the GeomView program at http://www.geom.uiuc.edu/projects/visualization/. See http://local.wasp.uwa.edu.au/~pbourke/dataformats/oogl/#OFF for a description of the OFF file format). A number of OFF example objects are available at http://www.mpi-sb.mpg.de/~kettner/proj/obj3d/.

To understand how to create/import and manipulate more complex 3D shapes, examine the way objects are designed inside the "update" function in each of Andrew's three examples. Here's a simplified variation of Andrew's objective.r example that loads .off models from the hard drive. Be sure to do the r3D module code above before running this example, and then try downloading and loading some of the example .off files at the web site above:

RenderTriangles: []
view layout [
    scrn: box 400x360 black effect [draw RenderTriangles]
    across return
    slider 60x16 [Transx: (value * 600 - 300.0) update show scrn]
    slider 60x16 [Transy: (value * 600 - 300.0) update show scrn]
    slider 60x16 [Transz: (value * 600) update show scrn]
    slider 60x16 [Lookatx: (value * 400 - 200.0) update show scrn]
    slider 60x16 [Lookaty: (value * 400 - 200.0) update show scrn]
    slider 60x16 [Lookatz: (value * 200 ) update show scrn]
    return btn "Load Model" [
        model: r3d-load-OFF load to-file request-file
        modelsize: 1.0
        if model/3 [modelsize: model/3]
        if modelsize < 1.0 [ modelsize: 1.0 ]
        defaultScale: 200.0 / modelsize
        objectScaleX: objectScaleY: objectScaleZ: defaultscale
        objectRotateX: objectRotateY: objectRotateZ: 0.0
        objectTranslateX: objectTranslateY: objectTranslateZ: 0.0    
        Transx:  Transy:  Transz: 300.0
        Lookatx:  Lookaty:  Lookatz: 200.0
        modelWorld: r3d-compose-m4 reduce [
            r3d-scale objectScaleX objectScaleY objectScaleZ
            r3d-translate 
                objectTranslateX objectTranslateY objectTranslateZ
            r3d-rotatex objectRotateX
            r3d-rotatey objectRotateY 
            r3d-rotatez objectRotateZ
        ]
        r3d-object: reduce [model modelWorld red]
        do update: does [
            world: copy []    
            append world reduce [r3d-object]
            camera: r3d-position-object   
                reduce [Transx Transy Transz]
                reduce [Lookatx Lookaty Lookatz]
                [0.0 0.0 1.0] 
            RenderTriangles: 
                render world camera r3d-perspective 250.0 400x360
        ]
        update show scrn
    ]
]

Like most REBOL solutions, r3D is a brilliantly simple, compact, and powerful design that doesn't require any external toolkits. It's pure REBOL, and it's really amazing!

17.13 Several 3D Scripts Using Raw REBOL Draw Dialect

The following short script is a compacted version of Gregory Pecheret's "ebuc-cube" (from http://www.rebol.net/demos/download.html). It demonstrates some simple 3d techniques using only native REBOL draw functions (no 3rd party library required). It's relatively easy to understand, manipulate, and use to create your own basic 3D graphics:

z: 10 h: z * 12 j: negate h c: as-pair z * 5 z * 5 l: z * 4 w: z * 20
img: to-image layout [box effect [draw [pen logo.gif circle c l]]]
q: make object! [x: 0 y: 0 z: 0] 
cube: [[h h j] [h h h] [h j j] [h j h] [j h j] [j h h] [j j j] [j j h]]
view center-face layout [
    f: box 400x400 rate 0 feel [engage: func [f a e] [
        b: copy []   q/x: q/x + 5   q/y: q/y + 8   q/z: q/z + 3
        repeat n 8 [
            p: reduce pick cube n  ; point
            zx: (p/1 * cosine q/z) - (p/2 * sine q/z) - p/1
            zy: (p/1 * sine q/z) + (p/2 * cosine q/z) - p/2
            yx: (p/1 + zx * cosine q/y) - (p/3 * sine q/y) - p/1 - zx
            yz: (p/1 + zx * sine q/y) + (p/3 * cosine q/y) - p/3
            xy: (p/2 + zy * cosine q/x) - (p/3 + yz * sine q/x) - p/2 - zy
            append b as-pair (p/1 + yx + zx + w) (p/2 + zy + xy + w)
        ]
        f/effect: [draw [
            fill-pen 255.0.0.100  polygon b/6 b/2 b/4 b/8
            image img b/6 b/5 b/1 b/2 
            fill-pen 255.159.215.100  polygon b/2 b/1 b/3 b/4 
            fill-pen 54.232.255.100 polygon b/1 b/5 b/7 b/3 
            fill-pen 0.0.255.100 polygon b/5 b/6 b/8 b/7 
            fill-pen 248.255.54.100 polygon b/8 b/4 b/3 b/7
        ]]
        show f
    ]]
]

Here's a version that reshapes and moves the 3D cube in, out and around the screen:

g: 12 i: 5 h: i * g j: negate h w: 0 v2: v1: 1  ; sizes/positions
img: to-image layout [box 200.200.200.50 center logo.gif]
q: make object! [x: 0 y: 0 z: 0]
cube: [[h h j] [h h h] [h j j] [h j h] [j h j] [j h h] [j j j] [j j h]]
view center-face layout/tight [
    f: box 500x450 rate 0 feel [engage: func [f a e] [
        b: copy []  q/x: q/x + 3 q/y: q/y + 3 ; q/z: q/z + 3  ; spinning
        repeat n 8 [
            if w > 500 [v1: 0]   ; w: xy pos        v1: xy direction
            if w < 0 [v1: 1]
            either v1 = 1 [w: w + 1] [w: w - 1]
            if j > (g * i * 2) [v2: 0]  ; j: z pos (size) v2: z direction
            if j < g [v2: 1]
            either v2 = 1 [h: h - 1] [h: h + 1]  j: negate h
            p: reduce pick cube n  ; point
            zx: p/1 * cosine q/z - (p/2 * sine q/z) - p/1
            zy: p/1 * sine q/z + (p/2 * cosine q/z) - p/2
            yx: (p/1 + zx * cosine q/y) - (p/3 * sine q/y) - p/1 - zx
            yz: (p/1 + zx * sine q/y) + (p/3 * cosine q/y) - p/3
            xy: (p/2 + zy * cosine q/x) - (p/3 + yz * sine q/x) - p/2 - zy
            append b as-pair (p/1 + yx + zx + w) (p/2 + zy + xy + w)
        ]
        f/effect: [draw [
            image img b/6 b/5 b/1 b/2 
            fill-pen 255.0.0.50      polygon b/6 b/2 b/4 b/8
            fill-pen 255.159.215.50  polygon b/2 b/1 b/3 b/4 
            fill-pen 54.232.255.50   polygon b/1 b/5 b/7 b/3 
            fill-pen 0.0.255.50      polygon b/5 b/6 b/8 b/7 
            fill-pen 248.255.54.50   polygon b/8 b/4 b/3 b/7
        ]]
        show f
    ]]
]

And here's a little 3D game, with sound, based on the above code:

REBOL [title: "Little 3D Game"]

beep-sound: load to-binary decompress 64#{
eJwBUQKu/VJJRkZJAgAAV0FWRWZtdCAQAAAAAQABABErAAARKwAAAQAIAGRhdGEl
AgAA0d3f1cGadFQ+T2Z9jn1lSjM8T2uNsM/j7Midc05PWGh4eXVrXE5DQEZumsTn
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fXNkUkdCRlN7ps3r3cSkgm1fWFhmdH2AaVA6LElwnMja4dzNpHtXPUxje45/aVA5
PUtif6TG3uvMpHtXU1lkcnd2cGVURT0+ZJC84+HUvaGCZ1NIWm6AinVaQCtAX4Wu
yt3k37aJYEBKXXOHf3FdSEJET2KJsdPr1reUcGJbW2FsdXl2YUs5MFF7qdPe3tO+
mHNUP1Bnfo59ZEkyPFFukbTR5OvGm3BMTVlpent1aVpMQ0FJcZ3I6uHMsJB2YlZR
YXJ/hW5UOypEaJK90+Dg1qyBWjxKYHeLgG1WPz9HWXKYvNnr0KyFYVhZX2pydnVu
Wkc7N1yHtN3h2sivjGxTRFZrgI15X0MtPVh7osHZ5ua+kmdES1tvgn5zY1BGQ0hW
fqjO69vBoX9rXllaaHV9fmhPOi1Lcp/K2+DayaF4Vj1NY3uNfmhONjxLZIKnyODr
yqJ4VFFYZHN3dm5iUUM9QGaTv+Th0rqdf2VTSltvgIl0WT4rQGCIssze5N60iF8/
Sl10h39vW0ZBRFFljLPU69W1kG1gWlxiYHkWb1ECAAA=
}
alert {
   Try to click the bouncing REBOLs as many times as possible in
   30 seconds.  The speed increases with each click!
}
do game: [
   speaker: open sound://
   g: 12 i: 5 h: i * g j: negate h  x: y: z: w: sc: 0  v2: v1: 1  o: now
   img1: to-image layout [backcolor brown box red center logo.gif]
   img2: to-image layout [backcolor aqua box yellow center logo.gif]
   img3: to-image layout [backcolor green box tan center logo.gif]
   cube: [[h h j][h h h][h j j][h j h][j h j][j h h][j j j][j j h]]
   view center-face layout/tight [
      f: box white 550x550 rate 15 feel [engage: func [f a e] [
         if a = 'time [
            b: copy []  x: x + 3  y: y + 3  ; z: z + 3
            repeat n 8 [
               if w > 500 [v1: 0]   if w < 50 [v1: 1]
               either v1 = 1 [w: w + 1] [w: w - 1]
               if j > (g * i * 1.4) [v2: 0]   if j < 1 [v2: 1]
               either v2 = 1 [h: h - 1] [h: h + 1]  j: negate h
               p: reduce pick cube n 
               zx: p/1 * cosine z - (p/2 * sine z) - p/1
               zy: p/1 * sine z + (p/2 * cosine z) - p/2
               yx: (p/1 + zx * cosine y) - (p/3 * sine y) - p/1 - zx
               yz: (p/1 + zx * sine y) + (p/3 * cosine y) - p/3
               xy: (p/2 + zy * cosine x) - (p/3 + yz * sine x) - p/2 - zy
               append b as-pair (p/1 + yx + zx + w) (p/2 + zy + xy + w)
            ]
            f/effect: [draw [
               image img1 b/6 b/2 b/4 b/8
               image img2 b/6 b/5 b/1 b/2
               image img3 b/1 b/5 b/7 b/3 
            ]]
            show f
            if now/time - o/time > :00:20 [
               close speaker
               either true = request [
                  join "Time's Up! Final Score: " sc "Again" "Quit"
               ] [do game] [quit]
            ]
         ]
         if a = 'down [
            xblock: copy [] yblock: copy []
            repeat n 8 [
                append xblock first pick b n
                append yblock second pick b n
            ]
            if all [
                e/offset/1 >= first minimum-of xblock
                e/offset/1 <= first maximum-of xblock
                e/offset/2 >= first minimum-of yblock
                e/offset/2 <= first maximum-of yblock
            ][
               insert speaker beep-sound wait speaker
               sc: sc + 1
               t1/text: join "Score: " sc 
               show t1
               if (modulo sc 3) = 0 [f/rate: f/rate + 1]
               show f
            ]
         ]
      ]]
      at 200x0 t1: text brown "Click the bouncing REBOLs!"
   ]
]

17.14 Sprite Sheets

"Sprite sheets" are large images that consist of many smaller images, each intended to be used independently. Here's an example that demonstrates how to crop and use individual images from sprite sheets (in this case, random images from a sheet of smileys):

REBOL [title: "Random Smileys 'Sprite Sheet'"] code: [
rows: 4   cols: 3   x: 64  y: 64   random/seed now 
update-pic: does [
    z: as-pair (random rows) * x - x (random cols) * y - y
    img/effect: [crop z]  show img
]
view layout [
   backdrop white
   img: image 61x61 pic #"^M" [update-pic]
]]
pic: load to-binary decompress 64#{
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AJECvNrcU4oqWZJr/9l+BsVcgFoAAA==
}
do code

17.15 Multitasking

"Threads" are a feature of modern operating systems that allow multiple pieces of code to run concurrently, without waiting for the others to complete. Without threads, individual portions of code must be evaluated in consecutive order. Unfortunately, REBOL does not implement a formal mechanism for threading at the OS level, but does contain built-in support for asynchronous network port and services activity. See http://www.rebol.net/docs/async-ports.html, http://www.rebol.net/docs/async-examples.html, http://www.rebol.net/rebservices/services-start.html, and http://www.rebol.net/rebservices/quick-start.html for more information.

The following technique provides an alternate way to evaluate other types of code in a multitasking manner:

  1. Assign a rate of 0 to a GUI item in a 'view layout' block.
  2. Assign a "feel" detection to that item, and put the actions you want performed simultaneously inside the block that gets evaluated every time a 'time event occurs.
  3. Stop and start the evaluation of concurrently active portions of code by assigning a rate of "none" or 0, respectively, to the associated GUI item.

The following is an example of a webcam viewer which creates a video stream by repeatedly downloading and displaying images from a given webcam URL. To create a moving video effect, the process of downloading each image must run without stopping (i.e., in some sort of unending "forever" loop). But for a user to control the stop/start of the video flow (by clicking a button, for example), the interpreter must be able to check for user events that occur outside the forever loop. By running the repeated download using the technique outlined above, the program can continue to respond to other events while continuously looping the download code:

webcam-url: http://209.165.153.2/axis-cgi/jpg/image.cgi
view layout [
    btn "Start Video" [
        webcam/rate: 0 
        webcam/image: load webcam-url 
        show webcam
    ]
    btn "Stop Video" [webcam/rate: none show webcam]
    return 
    webcam: image load webcam-url 320x240 rate 0 feel [
        engage: func [face action event][
            if action = 'time [
                face/image: load webcam-url show face
            ] 
        ] 
    ]
]

Here's an example in which two webcam video updates are treated as separate processes. Both can be stopped and started as needed:

webcam-url: http://209.165.153.2/axis-cgi/jpg/image.cgi
view layout [
    across 
    btn "Start Camera 1" [
        webcam/rate: 0 
        webcam/image: load webcam-url 
        show webcam
    ]
    btn "Stop Camera 1" [webcam/rate: none show webcam]
    btn "Start Camera 2" [
        webcam2/rate: 0 
        webcam2/image: load webcam-url 
        show webcam2
    ]
    btn "Stop Camera 2" [webcam2/rate: none show webcam2]
    return 
    webcam: image load webcam-url 320x240 rate 0 feel [
        engage: func [face action event][
            if action = 'time [
                face/image: load webcam-url show face
            ] 
        ] 
    ]
    webcam2: image load webcam-url 320x240 rate 0 feel [
        engage: func [face action event][
            if action = 'time [
                face/image: load webcam-url show face
            ] 
        ] 
    ] 
]

Unfortunately, this technique is not asynchronous. Each piece of event code is actually executed consecutively, in an alternating pattern, instead of simultaneously. Although the effect is similar (even indistinguishable) in many cases, the evaluation of code is not concurrent. For example, the following example adds a time display to the webcam viewer. You'll see that the clock is not updated every second. That's because the image download code and the clock code run alternately. The image download must be completed before the clock's 'time action can be evaluated. Try stopping the video to see the difference:

webcam-url: http://209.165.153.2/axis-cgi/jpg/image.cgi
view layout [
    btn "Start Video" [
        webcam/rate: 0 
        webcam/image: load webcam-url 
        show webcam
    ]
    btn "Stop Video" [webcam/rate: none show webcam]
    return 
    webcam: image load webcam-url 320x240 rate 0 feel [
        engage: func [face action event][
            if action = 'time [
                face/image: load webcam-url show face
            ] 
        ] 
    ]
    clock: field to-string now/time/precise rate 0 feel [
        engage: func [face action event][
            if action = 'time [
                face/text: to-string now/time/precise show face
            ] 
        ] 
    ]
]

One solution to achieving truly asynchronous activity is to simply write the code for one process into a separate file and run it in a separate REBOL interpreter process using the "launch" function:

write %async.r {
    REBOL []
    view layout [
        clock: field to-string now/time/precise rate 0 feel [
            engage: func [face action event][
                if action = 'time [
                    face/text: to-string now/time/precise show face
                ] 
            ] 
        ]
    ]
}

launch %async.r
; REBOL will NOT wait for the evaluation of code in async.r
; to complete before going on:

webcam-url: http://209.165.153.2/axis-cgi/jpg/image.cgi
view layout [
    btn "Start Video" [
        webcam/rate: 0 
        webcam/image: load webcam-url 
        show webcam
    ]
    btn "Stop Video" [webcam/rate: none show webcam]
    return 
    webcam: image load webcam-url 320x240 rate 0 feel [
        engage: func [face action event][
            if action = 'time [
                face/image: load webcam-url show face
            ]
        ]
    ]
]

The technique above simply creates two totally separate REBOL programs from within a single code file. If such programs need to interact, share data, or respond to interactive activity states, they can communicate via tcp network port, or by reading/writing data via a shared storage device.

17.16 Using DLLs and Shared Code Files in REBOL

"Dll"s in Windows, "So" files in Linux, and "Dylib" on Macs are libraries of functions that can be shared among different programming languages. Shared code libraries are used to extend the capabilities of a language with new functions. They allow you to accomplish goals which aren't possible (or which are otherwise complicated) using the native functions built into the language. Most of the executable code, and all the potential capabilities, of most operating systems is contained in such files. Third party code libraries are also available to make easy work of complex tasks such as multimedia programming, 3d game programming, specialized hardware control, etc. To use Dlls and shared code files in REBOL, you'll need to download version 2.76 or later of the REBOL interpreter (rebview.exe). If you're using any of the beta versions from http://www.rebol.net/builds/, use either rebview.exe or rebcmdview.exe to run the examples in this section.

Using the format below, you can access and use the functions contained in most DLLs, as if they're native REBOL functions:

lib: load/library %TheNameOfYour.DLL

; "TheFunctionNameInsideTheDll" is loaded from the Dll and converted
; into a new REBOL function called "your-rebol-function-name":

your-rebol-function-name: make routine! [
    return-value: [data-type!]
    first-parameter [data-type!] 
    another-parameter [data-type!] 
    more-parameters [and-their-data-types!]
    ...
] lib "TheFunctionNameInsideTheDll"

; When the new REBOL function is used, it actually runs the function
; inside the Dll:

your-rebol-function-name parameter1 parameter2 ...

free lib

The first line opens access to the functions contained in the specified Dll. The following lines convert the function contained in the Dll to a format that can be used in REBOL. To make the conversion, a REBOL function is labeled and defined (i.e, "your-rebol-function-name" above), and a block containing the labels and types of parameters used and values returned from the function must be provided ("[return: [integer!]]" and "first-parameter [data-type!] another-parameter [data-type!] more-parameters [and-their-data-types!]" above). The name of the function, as labeled in the Dll, must also be provided immediately after the parameter block ("TheFunctionNameInsideTheDll" above). The second to last line above actually executes the new REBOL function, using any appropriate parameters you choose. When you're done using functions from the Dll, the last line is used to free up the Dll so that it's closed by the operating system.

Here are some examples:

REBOL []

; The "kernel32.dll" is a standard dll in all Windows installations:

lib: load/library %kernel32.dll

; The "beep" function is contained in the kernel32.dll library.
; We'll create a new REBOL function called "play-sound" that
; actually executes the "beep" function in kernel32.dll.  The
; "beep" function takes two integer parameters (pitch and 
; duration values), and returns an integer value:

play-sound: make routine! [
    return: [integer!] pitch [integer!] duration [integer!]
] lib "Beep"

; (Beep returns a value of zero if the function does not complete
; successfully.  Otherwise it returns a nonzero number).

; Now we can use the "play-sound" function AS IF IT'S A NATIVE
; REBOL FUNCTION:

for hertz 37 3987 50 [
    print rejoin ["The pitch is now " hertz " hertz."]
    play-sound hertz 50
]

free lib
halt

The following example demonstrates how to record sounds (with the microphone attached to your computer) using the Windows MCI API. When complete, the recorded sound is played back using a native REBOL sound port:

; Various mci functions are included in the winmm.dll library.
; We'll create a new REBOL function called "mciExecute" that
; allows us to run MCI functions in winmm.dll.  This function
; function takes one string parameter (a text string written 
; in MCI function syntax), and returns an integer value (true
; if the function is successful, false if it fails):

lib: load/library %winmm.dll
mciExecute: make routine! [ 
    command [string!]
    return: [logic!] 
] lib "mciExecute"

; Get a file name from the user, which will be used to save the
; recorded sound:

file: to-local-file to-file request-file/save/title/file "Save as:" {
    } %rebol-recording.wav

; Open an MCI buffer and begin the recording:

mciExecute "open new type waveaudio alias buffer1 buffer 6"
mciExecute "record buffer1"

ask "RECORDING STARTED (press [ENTER] when done)...^/"

; Stop recording and save the sound to the wave file selected above:

mciExecute "stop buffer1"
mciExecute join "save buffer1 " file

; Close the DLL:

free lib

print "Recording complete.  Here's how it sounds:^/"

; Play back the sound:

insert port: open sound:// load to-rebol-file file wait port close port
print "DONE.^/"

halt

The next example demonstrates how to play AVI video files, again using the Windows API "mciExecute" from winmm.dll. A demo video is downloaded from the Internet and played two times - once with default settings, and a second time at a given location on screen at twice the original recorded speed. The video codec in the demo video is MS-CRAM (Microsoft Video 1), and the audio format is PCM. For more information about mciExecute commands, Google "multimedia command strings" and see http://msdn.microsoft.com/en-us/library/dd743572(VS.85).aspx:

; These lines open the winmm.dll and define the "mciExecute" function
; in REBOL:

lib: load/library %winmm.dll
mciExecute: make routine! [c [string!] return: [logic!]] lib "mciExecute"

; These lines download a demo video:

if not exists? %test.avi [
    flash "Downloading test video..."
    write/binary %test.avi read/binary http://re-bol.com/test.avi
    unview
]
video: to-local-file %test.avi

; The lines run the mciExecute function with the commands needed to
; play the video:

mciExecute rejoin ["OPEN " video " TYPE AVIVIDEO ALIAS thevideo"]
mciExecute "PLAY thevideo WAIT"
mciExecute "CLOSE thevideo"

mciExecute rejoin ["OPEN " video " TYPE AVIVIDEO ALIAS thevideo"]
mciExecute "PUT thevideo WINDOW AT 200 200 0 0"  ; at 200x200
mciExecute "SET thevideo SPEED 2000"  ; play twice a fast
mciExecute "PLAY thevideo WAIT"
mciExecute "CLOSE thevideo"

; These lines clean up:

free lib
quit

The next example uses the "dictionary.dll" from http://www.reelmedia.org/pureproject/archive411/dll/Dictionary.zip to perform a spell check on text entered at the REBOL command line. There are two functions in the dll that are required to perform a spell check - "Dictionary_Load" and "Dictionary_Check":

REBOL []

check-me: ask "Enter a word to be spell-checked:  "

lib: load/library %Dictionary.dll

; Two new REBOL functions are created, which actually run the
; Dictionary_Load and Dictionary_Check functions in the DLL:

load-dic: make routine! [
    a [string!] 
    return: [none]
] lib "Dictionary_Load"

check-word: make routine! [
    a [string!]
    b [integer!]
    return: [integer!]
] lib "Dictionary_Check"

; This line runs the Dictionary_Load function from the DLL:

load-dic ""

; This line runs the Dictionary_Check function in the DLL, on
; whatever text was entered into the "check-me" variable above:

response: check-word check-me 0

; The Dictionary_Check function returns 0 if there are no errors:

either response = 0 [
    print "No spelling errors found." 
] [
    print "That word is not in the dictionary."
]

free lib
halt

The following example plays an mp3 sound file using the Dll at http://musiclessonz.com/mp3.dll. Of course, that Dll could be compressed and embedded in the code to eliminate the necessity of downloading the file:

REBOL []

write/binary %mp3.dll read/binary http://musiclessonz.com/mp3.dll
lib: load/library %mp3.dll

; the "playfile" function is loaded from the Dll, and converted
; to a new REBOL "play-mp3" function:

play-mp3: make routine! [a [string!] return: [none]] lib "playfile"

; Then an mp3 file name is requested from the user, which is played
; by the "playfile" function in the Dll:

file: to-local-file to-string request-file
play-mp3 file

print "Done playing, Press [Esc] to quit this program: "
free lib

The next example uses the "AU3_MouseMove" function from the Dll version of AutoIt, to move the mouse around the screen. AutoIt contains a wide variety of functions to programatically push buttons, type text, select menu items, choose items from lists, control the mouse, etc. in any existing program window, as if those actions had been performed by a user clicking and typing on screen. Learning the other functions in the AutoIt language can be very helpful in customizing and automating existing Windows applications:

REBOL []

if not exists? %AutoItDLL.dll [
    write/binary %AutoItDLL.dll
    read/binary http://musiclessonz.com/rebol_tutorial/AutoItDLL.dll
]

lib: load/library %AutoItDLL.dll
move-mouse: make routine! [
    return: [integer!] x [integer!] y [integer!] z [integer!]
] lib "AUTOIT_MouseMove"

print "Press the [Enter] key to see your mouse move around the screen."
print "It will move to the top corner, and then down diagonally to"
ask "position 200x200:  " 

for position 0 200 5 [
    move-mouse position position 10 
    ; "10" refers to the speed of the mouse movement
]

free lib
print "^/Done.^/"
halt

This example uses Dll functions from the native Windows API to eliminate the default 'REBOL - ' text at the top of the GUI window:

REBOL []

; First, load the necessary dll:

user32.dll: load/library %user32.dll

; Then define the Windows API functions you'll need:

get-focus: make routine! [return: [int]] user32.dll "GetFocus"

set-caption: make routine! [
    hwnd [int] 
    a [string!]  
    return: [int]
] user32.dll "SetWindowTextA"

; Next, create your GUI - be sure to use 'view/new', so that it doesn't
; appear immediately (start the GUI later with 'do-events', after you've
; changed the title bar below):

view/new center-face layout [
    backcolor white
    text bold "Notice that there's no 'Rebol - ' in the title bar above."
    text "New title text:" 
    across
    f: field "Tada!"
    btn "Change Title" [
        ; These functions change the text in the title bar:
        hwnd: get-focus
        set-caption hwnd f/text
    ]
    btn "Exit" [
        ; Be sure to close the dll when you're done:
        free user32.dll
        quit
    ]
]

; Once you've created your GUI, run the Dll functions to replace the
; default text in the title bar:

hwnd: get-focus
set-caption hwnd "My Title"

; Finally, start your GUI:

do-events

Here's a slightly more versatile version of the above script. You can add it to the top of any existing GUI script, and it will remove the default "REBOL -" text from all GUI title bars, including alerts and requestors:

title-text: "My Program"
if system/version/4 = 3 [
    user32.dll: load/library %user32.dll
    get-tb-focus: make routine! [return: [int]] user32.dll "GetFocus"
    set-caption: make routine! [
        hwnd [int] 
        a [string!]  
        return: [int]
    ] user32.dll "SetWindowTextA"
    show-old: :show
    show: func [face] [
        show-old [face]
        hwnd: get-tb-focus
        set-caption hwnd title-text
    ]
]

The following application demonstrates how to use the Windows API to view video from a local web cam, to save snapshots in BMP format, and to change the REBOL GUI window title:

REBOL []

; First, open the Dlls that contain the Windows API functions we want
; to use (to view webcam video, and to change window titles):

avicap32.dll: load/library %avicap32.dll
user32.dll: load/library %user32.dll

; Create REBOL function prototypes required to change window titles:
; (These functions are found in user32.dll, built in to Windows.)

get-focus: make routine! [return: [int]] user32.dll "GetFocus"
set-caption: make routine! [
    hwnd [int] a [string!]  return: [int]
] user32.dll "SetWindowTextA"

; Create REBOL function prototypes required to view the webcam:
; (also built in to Windows)

find-window-by-class: make routine! [
    ClassName [string!] WindowName [integer!] return: [integer!]
] user32.dll "FindWindowA"
sendmessage: make routine! [
    hWnd [integer!] val1 [integer!] val2 [integer!] val3 [integer!]
    return: [integer!]
] user32.dll "SendMessageA"
sendmessage-file: make routine! [
    hWnd [integer!] val1 [integer!] val2 [integer!] val3 [string!]
    return: [integer!]
] user32.dll  "SendMessageA"
cap: make routine! [
    cap [string!] child-val1 [integer!] val2 [integer!] val3 [integer!]
    width [integer!] height [integer!] handle [integer!] 
    val4 [integer!] return: [integer!]
] avicap32.dll "capCreateCaptureWindowA"

; Create the REBOL GUI window:

view/new center-face layout/tight [
    image 320x240
    across
    btn "Take Snapshot" [
        ; Run the dll functions that take a snapshot:
        sendmessage cap-result 1085 0 0
        sendmessage-file cap-result 1049 0 "scrshot.bmp"
    ]
    btn "Exit" [
        ; Run the dll functions that stop the video:
        sendmessage cap-result 1205 0 0
        sendmessage cap-result 1035 0 0
        free user32.dll
        quit
    ]
]

; Run the Dll functions that reset our REBOL GUI window title:
; (eliminates "REBOL - " in the title bar)

hwnd-set-title: get-focus
set-caption hwnd-set-title "Web Camera"

; Run the Dll functions that show the video:

hwnd: find-window-by-class "REBOLWind" 0
cap-result: cap "cap" 1342177280 0 0 320 240 hwnd 0
sendmessage cap-result 1034 0 0
sendmessage cap-result 1077 1 0
sendmessage cap-result 1075 1 0
sendmessage cap-result 1074 1 0
sendmessage cap-result 1076 1 0

; start the GUI:

do-events

For more information about DLLs and the Windows API, see:

http://rebol.com/docs/library.html
http://en.wikipedia.org/wiki/Dynamic_Link_Library
http://www.math.grin.edu/~shirema1/docs/DLLsinREBOL.html
http://www.borland.com/devsupport/borlandcpp/patches/BC52HLP1.ZIP
http://www.allapi.net/downloads/apiguide/agsetup.exe
http://www.activevb.de/rubriken/apiviewer/index-apiviewereng.html
http://msdn.microsoft.com/library/

Remember, whenever you use any Dll or code created by another programmer, be absolutely sure to check, and follow, the licensing terms by which it's distributed.

17.17 A Multiple Network Security Camera App Using The Window's Webcam DLL

This application uses several of the DLL routines from the previous section to demonstrate how to build a security camera monitoring application. This application relies on the common ability of IP cameras to upload a stream of images to an FTP server. This application simply provides an interface to monitor, store, and review frames from up to 24 cameras, to effectively save, browse, search each video stream. Video from a local web cam can be used as a source to test the program.

REBOL [title: "Camera Manager"]
svv/vid-face/color: white
tt: "Camera Manager"
do set-title: {user32.dll: load/library %user32.dll
gf: make routine![return:[int]]user32.dll"GetFocus"
sc: make routine![hw[int]a[string!]return:[int]]user32.dll"SetWindowTextA"
so: :show show: func[face][so[face]hw: gf sc hw tt]}
make-dir %./history/
write %view1cam.r rejoin [{
    REBOL []
    cam: first parse (first system/options/args) "."
    tt: uppercase form cam } set-title {
    blank-image: to-image layout/tight [box black 640x480]
    file: to-file first system/options/args
    gui: view/new center-face layout [
        across
        i1: image (blank-image)
        return
        btn "Stop" [flag: false]
        btn "Start" [flag: true]
        box 0x0 []
    ]
    flag: true
    forever [
        wait .15  if not viewed? gui [quit]  show gui  if flag = true [
            attempt [i1/image: (load file) show i1]
        ]
    ]    
}]
write %viewhist.r rejoin [{
    REBOL []
    svv/vid-face/color: 230.230.230
    change-dir %./history/
    cam: to-file first system/options/args
    tt: uppercase form cam } set-title {
    files: read %./
    if cam <> %all [
        remove-each file files [
            cam-in-file: to-file (first parse (last parse file "_") ".")
            cam <> cam-in-file
        ]
    ]
    last-file: length? files
    counter: 0
    blank-image: to-image layout/tight [box black 640x480]
    update-screen: does [
        attempt [
            i1/image: (load cf: pick files counter)  show i1
            t1/text: rejoin [
                "Current file:  " form cf {  (} counter {/} last-file {)}
            ]
            show t1
        ]
    ]
    gui: view center-face layout [
        across
        i1: image (blank-image)
        return
        btn "Reverse" feel [engage: func [f a e] [
            if find [down over away] a [
                counter: counter - 1
                if counter < 1 [counter: 1]
                update-screen
            ]
        ]]
        btn "Forward" feel [engage: func [f a e] [
            if find [down over away] a [
                counter: counter + 1
                if counter > last-file [counter: last-file]
                update-screen
            ]
        ]]
        btn "Select" [
            selected-file: to-file request-list "Select An Image:" files
            if selected-file = %none [return]
            counter: index? find files selected-file
            update-screen
        ]
        btn "Save" [
            save/png request-file/only/save/file (pick files counter)
                i1/image
        ]
        t1: text bold 370 {
            Select image, or scroll forward/back (arrow keys work)
        }
        key keycode [left] [
            counter: counter - 1
            if counter < 1 [counter: 1]
            update-screen
        ]
        key keycode [right] [
            counter: counter + 1
            if counter > last-file [counter: last-file]
            update-screen
        ]
        key keycode [up] [
            counter: counter - 20
            if counter < 1 [counter: 1]
            update-screen
        ]
        key keycode [down] [
            counter: counter + 20
            if counter > last-file [counter: last-file]
            update-screen
        ]
    ]
}]
write %localcam.r {
    REBOL [title: "Local Camera Test Streamer"]
    avicap32.dll: load/library %avicap32.dll
    user32.dll: load/library %user32.dll
    find-window-by-class: make routine! [
        ClassName [string!] WindowName [integer!] return: [integer!]
    ] user32.dll "FindWindowA"
    sendmessage: make routine! [
        hWnd [integer!] val1 [integer!] val2 [integer!] val3 [integer!]
        return: [integer!]
    ] user32.dll "SendMessageA"
    sendmessage-file: make routine! [
        hWnd [integer!] val1 [integer!] val2 [integer!] val3 [string!]
        return: [integer!]
    ] user32.dll  "SendMessageA"
    cap: make routine! [
        cap [string!] child-val1 [integer!] val2 [integer!] 
        val3 [integer!] width [integer!] height [integer!]
        handle [integer!] val4 [integer!] return: [integer!]
    ] avicap32.dll "capCreateCaptureWindowA"
    gui: view/new center-face layout/tight [
        at -10x-10 b1: box 0x0 
        pic1: image 320x240
    ]
    hwnd: find-window-by-class "REBOLWind" 0
    cap-result: cap "cap" 1342177280 0 0 320 240 hwnd 0
    sendmessage cap-result 1034 0 0
    sendmessage cap-result 1077 1 0
    sendmessage cap-result 1075 1 0
    sendmessage cap-result 1074 1 0
    sendmessage cap-result 1076 1 0
    counter: 1  flag: true
    forever [
        wait .05
        if not viewed? gui [
            sendmessage cap-result 1205 0 0
            sendmessage cap-result 1035 0 0
            free user32.dll
            quit
        ]  
        show b1
        if flag = true [
            sendmessage cap-result 1085 0 0
            filename: rejoin ["cam" counter ".png"]
            sendmessage-file cap-result 1049 0 filename
            counter: counter + 1
            if counter > 24 [counter: 1]
        ]
    ]
}
blank-image: to-image layout/tight [box black 160x120]
gui: view/new center-face layout/tight [
    across
    btn "Stop" [flag: false]
    btn "Start" [flag: true]
    btn "Test With Local Camera" [launch %localcam.r]
    text "View History: "
    drop-down data [
        "cam1" "cam2" "cam3" "cam4" "cam5" "cam6" "cam7" "cam8" "cam9"
        "cam10" "cam11" "cam12" "cam13" "cam14" "cam15" "cam16" "cam17"
        "cam18" "cam19" "cam20" "cam21" "cam22" "cam23" "cam24" "all"
    ] [call/show join "rebol -s %viewhist.r " value]
    t1: text blue "Updating Camera: 000"
    return
    i1: image (blank-image) [call/show "rebol -s %view1cam.r cam1.png"]
    i2: image (blank-image) [call/show "rebol -s %view1cam.r cam2.png"]
    i3: image (blank-image) [call/show "rebol -s %view1cam.r cam3.png"]
    i4: image (blank-image) [call/show "rebol -s %view1cam.r cam4.png"]
    i5: image (blank-image) [call/show "rebol -s %view1cam.r cam5.png"]
    i6: image (blank-image) [call/show "rebol -s %view1cam.r cam6.png"]
    return
    i7: image (blank-image) [call/show "rebol -s %view1cam.r cam7.png"]
    i8: image (blank-image) [call/show "rebol -s %view1cam.r cam8.png"]
    i9: image (blank-image) [call/show "rebol -s %view1cam.r cam9.png"]
    i10: image (blank-image) [call/show "rebol -s %view1cam.r cam10.png"]
    i11: image (blank-image) [call/show "rebol -s %view1cam.r cam11.png"]
    i12: image (blank-image) [call/show "rebol -s %view1cam.r cam12.png"]
    return
    i13: image (blank-image) [call/show "rebol -s %view1cam.r cam13.png"]
    i14: image (blank-image) [call/show "rebol -s %view1cam.r cam14.png"]
    i15: image (blank-image) [call/show "rebol -s %view1cam.r cam15.png"]
    i16: image (blank-image) [call/show "rebol -s %view1cam.r cam16.png"]
    i17: image (blank-image) [call/show "rebol -s %view1cam.r cam17.png"]
    i18: image (blank-image) [call/show "rebol -s %view1cam.r cam18.png"]
    return
    i19: image (blank-image) [call/show "rebol -s %view1cam.r cam19.png"]
    i20: image (blank-image) [call/show "rebol -s %view1cam.r cam20.png"]
    i21: image (blank-image) [call/show "rebol -s %view1cam.r cam21.png"]
    i22: image (blank-image) [call/show "rebol -s %view1cam.r cam22.png"]
    i23: image (blank-image) [call/show "rebol -s %view1cam.r cam23.png"]
    i24: image (blank-image) [call/show "rebol -s %view1cam.r cam24.png"]
]
previous-files: read %./
remove-each file previous-files [%.png = suffix? file]
flag: true
forever [
    wait .05  show i1  if flag = true [
        current-files: read %./
        new-files: exclude current-files previous-files
        foreach file new-files [
            if not viewed? gui [quit]  show i1  if flag = true [
                do process-image: [
                    loaded-file: load file
                    if error? try [
                        rename file to-file rejoin [
                            %./history/ 
                            now/year "-" now/month "-" now/day 
                            "_" replace/all form now/time ":" "-"
                            "_" file
                        ]
                    ] [
                        ; print "error deleting"
                        do process-image
                    ]
                ]
                camnum: replace replace form copy file "cam" "" ".png" ""
                t1/text: join "Updating Camera: " camnum  show t1
                do rejoin [
                    "i" camnum "/image: " loaded-file " show i" camnum
                ]
                wait .05
            ]
        ]
    ]
]

17.18 REBOL as a Browser Plugin

REBOL interpreters exist not only for an enormous variety of operating systems, but also as plugins for several popular browsers (Internet Explorer and many Mozilla variations, including Opera). That means that you can embed the REBOL interpreter directly into a web page, and have complete, complex REBOL programs run right inside pages of your web site (in a way similar to Flash and Java, and useful like Javascript code). This provides a nice alternative to CGI programming for any type of application that runs appropriately in the stand-alone view.exe interpreter (i.e., for games, multimedia applications, and rich graphic/GUI applications of all types). Since the browser plugin runs typical REBOL code in the same way as the downloadable view.exe interpreter, you can run code directly on your web pages, without making any changes.

To use the plugin on a web page, just include the necessary object code on your page, as in the following example. Be sure to change the URL of the script you want to run, the size of the window you want to create, and other parameters as needed. You can download the rebolb7.cab file, upload it to your own site, and run it from there, if you prefer (be aware that there are several different versions: "http://www.rebol.com/plugin/rebolb5.cab#Version=0,5,0,0", "http://www.rebol.com/plugin/rebolb6.cab#Version=0,6,0,0", and "http://www.rebol.com/plugin/rebolb7.cab#Version=1,0,0,0" - use version 7 unless you have a specific reason not to). If you use your own copy, be sure to change the URL of the cab file in the following example:

<HTML><HEAD><TITLE>REBOL Plugin Test</TITLE></HEAD><BODY><CENTER>

<OBJECT ID="REBOL" CLASSID="CLSID:9DDFB297-9ED8-421d-B2AC-372A0F36E6C5" 
    CODEBASE="http://www.rebol.com/plugin/rebolb7.cab#Version=1,0,0,0"
    WIDTH="500" HEIGHT="400">
    <PARAM NAME="LaunchURL" VALUE="http://yoursite.com/test_plugin.r">
    <PARAM NAME="BgColor" VALUE="#FFFFFF">
    <PARAM NAME="Version" VALUE="#FFFFFF">
    <PARAM NAME="BgColor" VALUE="#FFFFFF">
</OBJECT>

</CENTER></BODY></HTML>

Here's an example script that could be run at the "http://yoursite.com/test_plugin.r" link referenced in the code above. You can replace this with any valid REBOL code, and have it run directly in your browser:

REBOL []
view layout [
    size 500x400 
    btn "Click me" [alert "Plugin is working!"]
]

You can see the above example running at http://re-bol.com/test_plugin.html. The above script must be run in Internet Explorer on MS Windows. In order to use the plugin in Mozilla based browsers (Firefox, Opera, etc.), the following code must be pasted into your HTML page:

<HTML><HEAD><TITLE>REBOL Plugin Test</TITLE></HEAD><BODY><CENTER>

<OBJECT ID="REBOL_IE" CLASSID="CLSID:9DDFB297-9ED8-421d-B2AC-372A0F36E6C5"
    CODEBASE="http://re-bol.com/rebolb7.cab#Version=1,0,0,0"
    WIDTH="500" HEIGHT="400" BORDER="1" ALT="REBOL/Plugin">
    <PARAM NAME="bgcolor" value="#ffffff">
    <PARAM NAME="version" value="1.2.0">
    <PARAM NAME="LaunchURL" value="http://re-bol.com/test_plugin.r">
    <embed name="REBOL_Moz" type="application/x-rebol-plugin-v1"
        WIDTH="500" HEIGHT="400" BORDER="1" ALT="REBOL/Plugin"
        bgcolor="#ffffff"
        version="1.2.0"
        LaunchURL="http://re-bol.com/test_plugin.r"
    >
    </embed>
</OBJECT>

<script language="javascript" type="text/javascript">
var plugin_name = "REBOL/Plugin for Mozilla";
function install_rebol_plugin_mozilla() {
    if (navigator.userAgent.toLowerCase().indexOf("msie") == -1) {
        if (InstallTrigger) {
           xpi={'REBOL/Plugin for Mozilla':'http://re-bol.com/mozb2.xpi'};
           InstallTrigger.install(xpi, installation_complete);
        }
    }
}
function installation_complete(url, status) {
    if (status == 0) location.reload();
}
function is_mozilla_plugin_installed() {
    if (window.navigator.plugins) {
        for (var i = 0; i < window.navigator.plugins.length; i++) {
            if (window.navigator.plugins[i].name == plugin_name)
            return true;
        }
    }
    return false;
}
if (!is_mozilla_plugin_installed()) install_rebol_plugin_mozilla();
</script>

</CENTER></BODY></HTML>

You can see the above script working at http://re-bol.com/test_plugin_mozilla.html.

For more information about the REBOL plugins, see http://www.rebol.com/plugin/install.html and http://home.comcast.net/~rebolore/plugin-guide.pdf.

17.19 Using Databases

Databases manage all the difficult details of searching, sorting, and otherwise manipulating large amounts of data, quickly and safely in a multiuser environment. MySQL is a free, open source database system used in many web sites and software projects. ODBC is a common interface that allows programmers to connect to many other types of databases. The most recent releases of REBOL, along with all commercial versions, have built-in native access to MySQL, ODBC, and other database formats. You can also download a free MySQL protocol module that runs in every free version of REBOL, from http://softinnov.org/rebol/mysql.shtml. A free module for the postgre database system is also available at that site.

To explore database concepts and techniques in this section, we'll use the open source MySQL module above because it provides access to a powerful and popular database solution which works even in old and unusual versions of REBOL.

Most web hosting accounts come with MySQL already installed. See your web host account instructions to learn how to access it (you need a web address, database name, user name, and password). To get a free, simple-to-install web server package for Windows that includes MySQL, go to http://www.uniformserver.com. That program enables you to easily install a web server with MySQL pre-configured on your local computer. It's useful if you don't have access to a web server on the Internet, or if you want to create multiuser applications which use MySQL on a local network.

To use the REBOL MySQL module above, unpack the compressed "rip" file available at the link above. This step only needs to be done the first time you use the package on a given computer:

do mysql-107.rip

Every time you access a MySQL database, you need to "do" the module that was unpacked in the step above:

do %mysql-r107/mysql-protocol.r

; At the time of this writing, 1.07 was the most current version of
; the mysql module.  Update the numbers in the previous two lines
; of code to reflect the current version number you've downloaded.

Next, enter the database info (location, username, and password), as in the instructions at http://softinnov.org/rebol/mysql-usage.html:

db: open mysql://username:password@yourwebsite.com/yourdatabasename

In MySQL and other databases, data is stored in "tables". Tables are made up of columns of related information. A "Contacts" table, for example, may contain name, address, phone, and birthday columns. Each entry in the database can be thought of as a row containing info in each of those column fields:

name             address                 phone       birthday
----             -------                 --------    --------
John Smith       123 Toleen Lane         555-1234    1972-02-01
Paul Thompson    234 Georgetown Place    555-2345    1972-02-01
Jim Persee       345 Portman Pike        555-3456    1929-07-02
George Jones     456 Topforge Court                  1989-12-23
Tim Paulson                              555-5678    2001-05-16

"SQL" statements let you work with data stored in the table. Some SQL statements are used to create, destroy, and fill columns with data:

CREATE TABLE table_name          ; create a new table of information
DROP TABLE table_name            ; delete a table
INSERT INTO table_name VALUES (value1, value2,....)
INSERT INTO Contacts 
    VALUES ('Billy Powell', '5 Binlow Dr.', '555-6789', '1968-04-19')
INSERT INTO Contacts (name, phone) 
    VALUES ('Robert Ingram', '555-7890')

The SELECT statement is used to retrieve information from columns in a given table:

SELECT column_name(s) FROM table_name
SELECT * FROM Contacts
SELECT name,address FROM Contacts
SELECT DISTINCT birthday FROM Contacts ; returns no duplicate entries
; To perform searches, use WHERE.  Enclose search text in single
; quotes and use the following operators:
;  =, <>, >, <, >=, <=, BETWEEN, LIKE (use "%" for wildcards)
SELECT * FROM Contacts WHERE name='John Smith'
SELECT * FROM Contacts WHERE name LIKE 'J%'
SELECT * FROM Contacts WHERE birthday LIKE '%72%' OR phone LIKE '%34'
SELECT * FROM Contacts
    WHERE birthday NOT BETWEEN '1900-01-01' AND '2010-01-01'
; IN lets you specify a list of data to match within a column:
SELECT * FROM Contacts WHERE phone IN ('555-1234','555-2345')
SELECT * FROM Contacts ORDER BY name  ; sort results alphabetically
SELECT name, birthday FROM Contacts ORDER BY birthday, name DESC

Other SQL statements:

UPDATE Contacts SET address = '643 Pine Valley Rd.' 
    WHERE name = 'Robert Ingram'     ; alter or add to existing data
DELETE FROM Contacts WHERE name = 'John Smith'
DELETE * FROM Contacts
ALTER TABLE  - change the column structure of a table
CREATE INDEX - create a search key
DROP INDEX   - delete a search key

To integrate SQL statements in your REBOL code, enclose them as follows:

insert db {SQL command}

To retrieve the result set created by an inserted command, use:

copy db

You can use the data results of any query just as you would any other data contained in REBOL blocks. To retrieve only the first result of any command, for example, use:

first db

When you're done using the database, close the connection:

close db

Here's a complete example that opens a database connection, creates a new "Contacts" table, inserts data into the table, makes some changes to the table, and then retrieves and prints all the contents of the table, and closes the connection:

REBOL []

do %mysql-protocol.r 
db: open mysql://root:root@localhost/Contacts
; insert db {drop table Contacts} ; erase the old table if it exists
insert db {create table Contacts (
    name            varchar(100),
    address         text,
    phone           varchar(12),
    birthday        date 
)} 
insert db {INSERT into Contacts VALUES 
    ('John Doe', '1 Street Lane', '555-9876', '1967-10-10'),
    ('John Smith', '123 Toleen Lane', '555-1234', '1972-02-01'),
    ('Paul Thompson', '234 Georgetown Pl.', '555-2345', '1972-02-01'),
    ('Jim Persee', '345 Portman Pike', '555-3456', '1929-07-02'),
    ('George Jones', '456 Topforge Court', '', '1989-12-23'),
    ('Tim Paulson', '', '555-5678', '2001-05-16')
}
insert db "DELETE from Contacts WHERE birthday = '1967-10-10'"
insert db "SELECT * from Contacts"
results: copy db
probe results
close db
halt

Here's a shorter coding format that can be used to work with database tables quickly and easily:

read join mysql://user:pass@host/DB? "SELECT * from DB"

For example:

foreach row read rejoin [mysql://root:root@localhost/Contacts? 
    "SELECT * from Contacts"] [print row]

Here's a GUI example:

results: read rejoin [
    mysql://root:root@localhost/Contacts? "SELECT * from Contacts"]
view layout [
    text-list 100x400 data results [
        string: rejoin [
            "NAME:      " value/1 newline
            "ADDRESS:   " value/2 newline
            "PHONE:     " value/3 newline
            "BIRTHDAY:  " value/4
        ]
        view/new layout [
            area string
        ] 
    ] 
]

For a more detailed explanation about how to set up MYSQL, how to us the SQL language syntax, and other related topics, see http://musiclessonz.com/rebol_tutorial.html#section-27.

17.19.1 SQLite

Here's an example that demonstrates how to use the popular SQLite DBMS, using sqlite.r by Ashley Trutter:

REBOL [title: "SQLITE Example"]
unless exists? %sqlite3.dll [
    write/binary %sqlite3.dll read/binary http://re-bol.com/sqlite3.dll
]
unless exists? %sqlite.r [
    write %sqlite.r read http://re-bol.com/sqlite.r
]
do %sqlite.r
db: connect/create %contacts.db
SQL "create table contacts (name, address, phone, birthday)"
SQL {insert into contacts values 
    ('"John Doe"', '"1 Street Lane"', '"555-9876"', '"1967-10-10"')
}
data: [
    "John Smith" "123 Toleen Lane" "555-1234" "1972-02-01"
    "Paul Thompson" "234 Georgetown Pl." "555-2345" "1972-02-01"
    "Jim Persee" "345 Portman Pike" "555-3456" "1929-07-02"
    "George Jones" "456 Topforge Court" "" "1989-12-23"
    "Tim Paulson" "" "555-5678" "2001-05-16"
]
SQL "begin"
foreach [name address phone bd] data [
    SQL reduce [
        "insert into contacts values (?, ?, ?, ?)" name address phone bd
    ]
]
SQL "commit"
SQL ["DELETE from Contacts WHERE birthday = ?" "1967-10-10"]
results: SQL "select * from contacts"
probe results
disconnect db
halt

To use SQLite in REBOL, see http://www.dobeash.com/sqlite.html.

17.19.2 Other DBMSs

To use ODBC in REBOL, see http://www.rebol.com/docs/database.html.

For a useful open source SQL database system created entirely in native REBOL, see http://www.dobeash.com/rebdb.html.

The following additional database management systems ("DBMS"s) are also available for REBOL:

http://www.tretbase.com/forum/index.php
http://www.fys.ku.dk/~niclasen/nicomdb/
http://www.rebol.net/cookbook/recipes/0012.html
http://www.cs.unm.edu/~whip/
http://www.garret.ru/dybase.html
http://www.rebol.org/view-script.r?script=sql-protocol.r
http://www.rebol.org/view-script.r?script=db.r http://www.rebol.org/view-script.r?script=couchdb3.r

Be sure to search rebol.org for more information and code related to databases.

17.20 Menus

One oddity about Rebol's GUI dialect is that it doesn't incorporate a native way to create standard menus. Users typically click buttons or text choices directly in REBOL GUIs to make selections. The "request-list" function and the GUI "choice" widget are short and simple substitutes which provide menu-like functionality.

The example below demonstrates how to stylize the choice widget to create normal looking menus. Use "editor decompress #{compressed code}" to examine how it works. Otherwise, just follow the menu format in the example, fill in your own GUI code, and paste the compressed chunk into your own script:

REBOL [title: "Choice Button Menu Example"]
menu: [[
    "File" []
    "_________________________^/" []
    "File Option 1" [alert "File Option 1"]
    "File Option 2" [alert "File Option 2"]
    "File Option 3" [alert "File Option 3"]
    "_________________________^/" []
    "About" [do-face b1 1]
][
    "Edit" []
    "_________________________^/" []
    "Edit Option 1" [alert "Edit Option 1"]
    "Edit Option 2" [alert "Edit Option 2"]
    "Edit Option 3" [alert "Edit Option 3"]
][
    "Preferences" []
    "_________________________^/" []
    "Preferences Option 1" [alert "Preferences Option 1"]
    "Preferences Option 2" [alert "Preferences Option 2"]
    "_________________________^/" []
    "Preferences Option 3" [alert "Preferences Option 3"]
]]
gui: [
    a1: area wrap with [colors: [254.254.254 248.248.248]]
    b1: btn "About" [alert "These menus are just a choice button widgets"]
]
do decompress #{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}
view center-face layout gui

The example below demonstrates a useful menu widget by Cyphre (shown earlier in the presentation section of this tutorial), which makes it easy to add nice looking menus to your GUIs. This example also includes Cyphre's Tab Panel widget, which is a great way to maximize screen real estate in programs with large GUIs. The code demonstrated here is the author's preferred way to add menus to REBOL programs:

REBOL [title: "Cyphre's Menu and Tab Panel Example"]

; Menu Widget:

do load decompress #{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}

; Tab Panel Widget: 

do load decompress #{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D1BB50C4D45CE2554CABB36AED18F94E614D8C15A87813FC7A43452753A4D130
FEFE1F50628086731B0000
}

insert-event-func [ 
    either event/type = 'resize [
        mn/size/1: system/view/screen-face/pane/1/size/1 
        my-tabs/size: system/view/screen-face/pane/1/size - 15x30
        show [mn my-tabs]  none
    ] [event]
]

view/options center-face layout  [
    across space 0x0 origin 0x0
    mn: menu with [ 
        size: 470x20 
        data: compose/deep [
            " File " [
                "Open" # "Ctrl+O" [request-file]
                "Save" # "Ctrl+S" [request-file/save]
                bar
                "Exit" [quit]
            ]
            " Options " [
                "Preferences" sub [
                    "Colors" [alert form request-color]
                    "Settings" [request-text/title "Enter new setting:"]
                ]
                "About" [alert "Menu Widget by Cyphre"]
            ]
        ]
    ]
    below
    at 10x25 my-tabs: tab-panel data [
        "Fields"   [
            h1 "Tab Panel by Cyphre" field field area area btn "Ok"
         ]
        "Data List"  [
            t1: text-list 400x430 data system/locale/months [alert value]
        ]
    ]
] [resize]

For full blown menus with all the bells and whistles, animated icons, appropriate look-and-feel for various operating systems, and every possible display option, a module has been created to easily provide that capability: http://www.rebol.org/library/scripts/menu-system.r. Here's a minimal example demonstrating it's use:

do-thru http://www.rebol.org/library/scripts/menu-system.r
menu-data: [edit: item "Menu" menu [item "Item1" item "Item2"]]
simple-style: [item style action [alert item/body/text]]

view center-face layout/size [
    at 2x2 menu-bar menu menu-data menu-style simple-style
] 400x500

Here's a typical example that demonstrates the basic syntax for common menu layouts:

REBOL []

; You can download the menu-system.r script to your hard drive:

if not exists? %menu-system.r [write %menu-system.r (
        read http://www.rebol.org/library/scripts/menu-system.r)]

; If you're packaging your program into an .exe file, be sure to
; include the menu-system.r script in your package:

do %menu-system.r

; Here's how to create a menu layout:
; The "menu-data" block contains all the top level menus.
; Items in each of those menus go into separate "menu" blocks.
; Submenus are simply items with their own additional "menu" blocks.
; Use "---" for separator lines:

menu-data: [
    file: item "File" menu [item "Open" item "Save" item "Quit"]
    edit: item "Edit" menu [ 
        item "Item 1"
        item "Item 2" <ctrl-q>
        ---
        item "Submenu..." menu [
            item "Submenu Item 1" 
            item "Submenu Item 2"
            item "Submenu Item 3" menu [
                item "Sub-Submenu Item 1"
                item "Sub-Submenu Item 2"
            ]
        ]
        ---
        item "Item 3"       
    ]
    icons: item "Icons" menu [
        item "Icon Item 1" icons [help.gif stop.gif]
        item "Icon Item 2" icons [info.gif exclamation.gif]
    ]
]

; Each menu selection can now run any code you want.
; Just use the "switch" structure below:

basic-style: [item style action [
    switch item/body/text [
        ; put any code you want, in each block:
        case "Open" [
            the-file: request-file
            alert rejoin ["You opened: " the-file]
        ] 
        case "Save" [
            the-file: request-file/save
            alert rejoin ["You saved to: " the-file]
        ]
        case "Quit" [
            if (request/confirm "Really Quit?") = true [quit]
        ]   
        case "Item 1" [alert "Item 1 selected"]
        case "Item 2" [alert "Item 2 selected"]
        case "Item 3" [alert "Item 3 selected"]
        case "Submenu Item 1" [alert "Submenu Item 1 selected"]
        case "Submenu Item 2" [alert "Submenu Item 2 selected"]
        case "Submenu Item 3" [alert "Submenu Item 3 selected"]
        case "Sub-Submenu Item 1" [alert "Sub-Submenu Item 1 selected"]
        case "Sub-Submenu Item 2" [alert "Sub-Submenu Item 2 selected"]
        case "Icon Item 1" [alert "Icon Item 1 selected"]
        case "Icon Item 2" [alert "Icon Item 2 selected"]
    ]
]]

; The following lines need to be added to eliminate a potential problem
; closing down:

evt-close: func [face event] [either event/type = 'close [quit] [event]]
insert-event-func :evt-close

; Now put the menu in your GUI, as follows:

view center-face layout [
    size 400x500
    ; use this stock code:
    at 2x2 menu-bar menu menu-data menu-style basic-style
]

The demo at http://www.rebol.org/library/scripts/menu-system-demo.r shows off many more advanced features of the module.

Below is an intermediate example with explanations of the most important features. It also includes some stock code to display menus with a standard MS Windows style (OS specific appearance). The menu module has been compressed and embedded directly into the script, using "compress read http://www.rebol.org/library/scripts/menu-system.r" (so that the module does not need to be downloaded or included as a separate file):

REBOL [Title: "Menu Example"]

; The following line imports the compressed menu module.  

do decompress #{
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}

; Note that there are two menus in the following 
; block.  The "file" menu is indented and spread 
; across several lines.  The edit menu is all on
; one line.  Notice that you can place action blocks
; after each menu item, to be performed whenever the
; menu item is selected - as with the [print "You
; chose Item 1"] block below:

menu-data: [
    file: item "File" 
        menu [
            new:    item "Item 1" [print "You chose Item 1"]
            open:   item "Item 2" ; icons [1.png 2.png]
            ---
            recent: item "Look In Here..."
                menu [
                    item "WIN A PRIZE!" 
                    item "Try door number two"
                ]
            ---
            exit:   item <Ctrl-Q> "Exit"   
          ]
    edit: item "Edit" menu [item "copy" item "paste"]
] 

; Most of the style definition below is totally optional.
; It's designed to look like a native Microsoft menu.  The
; example at
; http://www.rebol.org/library/scripts/menu-system-demo.r
; contains many more examples of menu styles and options.
; The only part that's required in the example below is 
; the action block in the "item style" section.  Everything
; else serves only to adjust the cosmetic appearance of the
; menu:

winxp-menu: layout-menu/style copy menu-data xp-style: [
    menu style edge [size: 1x1 color: 178.180.191 effect: none]
        color white
        spacing 2x2 
        effect none
    item style 
        font [name: "Tahoma" size: 11 colors: reduce [
            black black silver silver]]
        colors [none 187.183.199] 
        effects none
        edge [size: 1x1 colors: reduce [none 178.180.191] 
            effects: []]    
        action [

            ; Change the lines below to fit your needs.
            ; You can use the action block of each item
            ; in the switch structure to run your own 
            ; functions.  "item/body/text" refers to the
            ; selected menu item.  This does the exact same
            ; thing as including a code block for each item
            ; in the menu definition above (i.e., you can
            ; put the [quit] block after the "exit" item 
            ; above, and it will perform the same way - 
            ; just like the "[print "You chose Item 1"]" 
            ; block after the "new" item above).

            switch/default item/body/text [
                "exit" [quit]
                "WIN A PRIZE!" [alert "You win!"]
                "Try door number two" [alert "Bad choice :("]
            ] [print item/body/text]  ; default thing to do
        ]
]

; The following function traps the GUI close event.  This
; must be included whenever the menu module is used, or a 
; portion of the application will continue to run after being
; shut down. 

evt-close: func [face event] [
    either event/type = 'close [quit] [event]
]
insert-event-func :evt-close

; And finally, here's the user interface:

window: layout [

    size  400x500

    ; The line below shows the winxp style menu:

    at 2x2 app-menu: menu-bar menu menu-data menu-style xp-style

    ; THE LINE BELOW SHOWS THE SAME MENU, WHENEVER THE BUTTON 
    ; IS CLICKED:

    at 150x200 btn "Menu Button" [
        show-menu/offset window winxp-menu
        0x1 * face/size + face/offset - 1x0
    ]
]

view center-face window

The popular REBOL GUI tool called RebGUI (covered in a later section of this tutorial) also has a simple facility for creating basic menus, which can be useful.

17.21 Creating Multi Column GUI Text Lists (Data Grids) From Scratch

REBOL's built-in "text-list" GUI widget is very simple to use, but it can only display one column of data:

view layout [text-list data (system/locale/months)]

REBOL does have a built-in "list" widget for multiple column "data grid" displays, but it's a bit more complex to use than the text-list widget. Earlier in this text, Henrik Mikael Kristensen's listview module was introduced as a simple solution for creating multiple column data grid displays. It works well, but requires you to include a third party module. With a little knowledge and practice, you'll find that REBOL's built-in list widget can be very powerful and easy to use. In it's simplest form, the native list widget takes a size parameter, and 2 additional block parameters:

list (size) [GUI widget layout block] data [block(s) of data to display]

The "(size)" parameter is an XxY pair indicating the pixel size of the overall list widget. The "[GUI widget layout block]" is a layout of standard VID widgets used to display each row of data in the grid. The GUI elements in this block are replicated to display each consecutive row of data in the grid. The GUI layout block typically contains the word "across" (because these widgets are used to display rows of data), and it typically includes size parameters for each widget. The "data" block is made up of rows of information to be displayed in the grid. Each row of data is contained in a separate interior block:

view layout [
    list 220x100 [across text 100 text 100] data [
        ["row 1, column 1" "row 1, column 2"]
        ["row 2, column 1" "row 2, column 2"]
        ["row 3, column 1" "row 3, column 2"]
        ["row 4, column 1" "row 4, column 2"]
    ]
]

The GUI block can contain other standard facet modifiers such as colors and spacing:

view layout [
    list 200x100 [across space 0 text red 100 text blue 100] data [
        ["row 1, column 1" "row 1, column 2"]
        ["row 2, column 1" "row 2, column 2"]
        ["row 3, column 1" "row 3, column 2"]
        ["row 4, column 1" "row 4, column 2"]
    ]
]

The GUI block does not need to be comprised of only text fields. You can display the rows of data on widgets of any type:

view layout [
    list 304x100 [across space 0 button 150 button 150] data [
        ["row 1, column 1" "row 1, column 2"]
        ["row 2, column 1" "row 2, column 2"]
        ["row 3, column 1" "row 3, column 2"]
        ["row 4, column 1" "row 4, column 2"]
    ]
]

IMPORTANT: You can make widgets in the list perform actions, just like in any other "view layout" code:

view layout [
    list 304x100 [
        across space 0 
        button 150 [alert face/text]  ; When clicked, alert the text
        button 150 [alert face/text]  ; contained on the button's face.
    ] data [
        ["row 1, column 1" "row 1, column 2"]
        ["row 2, column 1" "row 2, column 2"]
        ["row 3, column 1" "row 3, column 2"]
        ["row 4, column 1" "row 4, column 2"]
    ]
]

This means that creating user editable cells is very simple - just reassign the text of the clicked face, then update the display:

view layout [
    list 304x92 [
        across space 0 
        btn 150 [face/text: request-text/default face/text show face]
        btn 150 [face/text: request-text/default face/text show face]
    ] data [
        ["row 1, column 1" "row 1, column 2"]
        ["row 2, column 1" "row 2, column 2"]
        ["row 3, column 1" "row 3, column 2"]
        ["row 4, column 1" "row 4, column 2"]
    ]
]

Unintentional visual artifacts can be caused by the caret (cursor) in text widgets. To eliminate them, simply focus and unfocus the widget after updating the display:

view gui: layout [
    list 304x84 [
        across space 0 
        text 150 [
            face/text: request-text/default face/text
            show gui focus face unfocus face
        ]
        text 150 [
            face/text: request-text/default face/text 
            show gui focus face unfocus face
        ]
    ] data [
        ["row 1, column 1" "row 1, column 2"]
        ["row 2, column 1" "row 2, column 2"]
        ["row 3, column 1" "row 3, column 2"]
        ["row 4, column 1" "row 4, column 2"]
    ]
]

Notice that the number of rows contained in the data block does not affect the number of rows displayed. The list always shows as many rows as will fit in the overall pixel size of the widget (we'll attend to this issue later...):

view layout [
    list 304x100 [across space 0 button 150 button 150] data [
        ["row 1, column 1" "row 1, column 2"]
    ]
]

view layout [
    list 304x100 [across space 0 button 150 button 150] data [
        ["row 1, column 1" "row 1, column 2"]
        ["row 2, column 1" "row 2, column 2"]
        ["row 3, column 1" "row 3, column 2"]
        ["row 4, column 1" "row 4, column 2"]
        ["row 5, column 1" "row 5, column 2"]
        ["row 6, column 1" "row 6, column 2"]
        ["row 7, column 1" "row 7, column 2"]
    ]
]

You can resize lists to stretch and fit resizable GUI windows:

insert-event-func [
    either event/type = 'resize [
        li/size: gui/size - 40x40
        t1/size: t2/size: as-pair (round (li/size/1 / 2)) 19
        show li unview view gui
        none
    ][event]
]
view/options gui: layout [
    li: list 220x110 [across t1: text 100 t2: text 100] data [
        ["row 1, column 1" "row 1, column 2"]
        ["row 2, column 1" "row 2, column 2"]
        ["row 3, column 1" "row 3, column 2"]
        ["row 4, column 1" "row 4, column 2"]
    ]
] [resize]

Here's one way to stretch and/or shrink all the cells to fit inside a resizable list:

gui-size: 220x110  li-size: 100x19
gui-block: [
    li: list li-size [
        across 
        text first (li-size / 2)  ; (1/2 the width of the list widget)
        text first (li-size / 2)
    ] data [
        ["row 1, column 1" "row 1, column 2"]
        ["row 2, column 1" "row 2, column 2"]
        ["row 3, column 1" "row 3, column 2"]
        ["row 4, column 1" "row 4, column 2"]
    ]
]
insert-event-func [
    either event/type = 'resize [
        li-size: gui/size - 40x40
        unview
        view/options gui: layout gui-block [resize]
        none
    ][event]
]
view/options gui: layout gui-block [resize]

Of course, you can assign a label to any properly formatted data block, and display it later in a list widget:

x: [
    ["row 1, column 1" "row 1, column 2"]
    ["row 2, column 1" "row 2, column 2"]
    ["row 3, column 1" "row 3, column 2"]
    ["row 4, column 1" "row 4, column 2"]
]

view layout [list 220x100 [across text 100 text 100] data x]

That allows you to build and display multi-column lists very easily:

x: copy []
for i 1 12 1 [
    some-info: copy []
    append some-info (pick system/locale/months i)
    append some-info (pick system/locale/days i)
    append/only x some-info
]

view layout [list 220x240 [across text 100 text 100] data x]

Here's a resizable version of the script above, which has user editing enabled for the first column only:

x: copy []
for i 1 12 1 [
    some-info: copy []
    append some-info (pick system/locale/months i)
    append some-info (pick system/locale/days i)
    append/only x some-info
]
gui-size: 220x110  li-size: 100x19
gui-block: [
    li: list li-size [
        across 
        text first (li-size / 2) [
            face/text: request-text/default face/text  ; enable user edit
            show face focus face unfocus face
        ]
        text first (li-size / 2) 
    ] data x
]
insert-event-func [
    either event/type = 'resize [
        li-size: gui/size - 40x40
        unview
        view/options gui: layout gui-block [resize]
        none
    ][event]
]
view/options gui: layout gui-block [resize]

You can collect the entire block of user-edited data using the following code:

editor second second get in (list-widget-label) 'subfunc

For example:

view layout [
    the-list: list 304x100 [
        across space 0 
        info 150 [face/text: request-text/default face/text show face]
        info 150 [face/text: request-text/default face/text show face]
    ] data [
        ["row 1, column 1" "row 1, column 2"]
        ["row 2, column 1" "row 2, column 2"]
        ["row 3, column 1" "row 3, column 2"]
        ["row 4, column 1" "row 4, column 2"]
    ]
    btn "Display Current Data" [
        editor second second get in the-list 'subfunc
    ]
]

This can be used to save and load all data in the list to files, or otherwise put to use. That makes the widget very useful for data management of all types! Take a look at this script to see one way to save and load data:

x: copy [
    ["row 1, column 1" "row 1, column 2"]
    ["row 2, column 1" "row 2, column 2"]
    ["row 3, column 1" "row 3, column 2"]
    ["row 4, column 1" "row 4, column 2"]
]
do qq: [view layout [
    the-list: list 304x100 [
        across space 0 
        info 150 [face/text: request-text/default face/text show face]
        info 150 [face/text: request-text/default face/text show face]
    ] data x
    across
    btn "Save" [
        save to-file request-file/save
            second second get in the-list 'subfunc
        show the-list
    ]
    btn "Load" [
        x: copy load to-file request-file
        unview do qq
    ]
]]

17.21.1 The "Supply" Function

To enable more versatile list displays, the "data" block can be replaced with a "supply" function. "Supply" works much like a "for" loop that iterates through each row of widgets in the displayed GUI list. The "supply" function automatically creates 2 new variables which are automatically incremented each time through the rows in the list:

  1. "count": the current ROW in the list
  2. "index": the current COLUMN in the current row

You can use the "count" and "index" variables to select sequential values from a block of data, using the "pick" function (in the same way as in a for loop). Typically, this is used to set the "/text" property of each widget in every row.

In the following example, every row in the list contains a single text widget. The supply function runs through each row, and sets the text property of the widget's face to be one item from the "x" block (a list of months). The loop automatically increments the "count" variable to display each of the months:

x: copy system/locale/months

view layout [ 
    list 200x300 [text 200] supply [
        face/text: pick x count
    ]
]

This example loops through a list of files read from the current directory:

x: read %.

view layout [
    list 200x400 [text 200] supply [face/text: pick x count]
]

You can use the "count" variable to change properties of each widget face. In this example, the color property of alternate rows is changed (one color is assigned to even counted rows, another to odd rows):

x: read %.

view layout [
    list 200x400 [text 200] supply [
       either even? count [face/color: white][face/color: tan]
       face/text: pick x count
    ]
]

You can apply actions to any widget in a list, just as you can with any other widget. Clicking on any file name in the list below will open that file in the editor:

x: read %.

view layout [
    list 200x400 [
        text 200 [editor to-file face/text]
    ] supply [
        face/text: pick x count
    ]
]

You can use the "count" variable in the supply function to build multi-column lists from 2 or more separate data blocks (multi column grids are the whole point of learning to use the list widget):

x: copy system/locale/months
y: copy system/locale/days

view layout [
    list 250x400 [across t1: text 50 t2: text 100 t3: text 100] supply [
        t1/text: count
        t2/text: pick x count
        t3/text: pick y count
    ]
]

The next example uses both the "count" and "index" variables to loop through a block with 2 columns of data. Understanding this format is the basis for all the most complex list layouts you'll need. Take special notice of the first line in the supply block. Once all the data from the "x" block has been looped through, if there are more rows in the list display, the index value will go past the length of the data block, and cause an error. To avoid this, you simply check if the picked value is "none", and apply a value of none to the face/text, then exit the loop:

x: copy []
for i 1 12 1 [
    append/only x reduce [
        pick system/locale/months i
        pick system/locale/days i 
    ]
]

view layout [
    list 400x400 [across text 200 text 200] supply [
        if none? q: pick x count [face/text: none exit]
        face/text: pick q index
    ]
]

To help clarify the above format, here's the same example with a third row added:

x: copy []
for i 1 12 1 [
    append/only x reduce [
        i
        pick system/locale/months i
        pick system/locale/days i 
    ]
]

view layout [
    list 250x300 [
        across 
        text 50 
        text 100
        text 100
    ] supply [
        if none? q: pick x count [face/text: none exit]
        face/text: pick q index
    ]
]

Here's an example of the directory reading example from earlier, but with two columns of data displayed (file name and size). Clicked file names still bring up the editor:

y: read %.
x: copy []
foreach i y [append/only x reduce [i (size? to-file i)]]

view layout [
    list 300x400 [
        across
        text 200 [editor to-file face/text]
        text 100
    ] supply [
        if none? q: pick x count [face/text: none exit]
        face/text: pick q index
    ]
]

The following example demonstrates how to add a slider to scroll through items in a large data block:

x: copy []  for i 1 397 1 [append x i]

slider-pos: 0
view layout [
    across
    the-list: list 240x400 [text 200] supply [
        count: count + slider-pos
        face/text: pick x count
    ]
    slider 16x400 [
        slider-pos: (length? x) * value
        show the-list
    ]
]

Here's the above slider technique applied to the earlier directory reading example:

x: read %.

slider-pos: 0
view layout [
    across
    the-list: list 300x400 [
        text 200 [editor to-file face/text]
    ] supply [
        count: count + slider-pos
        face/text: pick x count
    ]
    slider 16x400 [
        slider-pos: (length? x) * value
        show the-list
    ]
]

Here's the 2 column version of the directory reading script, with a slider attached. Be aware that clicking on any file name still reads and edits that file:

y: read %.
x: copy []
foreach i y [append/only x reduce [i (size? to-file i)]]

slider-pos: 0
view layout [
    across
    the-list: list 300x400 [
        across
        text 200 [editor to-file face/text]
        text 100
    ] supply [
        count: count + slider-pos
        if none? q: pick x count [face/text: none exit]
        face/text: pick q index
    ]
    slider 16x400 [
        slider-pos: (length? x) * value
        show the-list
    ]
]

Here's another refinement of the above script, with a third column added. The look of this display is changed by adding a line between each row (the line is drawn using a box widget), and by changing the color and font of the text:

y: read %.
c: 0
x: copy []
foreach i y [append/only x reduce [(c: c + 1) i (size? to-file i)]]

slider-pos: 0
view layout [
    across space 0
    the-list: list 400x400 [
        across 0 space 0x0
        text 50 purple
        text 250 bold [editor read to-file face/text]
        text 100 red italic
        return box green 400x1
    ] supply [
        count: count + slider-pos
        if none? q: pick x count [face/text: none exit]
        face/text: pick q index
    ]
    slider 16x400 [
        slider-pos: (length? x) * value
        show the-list
    ]
]

This example by Carl Sassenrath demonstrates a basic 4 column display:

REBOL [] 

db: [
    [ "000" "Ian Fleming" "ian" 31-Dec-2003 ]
    [ "007" "James Bond" "jb" 1-Jan-2004 ]
    [ "001" "M" "m" 2-Jan-2004 ]
    [ "ABC" "Miss Moneypenny" "missm" 3-Jan-2004]
    [ "008" "Pierce Brosnan" "pb" 4-Jan-2004 ]
    [ "009" "George Lazenby" "gl" 5-Jan-2004 ]
    [ "010" "Roger Moore" "rm" 6-Jan-2004 ]
]
sld-cnt: 0
view lst1: layout [across space 0x0 
    style text text [alert form face/user-data] 
    list 406x100 [
        across space 0x0 text 36 text 100 text 120 text 150
    ] supply [
        face/text: none face/user-data: none
        count: count + sld-cnt
        record: pick db count
        if not record [exit]
        n: pick [1 2 3 4] index
        face/text: pick record n
        face/user-data: record
    ]
    scl1: scroller 16x100 [
        value: to-integer value * length? db
        if value <> sld-cnt [sld-cnt: value show lst1]
    ]
]

The following example demonstrates how to enable users to add and remove data from a list display. Notice that after adjusting the content of your original data block and then "show"ing the list, the displayed grid is automatically updated with the new data:

x: copy []
for i 1 10 1 [
    append/only x reduce [form random 1000 form random 1000]
]

slider-pos: 0
view layout [
    across
    the-list: list 220x240 [across text 100 text 100] supply [
        count: count + slider-pos
        if none? q: pick x count [face/text: none exit]
        face/text: pick q index
    ]
    slider 16x240 [
        slider-pos: (length? x) * value
        show the-list
    ]
    return
    btn "Remove" [remove head x  show the-list
    ]
    btn "Add" [
        insert/only head x reduce [form random 1000 form random 1000]
        show the-list
    ]
]

To save user-edited contents of a GUI list created with the "supply" function, you need to use the following "set-it" code when iterating through the supply function with "count" and "index" (the "second second get in (list-widget-label) 'subfunc" trick only works for lists created using the "data" function):

x: copy [
    ["row 1, column 1" "row 1, column 2"]
    ["row 2, column 1" "row 2, column 2"]
    ["row 3, column 1" "row 3, column 2"]
    ["row 4, column 1" "row 4, column 2"]
]
do qq: [view gui: layout [
    the-list: list 304x100 [
        across space 0 
        info 150 [face/text: request-text/default face/text show gui]
        info 150 [face/text: request-text/default face/text show gui]
    ] supply [
        either count > length? x [face/text: "" face/image: none] [
            the-list/set-it face x index count
        ]
    ]
    across
    btn "Save" [
        save to-file request-file/save x
    ]
    btn "Load" [
        x: copy load to-file request-file
        unview do qq
    ]
]]

In this example, columns can be sorted by clicking the headers. Individual values at any column/row position can be edited by the user (just click the current value). Entire rows can be added, removed, or moved to/from user-selected positions. The data block can be saved or loaded to/from file(s). Scrolling can be done with the mouse, arrow keys, or page-up/page-down keys. Several resizing concepts are also demonstrated:

REBOL [title: "List Widget Example"]

x: copy []   random/seed now/time   ; generate 5000 rows of random data:
repeat i 5000 [
    append/only x reduce [random "asdfqwertyiop" form random 1000 form i]
]  y: copy x
Alert help-txt: {Be sure to try the following features:  1) Resize the GUI
    window to see the list automatically adjust to fit  2) Click column
    headers to sort by field  3) Use the arrow keys and page-up/page-down
    keys to scroll  4) Use the Insert, Delete and "M" keys to add, remove
    and move rows (by default, at the currently highlighted row)  5) Click
    the small "r" header button in the top right corner to reset the list
    back to its original values  6) Click any individual data cell to edit
    the selected value.}
sort-column: func [field] [
    either sort-order: not sort-order [
        sort/compare x func [a b] [(at a field) > (at b field)]
    ] [
        sort/compare x func [a b] [(at a field) < (at b field)]
    ]  
    show li
]
key-scroll: func [scroll-amount] [
    s-pos: s-pos + scroll-amount
    if s-pos > (length? x) [s-pos: length? x]
    if s-pos < 0 [s-pos: 0]
    sl/data: s-pos / (length? x)  
    show li  show sl
]
resize-grid: func [percentage] [
    gui-size: system/view/screen-face/pane/1/size ; - 10x0
    list-size/1: list-size/1 * percentage
    list-size/2: gui-size/2 - 95
    t-size: round (list-size/1 / 3)
    sl-size: as-pair 16 list-size/2
    unview/only gui view/options center-face layout gui-block [resize]
]
resize-fit: does [
    gui-size: system/view/screen-face/pane/1/size
    resize-grid (gui-size/1 / list-size/1 - .1)
]
insert-event-func [either event/type = 'resize [resize-fit none] [event]]
gui-size: system/view/screen-face/size - 0x50
list-size: gui-size - 60x95
sl-size: as-pair 16 list-size/2
t-size: round (list-size/1 / 3)
s-pos: 0  sort-order: true  ovr-cnt: none  svv/vid-face/color: white
view/options center-face gui: layout gui-block: [
    size gui-size  across
    btn "Smaller" [resize-grid .75]
    btn "Bigger" [resize-grid 1.3333]
    btn "Fit" [resize-fit]
    btn #"^~" "Remove" [attempt [
        indx: to-integer request-text/title/default "Row to remove:" 
            form to-integer ovr-cnt
        if indx = 0 [return]
        if true <> request rejoin ["Remove: " pick x indx "?"] [return]
        remove (at x indx)  show li
    ]]
    insert-btn: btn "Add" [attempt [
        indx: to-integer request-text/title/default "Add values at row #:"
            form to-integer ovr-cnt
        if indx = 0 [return]
        new-values: reduce [
            request-text request-text (form ((length? x) + 1))
        ]
        insert/only (at x indx) new-values  show li
    ]]
    btn #"m" "Move" [
        old-indx: to-integer request-text/title/default "Move from row #:"
            form to-integer ovr-cnt
        new-indx: to-integer request-text/title "Move to row #:"
        if ((new-indx = 0) or (old-indx = 0)) [return]
        if true <> request rejoin ["Move: " pick x old-indx "?"] [return]
        move/to (at x old-indx) new-indx  show li
    ]
    btn "Save" [save to-file request-file/save x]
    btn "Load" [y: copy x: copy load request-file/only  show li]
    btn "Read Me" [alert help-txt]
    btn "View Data" [editor x]
    return  space 0x0
    style header button as-pair t-size 20 black white bold
    header "Random Text" [sort-column 1]
    header "Random Number" [sort-column 2] 
    header "Unique Key" [sort-column 3]
    button black "r" 17x20 [if true = request "Reset?"[x: copy y show li]]
    return
    li: list list-size [
        style cell text t-size feel [
            over: func [f o] [
                if (o and (ovr-cnt <> f/data)) [ovr-cnt: f/data show li]
            ]
            engage: func [f a e] [
                if a = 'up [
                    f/text: request-text/default f/text show li
                ]
            ]
        ]             
        across  space 0x0
        col1: cell blue
        col2: cell
        col3: cell red
    ] supply [
        either even? count [face/color: white] [face/color: 240.240.255]
        count: count + s-pos
        if none? q: pick x count [face/text: copy "" exit]
        if ovr-cnt = count [face/color: 200.200.255]
        face/data: count
        face/text: pick q index
    ]
    sl: scroller sl-size [s-pos: (length? x) * value  show li]
    key keycode [up] [key-scroll -1]
    key keycode [down] [key-scroll 1]
    key keycode [page-up] [key-scroll -20]
    key keycode [page-down] [key-scroll 20]
    key keycode [insert] [do-face insert-btn 1]
] [resize]

Be sure to see http://www.rebol.org/view-script.r?script=list-supply-how-to.r, http://www.rebol.org/view-script.r?script=vid-usage.r, http://www.rebol.org/view-script.r?script=list-scroll-demo.r, and http://www.pat665.free.fr/gtk/rebol-view.html#sect19. for more about lists.

17.21.2 Creating Home Made Multi Column Data Grids

As it turns out, it can actually be easier and more versatile to roll your own data grids using native VID components, than it is to use the "list" widget. The following examples are based on the concept at http://www.rebol.org/view-script.r?script=presenting-text-in-columns.r. In every example, a forskip loop is used to build a visual grid of GUI widgets. The loop inserts individual text items from a data block onto each widget's face. For large lists, these example run slowly, but they can be useful for creating reasonably small displays.

The first example creates a random block of two columns of data, labeled "x". Then, a forskip loop is used to assemble a layout block of field widgets, with each row of fields containing 2 consecutive text items from the data block. That GUI block is then displayed on a pane inside a box widget, which is itself displayed inside the layout of the main window. A scroller widget is added to scroll the visible portion of the grid layout. This is accomplished by adjusting the offset of the pane which contains the whole layout of field widgets. IMPORTANT: notice that each cell in this grid is user editable (simply because each cell is displayed using a standard VID field widget). Also notice that the data is converted to a string with the "form" function, because fields can only display text.

x: copy [] for i 1 179 1 [append x reduce [i random "abcd"]]

grid: copy [across space 0]  ; the GUI block containing the grid of fields
forskip x 2 [append grid compose [field (form x/1)field (form x/2)return]]
view center-face layout [across
    g: box 400x200 with [pane: layout/tight grid pane/offset: 0x0]
    scroller [g/pane/offset/y: g/size/y - g/pane/size/y * value show g]
]

The next example demonstrates how to take two columns of data (blocks) and combine them into a single block that can be displayed using the layout above. First, the size of the longest block is determined using the "max" function, and a for loop is run to add consecutive items from each of the source blocks, in groups of 2, to the destination block. If either column runs out of data, blank strings are added to the rest of the destination block as column place holders.

x: copy [] 
block1: copy system/locale/months  block2: copy system/locale/days
for i 1 (max length? block1 length? block2) 1 [
    append x either g: pick block1 i [g] [""]
    append x either g: pick block2 i [g] [""]
]

grid: copy [across space 0]
forskip x 2 [append grid compose [field (form x/1)field (form x/2)return]]
view center-face layout [across
    g: box 400x200 with [pane: layout/tight grid pane/offset: 0x0]
    scroller [g/pane/offset/y: g/size/y - g/pane/size/y * value show g]
]

The next example demonstrates how to change the look of the grid layout, and how to obtain a block containing all the data displayed in the grid, including user edits. To clarify visual separation of row data, an alternating color is assigned to each row in the grid. This is handled using a "remainder" function to check for even numbered rows. For every 4 pieces of text in the data block (every 2 displayed rows), the color is set to white. Otherwise, it's set to wheat. The most important part of this example is the line which collects all the data contained in each face of the displayed grid, and builds a block ("q") to store it.

x: copy [] for i 1 179 1 [append x reduce [i random "abcd"]]

grid: copy [origin 0x0 across space 0x0]
forskip x 2 [
    color: either (remainder ((index? x) - 1) 4) = 0 [white][wheat]
    append grid compose [
        field 180 (form x/1) (color) edge none
        field 180 (form x/2) (color) edge none return
    ]
]
view center-face layout [
    across space 0  
    g: box 360x200 with [pane: layout grid pane/offset: 0x0]
    scroller[g/pane/offset/y: g/size/y - g/pane/size/y * value / 2 show g]
    return box 1x10 return  ; just a spacer
    btn "Get Data Block (INCLUDING USER EDITS)" [
        q: copy [] foreach face g/pane/pane [append q face/text] editor q
    ]
]

The next example demonstrates a number of features that really make the grid malleable and useful for entering, editing, and storing columns of data. First, the look is adjusted by changing the edges of each field style. To enable all the new features, an "update" function is created to run the line of code from the previous example which creates the "q" block of data from text displayed in every cell of the grid. In every case, the data is collected and stored in the variable "q", and the desired operation is performed on that block (adding and removing rows or data, extracting vertical columns of data, saving and loading the data to/from files on the hard drive, etc.). After the data block has been changed by an operation, the entire layout is unviewed and rebuilt using the new data (i.e., the "q" data is reassigned to the initial "x" block). The code is rerun by labeling the entire script "qq" and using the "do" function to re-evaluate it. The final button demonstrates how to collect and display a history of user edits.

x: copy [] for i 1 179 1 [append x reduce [i random "abcd"]]

update: does [q: copy [] foreach face g/pane/pane [append q face/text]]
do qq: [grid: copy [across space 0]
forskip x 2 [append grid compose [
    field (form x/1) 40 edge none 
    field (form x/2) 260 edge [size: 1x1] return
]]
view center-face gui: layout [across space 0
    g: box 300x290 with [pane: layout/tight grid pane/offset: 0x0]
    slider 16x290 [
        g/pane/offset/y: g/size/y - g/pane/size/y * value show g
    ]
    return btn "Add" [
        row: (to-integer request-text/title "Insert at Row #:") * 2 - 1
        update insert at q row ["" ""] x: copy q unview do qq
    ]
    btn "Remove" [
        row: (to-integer request-text/title "Row # to delete:") * 2 - 1
        update remove/part (at q row) 2 x: copy q unview do qq
    ]
    btn "Col 1" [update editor extract q 2]
    btn "Col 2" [update editor extract/index q 2 2]
    btn "Save" [update save to-file request-file/save q]
    btn "Load" [x: load to-file request-file do qq]
    btn "History" [
        m: copy "ITEMS YOU'VE EDITED:^/^/" update for i 1 (length? q) 1 [
            if (to-string pick x i) <> (to-string pick q i) [
                append m rejoin [pick x i " " pick q i newline]
            ]
        ] editor m 
    ]
]]

This final example clarifies how to add additional columns, how to use GUI widgets other than fields to display the data (text widgets, in this case), how to make the widgets perform any variety of actions, and how to get data from the grid when not every widget has text on its face. It also demonstrates some additional changes to the look of the grid.

x: copy [] for i 1 99 1 [append x reduce [i random 99x99 random "abcd"]]

grid: copy [origin 0x0 across space 0x0]
forskip x 3 [
    append grid compose [
        b: box 520x26 either (remainder((index? x)- 1)6)= 0 [white][beige]
        origin b/offset
        text bold 180 (form x/1)
        text 120 center blue (form x/2) [alert face/text]
        text 180 right purple (form x/3) [face/text: request-text] return
        box 520x1 green return
    ]
]
view center-face layout [
    across space 0  
    g: box 520x290 with [pane: layout grid pane/offset: 0x0]
    scroller 16x290 [
        g/pane/offset/y: g/size/y - g/pane/size/y * value / 2 show g
    ]
    return box 1x10 return  ; just a spacer
    btn "Get Data Block" [
        q: copy [] 
        foreach face g/pane/pane [
            if face/style = 'text [append q face/text]
        ]
        editor q
    ]
]

These examples are useful for lists that contain ~1000 or fewer rows of data. For displays with grids larger than that, one of REBOL's other listview options should be used.

17.22 RebGUI

REBOL's VID dialect ("view layout []"), is one of the language's most attractive features. The ability to create GUI windows on multiple operating systems, with as little as 1 line of code, is practical for creating many sorts of applications. "RebGUI" is a third party GUI toolkit built on REBOL/View which replicates many of the basic components in VID, and upgrades/adds to the concept with many desirable features:

  1. Modern look and feel.
  2. Many powerful and useful new widgets and built-in functions: resizable tables (data grids) with automatic column sorting, trees, menus, tab and scroll panels, group boxes, tool-bars, spreadsheet, pie-chart and chat widgets, new requestors, native undo/redo, spellcheck, and translate functions (with many provided language dictionaries) for text widgets, etc.
  3. Simple and elegant syntax (similar to VID).
  4. Full documentation and demo code for all widgets.
  5. Super simple notation to handle automatic alignment and layout of widgets in resized windows.
  6. Config file to easily manage user settings for global UI sizes, colors, behaviors, and effects of all widgets. A built-in native requestor is also provided to adjust all these settings.
  7. Automatic handling of window close events.
  8. User assignable function key actions.
  9. Easy, automatic handling of multiple user languages.
  10. Well designed object structure to access every widget, function, and feature (and containing all necessary help information, built in).
  11. The entire system compresses to just over 30k.

VID is great for building quick scripts, and many of the features found in RebGUI have been created elsewhere as VID add-ons. The menu system and listview widget described earlier in this text, for example, are more powerful than those found in RebGUI. Close events and spell checking can also be handled in other ways described earlier in this text. But for most types of applications, RebGUI provides a single, simple, integrated way to build applications with all the most commonly needed user interface features. It uses a simple, consistent language structure, and provides a clean, modern looking visual design.

RebGUI is available at http://www.dobeash.com/download.html, and several tutorials are available at http://www.dobeash.com/rebgui.html. A mirror of the required files in version 117 is available at http://musiclessonz.com/rebol_tutorial/rebgui.zip. You can also download RebGUI directly within REBOL, using the built in Viewtop. To open the Viewtop, type "desktop" into the REBOL interpreter, then click REBOL -> Demos -> RebGUI. That will download the main "rebgui.r" include file, along with the "RebDoc.r" help program, the "tour.r" demo program, and some supporting graphic images. The downloaded package will automatically run tour.r, which demonstrates many of RebGUI's features. Be sure to click the "RebDOC" button to view all the documentation necessary to use RebGUI.

All you need to use RebGUI is %rebgui.r. Copy it to an accessible folder and include the line "do %rebgui.r" (with its path, if necessary), and then you can use all the built in widgets and functions in RebGUI. A quick and dirty way to do this in Windows is to run the "request-file" function in REBOL, then click Public -> www.Dobeash.com -> RebGUI, right click rebgui.r and paste it into a folder of your choice. You can also use the following script to copy it to any folder:

write to-file request-file/file/title/save %rebgui.r "Save As:" {
    } read view-root/public/www.dobeash.com/RebGUI/rebgui.r

If you're going to use RebGUI regularly, it's a good idea to copy it directly into your main REBOL install directory (the default folder is c:\program files\rebol\view).

To build your first RebGUI interface, after running the RebGUI demo, try the following code:

do view-root/public/www.dobeash.com/RebGUI/rebgui.r
display "Test" [button "Click Me" [alert "Clicked"]]
do-events

Notice that "view layout" has been replaced with "display". This function always requires some title text. Notice also that "do-events" must be included after your RebGUI code to activate the GUI.

Once you've included %rebgui.r, you can try any of the built-in widgets and functions:

display "" [area] do-events  ; the "area" widget

Notice that the area widget above has built-in undo/redo features using [CTRL]-Z and [CTRL]-Y (REBOL's native "view layout [area]" does not have any undo/redo capability). A built-in spellchecker can also be activated using [CTRL]-S! To use the spellchecker, you need to download a dictionary from http://www.dobeash.com/RebGUI/dictionary, and unzip it into %view-root/public/www.dobeash.com/RebGUI/dictionary/ (or in the /dictionary subdirectory of wherever rebgui.r is located).

Take a look at a few of the other great widgets built into RebGUI:

do %rebgui.r  ; be sure to include the path, if necessary

display "Pie Chart" [pie-chart data ["VID" yellow 19 "RebGUI" red 81]]
do-events

display "Spreadsheet" [
    sheet options [size 7x7] data [a1 "very " a2 "cool" a3 "=join a1 a2"]
]
do-events

display "Chat" [
    chat data ["Nick" blue "I like RebGUI" yellow 20-sep-2009/1:00]]
do-events

display/maximize "Menu" [
    menu data [
        "File" [
             "Open" [request-file]
             "Save" [request-file]
         ] 
        "About" ["Info" [alert "RebGUI is great!"]]
    ]
]
do-events

You can run the RebDoc.r program to see the syntax required to use any of the other RebGUI widgets, requestors and functions.

The "/close" refinement of the "display" function lets you set any action(s) you want to run when a GUI window is shut down. This can help avoid data loss from accidental window closure, and provides a way to automatically process data or run other applications when a window is closed:

display/close "" [area] [question "Really Close?"] do-events

Be sure to try the "request-ui" requestor function. It lets you easily adjust the global settings for the overall look and feel of layouts created with RebGUI on your machine. Settings are saved in the file %ui.dat, in the current working directory.

request-ui

RebGUI includes a variety of "span directives" to easily automate resizing of widgets:

These directives automatically set the initial size of a widget:

#L - align the right hand edge of the widget with the adjacent edge
#V - align the base edge of the widget with the adjacent edge
#O - align the left hand edge of the widget with the adjacent edge

("adjacent edge" is the edge of the adjacent widget, or the edge of
the GUI, if there is no adjacent widget.)

These directives automatically adjust the size and position of
a widget when the GUI is resized:

#H - stretch or shrink the widget to fit the window height
#W - stretch or shrink the widget to fit the window width
#X x - move the widget x number of pixels to the right
#Y y - move the widget y number of pixels downward

Here's an example of an area widget that stretches and shrinks to fit a resized GUI window:

display "" [area #HW] do-events

Here's a fully functional, resizable text editor application, with built-in undo/redo, spell checking, and close event handling:

do %rebgui.r
display/maximize/close "Text Editor" [
    menu #LHW data [
        "File" [
             "Open" [x/text: read to-file request-file show x]
             "Save" [write to-file request-file/save x/text]
         ] 
    ] return
    x: area #LHW
] [question "Really Close?"] do-events

Now that's a lot of program for just a little code!

This example demonstrates how to use tab panels and a variety of useful techniques:

display "Tab Panel" [
    main-screen: tab-panel data [
        "Spreadsheet" [
            x: sheet data [
                A1 32 A2 12 A3 "=a1 + a2" A4 "=1.06 * to decimal! a3"
            ]
            a: area
            reverse
            button -1 " Show Data " [x/save-data set-text a x/data]
            button -1 " Quit! " [quit]
        ]
        "VID style"  [
            style -1 data [text bold "Back to Spreadsheet" [
                main-screen/select-tab 1
            ]]
        ]
        action [wait .2 face/color: 230.230.230]  "Text" [
            text "Tabs are a great way to maximize screen real estate."
        ]
        action [wait .2 set-focus z]  "Fields" [
            y: field
            z: field "Edit me"
        ]
    ]
] 
do-events

To really get to know RebGUI, explore its main object "ctx-rebgui":

? ctx-rebgui

The "ctx-rebgui" object is set up much like REBOL's built-in "system/view/vid" object. You can explore it using path notation. Notice that built-in help is included in the "tip" path of each widget:

? ctx-rebgui/widgets/tree/tip

Here's a quick and dirty way to view help for all the RebGUI widgets:

foreach i (find first ctx-rebgui/widgets 'anim) [
    do compose/deep [print rejoin[i" - "(ctx-rebgui/widgets/(i)/tip)"^/"]]
]

Be sure to read the main RebGUI user guide at http://www.dobeash.com/RebGUI/user-guide.html, and the cookbook at http://www.dobeash.com/RebGUI/cookbook.html. Then read through all the info in RebDoc.r, examine the code in tour.r, and get to know your way around ctx-rebgui. You'll likely find that RebGUI is the best choice for GUI layout in many situations.

17.23 RebGUI Apps - Spreadsheet, Rolodex, Member Manager, Editor, POS system

RebGUI contains a spreadsheet widget. Here's a useful spreadsheet application the demonstrates how to use save, load, print and data view features:

do %rebgui.r
display "Spreadsheet" [
    x: sheet options [size 3x3 widths [8 8 10]] data [
        A1 32 A2 12 A3 "=a1 + a2" A4 "=1.06 * to-integer a3"
    ]
    return 
    button "Save" [
        x/save-data
        save to-file request-file x/data
    ]
    button "Load" [
        x/load-data load to-file request-file
    ]
    button "View" [
        x/save-data
        alert form x/data
    ]
    button "Print" [
        save/png %sheet.png to image! x
        browse %sheet.png  ; or call %sheet.png
    ]
] 
do-events

The example below is similar to the "Parts Database" program presented earlier, using RebGUI instead of VID. It should provide a number of practical insights into how to use RebGUI. Notice that the GUI is resizable, the text fields have undo/redo and spellcheck capabilities, requestors are modal, and all the other features of RebGUI are available:

REBOL [title "RebGUI Card File"]

do load-thru http://re-bol.com/rebgui.r

write/append %data.txt ""
database: load %data.txt

display "RebGUI Card File" [
    text 20 "Select:"
    names: drop-list #LW data (sort extract copy database 4) [
        marker: find database pick names/data names/picked
        set-text n copy first marker
        set-text a copy second marker
        set-text p copy third marker
        set-text o copy fourth marker
    ]
    after 2
    text 20 "Name:"        n: field #LW ""
    text 20 "Address:"     a: field #LW ""
    text 20 "Phone:"       p: field #LW ""
    after 1 text "Notes:"  o: area #LW ""
    after 3
    button -1 "Save" [
        if (n/text = "") [alert "You must enter a name." return]
        if find (sort extract copy database 4) copy n/text [
            either true = question "Overwrite existing record?" [
               remove/part (find database n/text) 4
            ] [return]
        ]
        database: repend database [
            copy n/text copy a/text copy p/text copy o/text
        ]
        save %data.txt database
        set-data names (sort extract copy database 4)
        set-text names copy n/text
    ]
    button -1 "Delete" [
        if true = question rejoin ["Delete " copy  n/text "?"] [
            remove/part (find database n/text) 4
            save %data.txt database
            set-data names (sort extract copy database 4)
            set-values face/parent-face ["" "" "" "" ""]
        ]
    ]
    button -1 "New" [
            set-values face/parent-face ["" "" "" "" ""]
    ]
]
do-events

Here's a useful RebGUI text/code editor:

REBOL []

unless exists? %ui.dat [
    write %ui.dat read http://re-bol.com/ui-editor.dat
]
do load-thru http://re-bol.com/rebgui.r    ; Build#117
; do %rebgui.r

filename: %temp.txt
make-dir %./edit_history/

backup: does [
    if ((length? x/text) > 0) [
        write rejoin [
            %./edit_history/ 
             last split-path filename 
             "_" now/date "_"
             replace/all form now/time ":" "-"
        ] x/text
    ]
]
ctx-rebgui/on-fkey/f5: does [
    backup
    write filename x/text
    launch filename
]

display/maximize/close "RebGUI Editor" [
    tight
    menu #LW data [
        "File" [
            "  New  " [
                if true = question "Erase Current Text?" [
                    backup
                    filename: %temp.txt set-text x copy ""
                ]
            ]
            "  Open  " [
                filetemp: to-file request-file/file filename
                if filetemp = %none [return]
                backup
                set-text x read filename: filetemp
            ]
            "  Save  " [
                backup
                write filename x/text
            ]
            "  Save As  " [
                filetemp: to-file request-file/save/file filename
                if filetemp = %none [return]
                backup
                write filename: filetemp x/text
            ]
            "  Save and Run  " [
                backup
                write filename x/text 
                launch filename
            ]
            "  Print  "  [
                write %./edit_history/print-file.html rejoin [
                    {<}{pre}{>} x/text {<}{pre}{>}
                ]
                browse %./edit_history/print-file.html
            ]
            "  Quit  " [
                if true = question "Really Close?" [backup quit]
            ]
        ]
        "Options" [
            "  Appearance  " [request-ui]
        ]
        "Help" [
            "  Shortcut Keys  " [
                alert trim {
                    F5:       Save and Run
                    Ctrl+Z:   Undo
                    Ctrl+Y:   Redo
                    Esc:      Undo All
                    Ctrl+S:   Spellcheck
                }
            ]
        ] 
    ] return
    x: area #LHW
] [
    if true = question "Really Close?" [backup quit]
]

do-events

Here's a user management script, inspired by the tutorial at http://snappmx.com:

REBOL [title: "RebGUI User List Demo"]

do load-thru http://re-bol.com/rebgui.r    ; Build#117  ; do %rebgui.r
unless exists? %snappmx.txt [
    save %snappmx.txt [
        "user1" "pass1" "Bill Jones" "%bill--site--com" "Bill LLC" 
        "user2" "pass2" "John Smith" "%john--mail--com" "John LLC"
    ]
]
database: load %snappmx.txt
login: request-password
found: false
foreach [userid password name email company] database [
    either (login/1 = userid) and (login/2 = password) [found: true] []
]
if found = false [alert "Incorrect Login." quit]
add-record: does [
    display/dialog "User Info" [
        text 20 "User:" f1: field return
        text 20 "Pass:" f2: field return
        text 20 "Name:" f3: field return
        text 20 "Email:" f4: field return
        text 20 "Company:" f5: field reverse
        button -1 #XY " Clear " [clear-fields]
        button -1 #XY " Add " [add-fields]
    ]
]
edit-record: does [
    display/dialog "User Info" [
        text 20 "User:" f1: field (form pick t/selected 1) return
        text 20 "Pass:" f2: field (form pick t/selected 2) return
        text 20 "Name:" f3: field (form pick t/selected 3) return
        text 20 "Email:" f4: field (form pick t/selected 4) return
        text 20 "Company:" f5: field (form pick t/selected 5) reverse
        button -1 #XY " Delete " [
            t/remove-row t/picked
            save %snappmx.txt t/data
            hide-popup
        ]
        button -1 #XY " Save " [
            t/remove-row t/picked
            add-fields
            save %snappmx.txt t/data
            hide-popup
        ]
    ]
]
add-fields: does [
    t/add-row reduce [
        copy f1/text copy f2/text copy f3/text copy f4/text copy f5/text
    ]
    save %snappmx.txt copy t/data
]
clear-fields: does [
    foreach item [f1 f2 f3 f4 f5] [do rejoin [{set-text } item {""}]]
]
table-size: system/view/screen-face/size/1 / ctx-rebgui/sizes/cell
display/maximize "Users" [
    t: table table-size #LWH options [
        "" left .0  "" left .0   ; don't show the first 2 fields
        "Name" center .33  "Email" center .34  "Company" center .34
    ] data database [edit-record]
    reverse
    button -1 #XY " Add " [add-record]
]
do-events

Here is a point of sale system (sales checkout, receipt printer, and data storage system) written using RebGUI. Note that the username and password info in the posp.db file should be created and read using a separate method, and encrypted. The example posp.db file is created here as a demonstration. Note also that the first field in the layout is designed to accept input from a keyboard wedge bar code scanner, with data in the format: item (space) booth (space) price (inserted [ENTER] key character). Using this format, and the automatic refocus upon entry, the user can continually scan multiple items into the system:

REBOL [title: "POINT OF SALE SYSTEM"]

write %posp.db {["username" "password"] ["username2" "password2"]} ; etc.
make-dir %./receipts/
write/append %./receipts/deleted.txt ""  ; create file if not exists

unless exists? %scheme_has_changed [
    write %ui.dat decompress #{
        789C9552CB92A3300CBCE72BBCDCA18084995A7E652A078115F08EB129592C33
        7FBFC24E32CC2387A5EC2A49ED6EB56C267845E5BB3FD8F32FF57250F2CD3060
        ABEAA629E23E95B1CAF8C6AD7A3A1571A5D28813E6D60CA32055752AAAE67751
        97CF3B5003BDB6EA5817CF821E9B8804067E484BE04F34BFB035EE4EACCB5371
        DD9FE044AD8E4FC5751FCE6AFA3E648FD6B62A51516F035731BE78B7B9AAEF49
        3EE2D5693A3CC02CCD63B8F5DB8CC464021A8CBB49066B3492901EB4879E8D77
        B92C74BC1D7CD1E467992DB0D8319CA28B41ABE53D42583D691566E31C521438
        7F9161E844241276780F84BCC117DF2F410E480E7BFCBDB7A697FA407E99F3CE
        BF493787568511919588E631DF5146131F602FFA1F8645B1437D35A2BA85D93B
        F5317A8C9810BF5DC240E6A1F0CF374CE4D790B31F507E45B9E10BD8801122D0
        6633DEEC5E3CFB8BA4C14176AF6D936540066CA6B2DE2F649094C35532361386
        EC0B270D18660B61CC355A78BFFD53ECBD6533DF8A655BCA4AD08A9D366E905E
        4C4B72B71AA7FDDA2AE71D1ECEFF004BE40F38A0030000
    }
]

do http://re-bol.com/rebgui.r

do login: [
    userpass: request-password
    if (length? userpass) < 2 [quit]
    posp-database: to-block read %posp.db
    logged-in: false
    foreach user posp-database [
        if (userpass/1 = user/1) and (userpass/2 = user/2) [
            logged-in: true
        ]
    ]
    either logged-in = true [] [
        alert "Incorrect Username/Password"
        do login
    ]
]
calculate-totals: does [
    tax: .06
    subtotal: 0
    foreach [item booth price] pos-table/data [
        subtotal: subtotal + to decimal! price
    ]
    set-text subtotal-f subtotal
    set-text tax-f (round/to (subtotal * tax) .01)
    set-text total-f (round/to (subtotal + (subtotal * tax)) .01)
    set-focus barcode
]
add-new-item: does [
    if ("" = copy f1/text) or ("" = copy f2/text) or (error? try [
        to-decimal copy f3/text
    ]) [
        alert trim/lines {You must enter a proper Item Description,
            Booth Number, and Price.}
        return
    ]
    pos-table/add-row/position reduce [
        copy f1/text copy f2/text copy f3/text
    ] 1
    calculate-totals
]
print-receipt: does [
    if empty? pos-table/data [
        alert "There's nothing to print." return
    ]
    html: copy rejoin [
        {<html><head><title>Receipt</title></head><body>
        <table width=40% border=0 cellpadding=0><tr><td>
        <h1>Business Name</h1>
        123 Road St.<br>
        City, State 98765<br>
        123-456-7890
        </td></tr></table><br><br>
        <center><table width=80% border=1 cellpadding=5>
        <tr>
        <td width=60%><strong>Item</strong></td>
        <td width=20%><strong>Booth</strong></td>
        <td width=20%><strong>Price</strong></td></tr>}
    ]    
    foreach [item booth price] pos-table/data [
        append html rejoin [
            {<tr><td width=60%>} item 
            {</td><td width=20%>} booth 
            {</td><td width=20%>} price {</td></tr>}
        ]
    ]
    append html rejoin [
        {<tr><td width=60%></td><td width=20%><strong>SUBTOTAL:
        </strong></td><td width=20%><strong>}
        copy subtotal-f/text 
        {</strong></td></tr>}
    ]
    append html rejoin [
        {<tr><td width=60%></td><td width=20%><strong>TAX:
        </strong></td><td width=20%><strong>}
        copy tax-f/text 
        {</strong></td></tr>}
    ]
    append html rejoin [
        {<tr><td width=60%></td><td width=20%><strong>TOTAL:
        </strong></td><td width=20%><strong>}
        copy total-f/text 
        {</strong></td></tr>}
    ]
    append html rejoin [
        {</table><br>Date: <strong>} now/date 
        {</strong>, Time: <strong>} now/time 
        {</strong>, Salesperson: } userpass/1
        {</center></body></html>}
    ]
    write/append to-file saved-receipt: rejoin [
        %./receipts/
        now/date "_"
        replace/all copy form now/time ":" "-"
        "+" userpass/1 
        ".html"
    ] html
    browse saved-receipt
]
save-receipt: does [
    if empty? pos-table/data [
        alert "There's nothing to save." return
    ]
    if allow-save = false [
        unless true = resaving: question trim/lines {
            This receipt has already been saved.  Save again?
        } [
            if true = question "Print another copy of the receipt?" [
                print-receipt
            ]
            return
        ]
    ] 
    if resaving = true [
        resave-file-to-delete: copy ""
        display/dialog "Delete" compose [
            text 150 (trim/lines {
                IMPORTANT - DO NOT MAKE A MISTAKE HERE!  
                Since you've made changes to an existing receipt,
                you MUST DELETE the original receipt.  The original
                receipt will be REPLACED by the new receipt (The
                original data will be saved in an audit history file,
                but will not appear in any future seaches or totals.)
                Please CAREFULLY choose the original receipt to DELETE:
            })
            return
            tl1: text-list 150 data [
                "I'm making changes to a NEW receipt that I JUST SAVED" 
                "I'm making changes to an OLD receipt that I've RELOADED"
            ] [
                resave-file-to-delete: tl1/selected
                hide-popup
            ]
            return
            button -1 "Cancel" [
                resave-file-to-delete: copy "" 
                hide-popup
            ]
        ]
        if resave-file-to-delete = "" [
            resaving: false
            return
        ]
        if resave-file-to-delete = trim/lines {
            I'm making changes to a NEW receipt that I JUST SAVED
        }  [
            the-file-to-delete: saved-file
        ]
        if resave-file-to-delete = trim/lines {
            I'm making changes to an OLD receipt that I've RELOADED
        } [
            the-file-to-delete: loaded-receipt
        ]
        if not question to-string the-file-to-delete [return]
        write %./receipts/deleted--backup.txt read %./receipts/deleted.txt
        write/append %./receipts/deleted.txt rejoin [
            newline newline newline
            to-string the-file-to-delete
            newline newline
            read the-file-to-delete
        ]
        delete the-file-to-delete
        alert "Original receipt has been deleted, and new receipt saved."
        resaving: false
    ]
    if true = question "Print receipt?" [print-receipt]
    saved-data: mold copy pos-table/data
    write/append to-file saved-file: copy rejoin [
        %./receipts/
        now/date "_"
        replace/all copy form now/time ":" "-"
        "+" userpass/1 
        ".txt"
    ] saved-data
    splash compose [
        size: 300x100
        color: sky
        text: (rejoin [{^/      *** SAVED ***^/^/      } saved-file {^/}])
        font: ctx-rebgui/widgets/default-font
    ]
    wait 1
    unview
    allow-save: false
    if true = question "Clear and begin new receipt?" [clear-new]
]
load-receipt: does [
    if error? try [
        loaded-receipt: to-file request-file/file/filter %./receipts/
            ".txt" "*.txt"
    ] [
        alert "Error selecting file"
        return
    ]
    if find form loaded-receipt "deleted" [
        alert "Improper file selection" 
        return
    ]
    if error? try [loaded-receipt-data: load loaded-receipt] [
        alert "Error loading data"
        return
    ]
    insert clear pos-table/data loaded-receipt-data
    pos-table/redraw
    calculate-totals
    allow-save: false
]
search-receipts: does [
    search-word: copy request-value/title "Search word:" "Search"
    ; if search-word = none [return]
    found-files: copy []
    foreach file read %./receipts/ [
        if find (read join %./receipts/ file) search-word [
            if (%.txt = suffix? file) and (file <> %deleted.txt) [
                append found-files file
            ]
        ]
    ]
    if empty? found-files [alert "None found" return]
    found-file: request-list "Pick a file to open" found-files
    if found-file = none [return]
    insert clear pos-table/data (
        load loaded-receipt: copy to-file join %./receipts/ found-file
    )
    pos-table/redraw
    calculate-totals
    allow-save: false
]
clear-new: does [
    if allow-save = true [
        unless (true = question "Erase without saving?") [return]
    ]
    foreach item [barcode f1 f2 f3 subtotal-f tax-f total-f] [
        do rejoin [{clear } item {/text show } item]
    ]
    clear head pos-table/data
    pos-table/redraw
    allow-save: true
]
change-appearance: does [
    request-ui
    if true = question "Restart now with new scheme?" [
        if allow-save = true [
            if false = question "Quit without saving?" [return]
        ]
        write %scheme_has_changed ""
        launch %pos.r  ; EDIT
        quit
    ]
]
title-text: "Point of Sale System"
if system/version/4 = 3 [
    user32.dll: load/library %user32.dll
    get-tb-focus: make routine! [return: [int]] user32.dll "GetFocus"
    set-caption: make routine! [
        hwnd [int] 
        a [string!]  
        return: [int]
    ] user32.dll "SetWindowTextA"
    show-old: :show
    show: func [face] [
        show-old [face]
        hwnd: get-tb-focus
        set-caption hwnd title-text
    ]
]

allow-save: true
resaving: false
saved-file: ""
loaded-receipt: ""

screen-size: system/view/screen-face/size
cell-width: to-integer (screen-size/1) / (ctx-rebgui/sizes/cell)
cell-height: to-integer (screen-size/2) / (ctx-rebgui/sizes/cell)
table-size: as-pair cell-width (to-integer cell-height / 2.5)
current-margin: ctx-rebgui/sizes/margin
top-left: as-pair negate current-margin negate current-margin

display/maximize/close "POS" [
    at top-left #L main-menu: menu data [
        "File" [
            "     Print      " [print-receipt]
            "     Save       " [save-receipt]
            "     Load       " [load-receipt]
            "     Search     " [search-receipts]
        ]
        "Options" [
            "     Appearance     " [change-appearance]
        ] 
        "About" [
            "     Info     " [
                alert trim/lines {
                    Point of Sale System. 
                    Copyright  2010 Nick Antonaccio. 
                    All rights reserved.
                }
            ]
        ]
    ]
    return
    barcode: field #LW tip "Bar Code" [
        parts: parse/all copy barcode/text " "
        set-text f1 parts/1
        set-text f2 parts/2
        set-text f3 parts/3
        clear barcode/text
        add-new-item
    ]
    return
    f1: field tip "Item" 
    f2: field tip "Booth" 
    f3: field tip "Price (do NOT include '$' sign)" [
        add-new-item 
        set-focus add-button
    ]
    add-button: button -1 "Add Item" [
        add-new-item 
        set-focus add-button
    ]
    button -1 #OX "Delete Selected Item" [
        remove/part find pos-table/data pos-table/selected 3
        pos-table/redraw
        calculate-totals
    ]
    return
    pos-table: table (table-size) #LWH options [
        "Description" center .6
        "Booth" center .2
        "Price" center .2
    ] data []
    reverse
    panel sky #XY data [
        after 2
        text 20 "Subtotal:" subtotal-f: field 
        text 20 "     Tax:" tax-f: field
        text 20 "   TOTAL:" total-f: field
    ]
    reverse
    button -1 #XY "Lock" [do login]
    button -1 #XY "New" [clear-new]
    button -1 #XY "SAVE and PRINT" [save-receipt]
    do [set-focus barcode]
] [question "Really Close?"]

do-events

17.24 Creating PDF files using pdf-maker.r

PDF is a standard file format used to display and print document content in exactly the same way on different computer platforms. In Windows and other operating systems, the PDF reader by Adobe is often installed by default. Other free PDF readers such as Foxit, Sumatra, and PDF-Xchange allow you to view and print PDF documents. Openoffice can be used to create, convert, and save various document formats (i.e. MS Word and other word processor formats) to PDF, so that they are viewable/printable in the exact same visual layout, on any computer.

Gabriele Santilli has created a REBOL pdf-maker script that generates universally readable and printable PDF files directly from REBOL code. The official documentation is available at http://www.colellachiara.com/soft/Misc/pdf-maker-doc.pdf (the REBOL source used to create that PDF document is available at http://www.colellachiara.com/soft/Misc/pdf-maker-doc.r). Pdf-maker.r is a complete, self contained multi-platform solution for creating PDFs. No other software is required to create PDFs with REBOL.

The basic functionality of pdf-maker.r is very simple. Import pdf-maker.r with the "do" function (or simply include it directly in your code). Next, run the "layout-pdf" function, which takes one block as a parameter, and write its output to a .pdf file using the "write/binary" function. Inside the block passed to the "layout-pdf" function, a variety of formatting functions can be included to layout text, images, and manually generated graphics. Here's a basic example of the format, with one simple text layout function:

do http://www.colellachiara.com/soft/Misc/pdf-maker.r
write/binary %example.pdf layout-pdf [[textbox ["Hello PDF world!"]]]

; To open the created document in your default PDF viewer:

call %example.pdf

Here's a more complex example that creates a multi-page PDF file and demonstrates many of the basic capabilities of pdf-maker.r. Separate page content is contained in separate sub-blocks. All coordinates are written in MILLIMETER format:

REBOL [title: "pdf-maker example"]

do http://www.colellachiara.com/soft/Misc/pdf-maker.r

write/binary %example.pdf layout-pdf compose/deep [
    [
        page size 215.9 279.4  ; American Letter Size!!!
        textbox ["Here is page 1.  It just contains this text."]
    ] 
    [
        textbox 55 55 90 100 [
            {Here's page 2.  This text box contains a starting
             XxY position and an XxY size.  Coordinates are in
             millimeters and extend from the BOTTOM LEFT of the
             page (this box extends from starting point 55x55
             and is 90 mm wide, 100 mm tall).

             *** NOTE ABOUT PAGE SIZES - IMPORTANT!!! *** 

             All the following page sizes are the default ISO A4,
             or 211297 mm.  That is SLIGHTLY SMALLER than the
             standard American Letter page size.  If you are
             printing on American Letter sized paper, be sure to
             manually set your paper size, as is done on the first
             page of this example.}
        ]
    ]
    [
        textbox 0 200 200 50 [
            center font Helvetica 10.5
            {This is page 3.  The text inside this box is centered
             and formatted using Helvetica font, with a character
             size of 10.5 mm.}
        ]
    ]
    [
        apply rotation 20 translation 35 150 [
            textbox 4 4 200 20 [
                {This is page 4.  The textbox is rotated 20 degrees
                 and translated (moved over) 35x150 mm.  Graphics
                 and images can also be rotated and translated.}
            ]
        ]
    ]
    [
        textbox 5 200 200 40 [
            {Here's page 5.  It contains this textbox and several
             images.  The first image is placed at starting point
             50x150 and is 10mm wide by 2.4mm tall.  The second
             image is 2x bigger and rotated 90 degrees.  The last
             image is placed at starting point 100x150 and is
             streched to 10x its size.  Notice that this ENTIRE
             layout block has been evaluated with compose/deep to
             evaluate the images in the following parentheses.}
        ]
        image 50 150 10 2.4 (system/view/vid/image-stock/logo)
        image 50 100 20 4.8 rotated 90 
            (system/view/vid/image-stock/logo)
        image 100 150 100 24 (system/view/vid/image-stock/logo)
    ]
    [
        textbox [
            {This page contains this textbox and several generated
             graphics:  a line, a colored and filled box with a
             colored edge, and a circle.}
        ]
        line width 3  20 20 100 50   ; starting and ending XxY positions
        solid box edge width 0.2 edge 44.235.77 150.0.136 100 67 26 16
        circle 75 50 40   ; starting point 75x50, radius 40mm
    ]
]

call %example.pdf

The compose/deep evaluation is very important when using computed values in PDF layouts. Take a look at the following example that uses computed coordinates and image values:

do http://www.colellachiara.com/soft/Misc/pdf-maker.r
xpos: 50  ypos: 200  offset: 5  
size: 5  width: (10 * size)  height: (2.4 * size)
page1: compose/deep [[
    image 
        (xpos + offset) (ypos + offset)
        (width) (height)
        (system/view/vid/image-stock/logo)
]]
write/binary %example.pdf layout-pdf page1
call %example.pdf

Here is a program that I wrote for guitar students. It prints out fretboard note diagrams that can be cut out, wrapped around, and taped directly to guitar fretboards of specific varied sizes. The pdf-maker script is included in compressed, embedded format:

REBOL [title:  "Guitar Fretboard Note Overlay Printer"]

chosen-scale: none
view center-face layout [
    h1 "Fretboard length:"
    text-list "25.5" "27.67" "30" [
        chosen-scale: join "scale" value
        unview
        alert rejoin [
            "Now printing " 
            value 
            " inch scale fretboard overlay to 'notes.pdf'"
        ]
    ]
]

notes: [
    [{F}{C}{ }{ }{ }{F}]
    [{ }{ }{A}{E}{B}{ }]
    [{G}{D}{ }{F}{C}{G}]
    [{ }{ }{B}{ }{ }{ }]
    [{A}{E}{C}{G}{D}{A}]
    [{ }{F}{ }{ }{ }{ }]
    [{B}{ }{D}{A}{E}{B}]
    [{C}{G}{ }{ }{F}{C}]
    [{ }{ }{E}{B}{ }{ }]
    [{D}{A}{F}{C}{G}{D}]
    [{ }{ }{ }{ }{ }{ }]
    [{E}{B}{G}{D}{A}{E}]
]

scale25.5: [
    36.35 70.66 103.05 133.62 162.47 189.71 215.41 239.67 262.58 284.19
    304.59 323.85 342.03 359.18 375.38 390.66 405.09 418.70 431.56 443.69
    455.14 465.95 476.15 485.77
]

scale27.67: [
    39.45 76.68 111.82 144.99 176.30 205.85 233.74 260.07 284.92 308.38
    330.51 351.41 371.13 389.75 407.32 423.91 439.56 454.34 468.28 481.45
    493.87 505.60 516.67 527.11
]

scale30: [
    42.77 83.14 121.24 157.20 191.15 223.18 253.43 281.97 308.91 334.34
    358.34 381.00 402.38 422.57 441.62 459.60 476.57 492.59 507.71 521.99
    535.46 548.17 560.17 571.50
]

x: 40  line-width: 30  text-width: 4  height: 5

make-overlay: does [
    page1: copy [
        textbox 40 0 4 6 [center font Helvetica 5 "E"]
        textbox 45 0 4 6 [center font Helvetica 5 "B"]
        textbox 50 0 4 6 [center font Helvetica 5 "G"]
        textbox 55 0 4 6 [center font Helvetica 5 "E"]
        textbox 60 0 4 6 [center font Helvetica 5 "A"]
        textbox 65 0 4 6 [center font Helvetica 5 "E"]
    ]
    output: copy []
    for i 1 10 1 [
        y: do compose [pick (to-word chosen-scale) i]
        notes-at-fret: pick notes i
        append page1 compose/deep [
            line width 4 (x) (y) (x + line-width) (y)
            textbox (x) (y - 10) (text-width) (height + 1) [
                center font Helvetica (height) (notes-at-fret/1)
            ]
            textbox (x + 5) (y - 10) (text-width) (height + 1) [
                center font Helvetica (height) (notes-at-fret/2)
            ]
            textbox (x + 10) (y - 10) (text-width) (height + 1) [
                center font Helvetica (height) (notes-at-fret/3)
            ]
            textbox (x + 15) (y - 10) (text-width) (height + 1) [
                center font Helvetica (height) (notes-at-fret/4)
            ]
            textbox (x + 20) (y - 10) (text-width) (height + 1) [
                center font Helvetica (height) (notes-at-fret/5)
            ]
            textbox (x + 25) (y - 10) (text-width) (height + 1) [
                center font Helvetica (height) (notes-at-fret/6)
            ]
        ]
    ]
    append/only output page1
    write/binary %notes.pdf layout-pdf output
    alert "Done"
]

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}

make-overlay

Several articles about pdf-maker are available at rebolfrance.info: first translated by Google, second translated by Google.

17.25 Bar Codes

Bar codes are used in many business applications to speed data entry and to reduce input errors. It would be foolish to build a point of sale system or an inventory management system without using bar code technology.

Reading bar code data into the computer is extremely easy. USB scanners (hardware devices) work just like keyboards. Plug them into the computer, and anything they read from a bar code will be entered as plain text into your application, just as if the text was typed by hand.

Insert a field widget into your GUI, focus it automatically if necessary, and you're in business with bar codes. Add some error checks, save to a file, select from a data block, etc., as needed:

REBOL [title "Bar Code Reader"]
view layout [
    text "Plug in your scanner and scan:"
    f1: field [
        if f1/text <> "" [
            write/append %barcodes.txt rejoin [
                copy f1/text
                newline
            ]
        ]
        if "recall" = select ["123456" "ok" "234567" "recall"] f1/text [
            alert "That item has been recalled!"
        ]
        f1/text: copy ""
        focus f1
    ]
    do [focus f1]
    btn "View Scanned Bar Codes" [editor %barcodes.txt]
]

Printing bar codes requires some more code. The scripts at http://www.rebol.org/view-script.r?script=code39.r and http://www.rebol.org/view-script.r?script=ean13.r demonstrate how to print several common bar code formats to images.

The following program takes a given string and XxY coordinate (in millimeters), and outputs a PDF file containing a printable bar code at the given position. The bar code algorithm is derived directly from Bohdan Lechnowsky's "code39.r", and the PDF is generated using Gabriele Santilli's "pdf-maker.r". This script was created because images output by the original code39.r script would become blurred when inserted and resized by pdf-maker.r. Here, the bars are rendered as lines, directly in pdf-maker dialect. The images generated are crisp and easily scan-able:

REBOL [title: "PDF Bar Code Generator"]

text-string: "item2342"
x-offset: 10    ; millimeters from the left edge of the page
y-offset: 257   ; millimeters from the bottom edge of the page

create-pdf-barcode: func [barcode-string xshift yshift] [
    barcode-width: .3  barcode-height: 12  
    code39: first to-block decompress #{
    789C5D93490EC2400C04EF794514C10504D8EC1CD9F77D07F1FF6F30C9C4E3F6
    200529E54EA91D866F92BA4FC699BB989828FF6277EB793BE7EE3EE69D322F03
    E15D9F27629BEFA9DFE4FBEA377C103CC520F021F684FC087B0227EC037C2C9E
    F209E113F1447C1AF6F503E1B3D2CF517E1EFC36BF087ECB97E221BBEF0A7B42
    7E8D3D816FB00FF0AD7A8A89F09D7A0CDFC3BEF940F841FD267F847D317F827D
    919FC3BE6C3C17E889F92BF4447E833EC8EFDE43A212FE28F2C4317F4A9EED79
    7E95F9F83CBFD56FF21FF51BDE081EFBFB36B127E453EC09BC867D80578447E7
    B3051CDF4F5DFB185ED5FF9DE7C9EF0F6518AA1B22040000
    }
    convfrom: rejoin ["*" barcode-string "*"]
    pdf-dialect-out: copy []
    x: 0
    foreach char convfrom [
        pattern: select code39 form char
        foreach bit pattern [
            x: x + 1
            if bit = #"1" [
                append pdf-dialect-out compose [
                    line width (barcode-width)
                    line
                    (
                        (x * barcode-width) + xshift
                    ) (
                        yshift
                    )
                    (
                        (x * barcode-width) + xshift
                    ) (
                        yshift + barcode-height
                    )
                ]
            ]
        ]
        x: x + 1
    ]
    return pdf-dialect-out
]

do http://www.colellachiara.com/soft/Misc/pdf-maker.r 
barcode-layout: copy []
current-barcode-page: copy [page size 215.9 279.4 offset 0 0]
append current-barcode-page create-pdf-barcode 
    text-string x-offset y-offset

; The following block is not necessary.  It just adds human readable text
; to the printout:

append current-barcode-page compose/deep [
    textbox 
    (x-offset - 9.5) (y-offset - 8)
    56 8
    [
        center font Helvetica 3 
        (mold text-string)
    ]
]

append/only barcode-layout current-barcode-page
write/binary %labels.pdf layout-pdf barcode-layout
call %labels.pdf

; This line is unnecessary - it just lets you read the pdf dialect output:

editor barcode-layout

Here's an function from the Merchants' Village software which prints vendor bar codes on pages of Avery Label paper (30 labels per page), with the option to start printing on any chosen label position on the first page inserted into a printer (to allow continued printing on partially used pages). This example is taken out of a larger RebGUI application, and requires the .PDF module. Even though it's taken out of context, the logic is useful for anyone who wants to print pages of bar code labels:

print-bar-codes: does [
    bar-code-data-to-print: copy []
    bar-code-human-readable-to-print: copy []
    either true = question "Print bar codes from vendor order file?" [
        if error? try [
            barcode-order: request-file/only
            barcode-order-data: load barcode-order
            temporary-barcode-data: copy second barcode-order-data
        ] [alert "Not a valid bar code order file."]
    ] [
        temporary-barcode-data: (copy pos-table/data)
    ]
    temporary-barcode-data-build: copy []
    foreach [booth item price] temporary-barcode-data [
        new-price: to-decimal copy price
        if new-price < .01  [
            new-price: request-value/type rejoin [
                "Enter Price for " booth ", " item ": "
            ] decimal!
        ]
        append temporary-barcode-data-build reduce [booth item new-price]
    ]
    display/maximize/dialog "Bar Codes" [
        barcode-pos-table: table (table-size) #LWOH options [
            "Booth" center .25
            "Item" center .55
            "Price" center .20
        ] data (copy temporary-barcode-data-build) [
            ; on-click, change the selected line price (request-text)
            ; probe barcode-pos-table/picked
            new-price: request-value/type rejoin [
                "Enter Price for " pick barcode-pos-table/selected 1
                ", " pick barcode-pos-table/selected 2
                ", " pick barcode-pos-table/selected 3 ": "
            ] decimal!
            if new-price = none [return]
            barcode-pos-table/alter-row barcode-pos-table/picked reduce [
                pick barcode-pos-table/selected 1
                pick barcode-pos-table/selected 2
                pick barcode-pos-table/selected 3
                new-price
            ]
            barcode-pos-table/redraw
        ]
        return
        button "Print" #XYO  [
            all-the-barcode-data: copy barcode-pos-table/data
            hide-popup
        ]
    ]
    unless value? 'all-the-barcode-data [return]
    if all-the-barcode-data = none [return]
    foreach [booth item price] all-the-barcode-data [
        bar-code-data: copy ""
        bar-code-human-readable: copy ""
        temp-booth: copy booth
        booth-name-to-print: copy temp-booth
        append bar-code-human-readable rejoin [
            "booth " temp-booth ", item: "
        ]
        if error? try [booth-index: to-integer copy temp-booth] [
            booth-index: 0
        ] 
        append bar-code-data booth-index
        append bar-code-data select [
            1 "  " 2 " " 3 ""
        ] (length? bar-code-data)
        temp-item: copy item
        append bar-code-human-readable join temp-item ", "
        if error? try [item-index: index? find items temp-item] [
            item-index: 0
        ]
        append bar-code-data item-index
        append bar-code-data select [
            4 "    " 5 "   " 6 "  " 7 " " 8 ""
        ] (length? bar-code-data)
        temp-price: to-decimal price
        temp-price-nodot: to-integer (price * 100)
        append bar-code-human-readable rejoin ["$" temp-price]
        append bar-code-data form temp-price-nodot
        append bar-code-data-to-print bar-code-data
        append bar-code-human-readable-to-print bar-code-human-readable
    ] ; probe bar-code-data
    ; Avery Address Label Edges:   left - 5 75 145   right - 71 141 211
    ; tops/bottoms - 13 38.5 64 89.5 115 140 165.5 191 216.5 241.5 267
    barcode-label-positions: [
        5 267    75 267    145 267      5 241.5  75 241.5  145 241.5
        5 216.5  75 216.5  145 216.5    5 191    75 191    145 191
        5 165.5  75 165.5  145 165.5    5 140    75 140    145 140
        5 115    75 115    145 115      5 89.5   75 89.5   145 89.5
        5 64     75 64     145 64       5 38.5   75 38.5   145 38.5 
    ]
    current-barcode-pos: request-value/default/type 
        "Position on page to begin printing: " "1" integer!
    if current-barcode-pos = none [return]
    if current-barcode-pos = "" [return]
    if current-barcode-pos = -1 [return]
    current-barcode-pos: (to-integer current-barcode-pos) * 2 - 1
    barcode-counter: 1
    barcode-list-index: 1
    barcode-layout: copy []
    current-barcode-page: copy [page size 215.9 279.4 offset 2 -17 ]
    loop (length? bar-code-data-to-print) [
        append current-barcode-page compose/deep [
            (create-pdf-barcode 
                (pick bar-code-data-to-print barcode-list-index)
                (pick barcode-label-positions current-barcode-pos)
                (pick barcode-label-positions (current-barcode-pos + 1))
            )
            textbox 
                (pick barcode-label-positions current-barcode-pos)
                ((pick barcode-label-positions 
                    (current-barcode-pos + 1)) - 10)
                56 8
                [
                    font Helvetica 3 
                    (mold pick bar-code-human-readable-to-print
                        barcode-list-index)
                ]
        ]
        barcode-counter: barcode-counter + 1
        barcode-list-index: barcode-list-index + 1
        current-barcode-pos: current-barcode-pos + 2
        if current-barcode-pos > 60 [
            current-barcode-pos: 1
            append/only barcode-layout current-barcode-page
            current-barcode-page: copy [
                page size 215.9 279.4 offset 2 -17
            ]
        ]
    ]
    append/only barcode-layout current-barcode-page
    make-dir %./barcodes/
    write/binary %./barcodes/labels.pdf layout-pdf barcode-layout
    current-barcode-file-name: to-file rejoin [
        "./barcodes/labels--booth_" booth-name-to-print "_" 
        booth-number-login/text "--" now/date "_" 
        replace/all copy form now/time ":" "-"
        ".pdf"
    ]
    write/binary current-barcode-file-name layout-pdf barcode-layout
    either pdf-choice = "none" [
        if error? try [call %./barcodes/labels.pdf] [
            write %pdf-choice.txt "SumatraPDF.exe"
            call rejoin [
                (to-local-file %SumatraPDF.exe) " " 
                (to-local-file %./barcodes/labels.pdf)
            ]
        ]
    ] [
        call rejoin [
            (to-local-file read %pdf-choice.txt) " " 
            (to-local-file %./barcodes/labels.pdf)
        ]
    ]
]

Third party DLLs and other tools such as http://sourceforge.net/projects/openbarcodes/files/ provide useful solutions to printing bar codes of all types.

17.26 Creating .swf Files with REBOL/Flash

Flash is a ubiquitous multimedia format used to deliver graphics, sound, video, games, and entire web sites on the Internet. Flash is already installed on over 90% of all computers connected to the Internet. It is available as a small free plugin for every major web browser, at http://get.adobe.com/flashplayer. There are a variety of other flash players available which can display Flash formatted ".swf" files on mobile devices, on desktop operating systems, and on the web. Flash's ubiquity, power, and comprehensive multimedia features makes it a popular platform for rich media development, especially online.

Flash was originally created by the Macromedia company, and is now owned by Adobe. Adobe's Flash CS4 development package is an expensive and heavy development environment with a significant learning curve, and it requires proficiency in the "Actionscript" language. There are many other commercial and open source offerings that can be used to create flash .swf files, but many of those are oriented to creating simple animations with moving text effects, graphic sweeps, pans, fades, etc.

CS4 is a fantastically powerful tool (the industry standard), but for many Flash development needs, you'll be happy to learn that you don't need to venture outside the REBOL world. REBOLers have their own Flash creation tool available, which is freely downloadable and which does not require any additional languages or development tools to create rich multimedia .swf files. Just do the REBOL/flash script at http://box.lebeda.ws/~hmm/rswf/rswf_latest.r, and you've got a powerful Flash development system at your fingertips.

Using REBOL/flash is simple. The following 3 lines demonstrate the basic process of installing the dialect (DOing the REBOL/flash script file), compiling a downloaded REBOL/flash source code file, and then viewing the compiled .swf file in your browser:

do http://box.lebeda.ws/~hmm/rswf/rswf_latest.r   ; install REBOL/flash
make-swf/save/html http://tinyurl.com/yhex2cf     ; compile the source
browse %starfield1.html                           ; view the created .swf

To begin working with REBOL/flash in earnest, you'll want to save a copy of the REBOL/flash dialect to your hard drive:

write %rswf.r read http://box.lebeda.ws/~hmm/rswf/rswf_latest.r

The file above is a native REBOL program, created by David 'Oldes' Oliva, which takes input in the REBOL/flash dialect (a REBOL mini-language created by Oldes), and which directly outputs Flash .swf files. No other tools (besides the REBOL interpreter) are required to build very powerful Flash applications that you can use on your web site, in desktop presentations, etc.

Here are a few demo examples to download:

examples: [
    http://box.lebeda.ws/~hmm/rswf/examples/swf5/swf5-eyeball.rswf
    http://box.lebeda.ws/~hmm/rswf/examples/swf5/swf5-snow.rswf
    http://box.lebeda.ws/~hmm/rswf/examples/swf5/swf5-starfield2.rswf
]
foreach file examples [write (to-file last split-path file) (read file)]

Those are just several of the 175 code examples at http://box.lebeda.ws/~hmm/rswf. That large collection of code examples represents the full existing documentation for the REBOL/flash dialect. Reading and experimenting with them will help you become familiar with the REBOL/flash API, and will demonstrate how to use the essential building blocks required to accomplish many necessary REBOL/flash development tasks. Note that Oldes' previous REBOL/flash web site is still available at http://oldes.multimedia.cz/swf. That site has a downloadable zip file of all the code examples and some additional older tools such as a swf-to-exe compiler (that site is no longer updated).

After downloading/doing the script at http://box.lebeda.ws/~hmm/rswf/rswf_latest.r, you can compile REBOL/flash source code files into working .swf files using the "make-swf" function. The /save and /html refinements of that function are most typically used, as they generate the HTML needed to insert the Flash object in your own web pages. The make-swf/save/html function creates a fully functional .swf Flash file and the necessary container HTML file in the same folder as rswf.r. Here's a simple script I use to compile REBOL/flash source files, and then view the compiled results in the browser:

REBOL [title: "Compile and View Flash Files"]

my-rswf-folder: %./
; my-rswf-folder: %/C/12-2-09/My_Docs/WORK/rswf/  ; choose your own
change-dir my-rswf-folder
do %rswf.r   ; assuming you've already saved it to your hard drive
make-swf/save/html to-file request-file/filter "*.rswf"
browse to-file request-file/filter "*.html"

Go ahead and try it now - use the above script to compile the source files downloaded earlier. The compile-run process is unbelievably simple! This next script is a build tool that helps to automate the process of creating, editing, and compil