Open Object Rexx™

Programming Guide

Version 3.2.0 Edition

Revision 0

October 25, 2007

W. David Ashley
Rony G. Flatscher
Mark Hessling
Rick McGuire
Mark Miesfeld
Lee Peedin
Table of Contents
1. About This Book
Who Should Read This Book
What You Should Know before Reading This Book
Related Information
A Note About Program Examples in this Document
Getting Help
The Rexx Language Association Mailing List
The Open Object Rexx SourceForge Site
comp.lang.rexx Newsgroup
2. Meet Object Rexx
The Main Attractions
Object-Oriented Programming
An English-Like Language
Cross-Platform Versatility
Fewer Rules
Interpreted, Not Compiled
Built-In Functions and Methods
Typeless Variables
String Handling
Clear Error Messages and Powerful Debugging
Impressive Development Tools
Rexx and the Operating System
A Classic Language Gets Classier
From Traditional Rexx to Object Rexx
The Object Advantage
The Next Step
3. A Quick Tour of Traditional Rexx
What Is a Rexx Program?
Running a Rexx Program
Elements of Rexx
Writing Your Program
Testing Your Program
Improving Startup Time
Variables, Constants, and Literal Strings
Assignments
Using Functions
Program Control
Subroutines and Procedures
4. Into the Object World
What Is Object-Oriented Programming?
Modularizing Data
Modeling Objects
How Objects Interact
Methods
Polymorphism
Classes and Instances
Data Abstraction
Subclasses, Superclasses, and Inheritance
5. The Basics of Classes
Rexx Classes for Programming
The Alarm Class
The Collection Classes
The Message Class
The Monitor Class
The Stem Class
The Stream Class
The String Class
The Supplier Class
Rexx Classes for Organizing Objects
The Object Class
The Class Class
Rexx Classes: The Big Picture
Creating Your Own Classes Using Directives
What Are Directives?
The Directives Rexx Provides
How Directives Are Processed
A Sample Program Using Directives
Another Sample Program
Creating Classes Using Messages
Defining a New Class
Adding a Method to a Class
Defining a Subclass of the New Class
Defining an Instance
Types of Classes
Object Classes
Abstract Classes
Mixin Classes
Metaclasses
6. A Closer Look at Objects
Using Objects in Rexx Clauses
Common Methods
Initializing Instances Using INIT
Returning String Data Using STRING
Uninitializing and Deleting Instances Using UNINIT
Special Variables
Public, Local, and Built-In Environment Objects
The Public Environment Object (.environment)
The Local Environment Object (.local)
Built-In Environment Objects
The Default Search Order for Environment Objects
Determining the Scope of Methods and Variables
Objects with a Class Scope
Objects with Their Own Unique Scope
More about Methods
The Default Search Order for Selecting a Method
Changing the Search Order for Methods
Public versus Private Methods
Defining an UNKNOWN Method
Concurrency
Inter-Object Concurrency
Intra-Object Concurrency
7. Commands
How to Issue Commands
Command Echo
Rexx and Batch Files
Issuing a Command to Call a .CMD File
Using Variables to Build Commands
Using Quotation Marks
ADDRESS Instruction
Using Return Codes from Commands
Subcommand Processing
Trapping Command Errors
Instructions and Conditions
Disabling Traps
Using SIGNAL ON ERROR
Using CALL ON ERROR
A Common Error-Handling Routine
8. Input and Output
More about Stream Objects
Reading a Text File
Reading a Text File into an Array
Reading Specific Lines of a Text File
Writing a Text File
Reading Binary Files
Reading Text Files a Character at a Time
Writing Binary Files
Closing Files
Direct File Access
Checking for the Existence of a File
Getting Other Information about a File
Using Standard I/O
Using Windows Devices
A. Rexx Application Programming Interfaces
Handler Characteristics
RXSTRINGs
Calling the Rexx Interpreter
From the Operating System
From within an Application
The RexxStart Function
The RexxWaitForTermination Function
The RexxDidRexxTerminate Function
Subcommand Interface
Registering Subcommand Handlers
Subcommand Interface Functions
External Function Interface
Registering External Functions
Calling External Functions
External Function Interface Functions
System Exit Interface
Writing System Exit Handlers
System Exit Definitions
System Exit Interface Functions
Variable Pool Interface
Interface Types
RexxVariablePool Restrictions
RexxVariablePool Interface Function
Dynamically Allocating and De-allocating Memory
The RexxAllocateMemory() Function
The RexxFreeMemory() Function
Queue Interface
Queue Interface Functions
Halt and Trace Interface
Halt and Trace Interface Functions
Macrospace Interface
Search Order
Storage of Macrospace Libraries
Macrospace Interface Functions
Windows Scripting Host Interface
Concurrency
WSH Features
B. Distributing Programs without Source
C. Sample Rexx Programs
D. Notices
Trademarks
Source Code For This Document
E. Common Public License Version 1.0
Definitions
Grant of Rights
Requirements
Commercial Distribution
No Warranty
Disclaimer of Liability
General
Index
List of Figures
2-1. Objects in a Billing Application
4-1. Modular Data--a Report Object
4-2. A Ball Object
4-3. Ball Object with Variable Names and Values
4-4. Encapsulated 5 Object
4-5. A Simple Class
4-6. Icon Class
4-7. Instances of the Icon Class
4-8. Superclass and Subclasses
4-9. The Screen-Object Superclass
4-10. Multiple Inheritance
5-1. How Subclasses Inherit Instance Methods from the Class Class
5-2. Classes and Inheritance (part 1 of 7)
5-3. Classes and Inheritance (part 2 of 7)
5-4. Classes and Inheritance (part 3 of 7)
5-5. Classes and Inheritance (part 4 of 7)
5-6. Classes and Inheritance (part 5 of 7)
5-7. Classes and Inheritance (part 6 of 7)
5-8. Classes and Inheritance (part 7 of 7)
6-1. Instance Methods and Class Methods
6-2. Instances in the Part Class
6-3. Scope of the Number Class
6-4. Searching the Hierarchy for a Method
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