IBM TSO/E REXX User Manual

Example of Passing Information in a Variable
/****************************** REXX *******************************/
/* This exec receives a calculated value from an internal */
/* function and displays that value. */
/*******************************************************************/
number1 = 5
number2 = 10
SAY add() /* Displays 15 */
SAY answer /* Also displays 15 */
EXIT
add:
answer = number1 + number2
RETURN answer
Using the same variables in an exec and its internal function can sometimes create
problems. In the following example, the main part of the exec and the function use
the same control variable, "i", for their DO loops. As a result, the DO loop repeats
only once in the main exec because the function returns to the main exec with i =
6.
Example of a Problem Caused by Passing Information in a Variable
/****************************** REXX *******************************/
/* This exec uses an instruction in a DO loop to call an internal */
/* function. A problem occurs because the function also uses a DO */
/* loop with the same control variable as the main exec. The DO */
/* loop in the main exec repeats only once. */
/*******************************************************************/
number1 = 5
number2 = 10
DOi=1TO5
SAY add() /* Displays 105 */
END
EXIT
add:
DOi=1TO5
answer = number1 + number2
number1 = number2
number2 = answer
END
RETURN answer
To avoid this kind of problem in an internal function, you can use:
v The PROCEDURE instruction as described in the next topic.
v Different variable names in a function.
Protecting Variables with the PROCEDURE Instruction: When you use the
PROCEDURE instruction immediately following the function label, all variables used
in the function become local to the function and are shielded from the main part of
the exec. You can also use the PROCEDURE EXPOSE instruction to protect all but
a few specified variables.
Writing a Function
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z/OS V1R1.0 TSO/E REXX User’s Guide

IBM TSO/E REXX Specifications

General

Brand	IBM
Model	TSO/E REXX
Category	Computer Hardware
Language	English

Summary

Part 1. Learning the REXX Language

Chapter 1. Introduction

Explains the REXX programming language, its features, and suitability for various users.

Chapter 2. Writing and Running a REXX Exec

Details the process of writing, running, and understanding REXX execs, including syntax rules and common issues.

Chapter 3. Using Variables and Expressions

Covers REXX variables, expressions, operators, and tracing techniques for data manipulation and calculations.

Chapter 4. Controlling the Flow Within an Exec

Explains how to alter REXX exec execution using conditional, looping, and interrupt instructions.

Chapter 5. Using Functions

Describes REXX functions, including built-in, user-written, and packages, and how to use them.

Chapter 6. Writing Subroutines and Functions

Guides on writing, calling, and passing information to REXX subroutines and functions.

Chapter 7. Manipulating Data

Covers REXX data manipulation using compound variables, stems, and various parsing techniques.

Part 2. Using REXX

Chapter 8. Entering Commands from an Exec

Explains how REXX execs can interact with the operating system by issuing TSO/E and host commands.

Chapter 9. Diagnosing Problems Within an Exec

Details techniques for diagnosing and debugging REXX execs using tracing and special variables.

Chapter 10. Using TSO/E External Functions

Describes TSO/E external functions available for interacting with the system and performing specific tasks.

Chapter 11. Storing Information in the Data Stack

Explains how to use the REXX data stack for temporary storage, passing information, and managing buffers.

Chapter 12. Processing Data and Input/Output Processing

Covers dynamic REXX expression modification and processing data to/from data sets using EXECIO.

Chapter 13. Using REXX in TSO/E and Other MVS Address Spaces

Explains how to run REXX execs in TSO/E and non-TSO/E MVS address spaces and available services.

Part 3. Appendixes

Appendix A. Allocating Data Sets

Guides on creating and allocating data sets, including checklists for ISPF/PDF and ALLOCATE commands.

Appendix B. Specifying Alternate Libraries with the ALTLIB Command

Details using the ALTLIB command to specify and manage alternative libraries for implicit execution.

Appendix C. Comparisons Between CLIST and REXX

Compares REXX and CLIST languages, highlighting similarities and differences in features and capabilities.

Appendix D. Notices

Provides legal notices, warranty disclaimers, copyright, and trademark information.

Bibliography

TSO/E Publications

Lists IBM publications related to TSO/E, including administration, CLISTs, and general information.

Related Publications

Lists IBM publications related to z/OS MVS and ISPF, covering system programming and administration.

Index