IBM TSO/E REXX User Manual

The logical operators are:
Operator Meaning
& AND
Returns 1 if both comparisons are true. For example:
(4 > 2) & (a = a) /* true, so result is 1 */
(2 > 4) & (a = a) /* false, so result is 0 */
| Inclusive OR
Returns 1 if at least one comparison is true. For example:
(4 > 2) | (5 = 3) /* at least one is true, so result is 1 */
(2 > 4) | (5 = 3) /* neither one is true, so result is 0 */
&& Exclusive OR
Returns 1 if only one comparison (but not both) is true. For
example:
(4 > 2) && (5 = 3) /* only one is true, so result is 1 */
(4 > 2) && (5 = 5) /* both are true, so result is 0 */
(2 > 4) && (5 = 3) /* neither one is true, so result is 0 */
Prefix \ Logical NOT
Returns the opposite response. For example:
\ 0 /* opposite of 0, so result is 1 */
\ (4 > 2) /* opposite of true, so result is 0 */
Using Logical Expressions
Logical expressions are used in complex conditional instructions and can act as
checkpoints to screen unwanted conditions. When you have a series of logical
expressions, for clarification, use one or more sets of parentheses to enclose each
expression.
IF ((A < B) | (J < D)) & ((M = Q) | (M = D)) THEN ...
The following example uses logical operators to make a decision.
Example Using Logical Expressions
/***************************** REXX ********************************/
/* This exec receives arguments for a complex logical expression */
/* that determines whether a person should go skiing. The first */
/* argument is a season and the other two can be 'yes' or 'no'. */
/*******************************************************************/
PARSE ARG season snowing broken_leg
IF ((season = 'winter') | (snowing ='yes')) & (broken_leg ='no')
THEN SAY 'Go skiing.'
ELSE
SAY 'Stay home.'
When arguments passed to this example are "spring yes no", the IF clause
translates as follows:
Using Expressions
Chapter 3. Using Variables and Expressions 33

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