IBM TSO/E REXX User Manual

Chapter 5. Using Functions
What is a Function? .......................61
Example of a Function .....................62
Built-In Functions ........................63
Arithmetic Functions ......................63
Comparison Functions .....................63
Conversion Functions .....................64
Formatting Functions......................64
String Manipulating Functions ..................64
Miscellaneous Functions ....................65
Testing Input with Built-In Functions ................66
Exercise - Writing an Exec with Built-In Functions ..........66
This chapter defines what a function is and describes how to use the built-in
functions.
What is a Function?
Afunction is a sequence of instructions that can receive data, process that data, and
return a value. In REXX, there are several kinds of functions:
v Built-in functions — These functions are built into the language processor. More
about built-in functions appears later in this chapter.
v User-written functions — These functions are written by an individual user or
supplied by an installation and can be internal or external. An internal function is
part of the current exec that starts at a label. An external function is a
self-contained program or exec outside of the calling exec. More information
about user-written functions appears in “Writing a Function” on page 77.
v Function packages — These are groups of functions and subroutines written by
an individual user or supplied by an installation. They are link-edited into load
modules and categorized as user, local, and system. TSO/E external functions
are provided in a system function package. More information about TSO/E
external functions appears in “TSO/E External Functions” on page 119.
Regardless of the kind of function, all functions return a value to the exec that
issued the function call. To call a function, type the function name directly followed
by one or more arguments within parentheses. There can be no space between
the function name and the left parenthesis.
function(arguments)
A function call can contain up to 20 arguments separated by commas. Each
argument can be one or more of the following.
v Blank
function( )
v Constant
function(55)
v Symbol
function(symbol_name)
v Literal string
function('With a literal string')
v Option recognized by the function
© Copyright IBM Corp. 1988, 2001 61

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