Filter
Top Products
Chapter 5. Using Functions
This chapter defines what a function is and describes how to use the built-in functions.
What is a Function?
A function is a sequence of instructions that can receive data, process it, and return a value. In REXX,
there are several kinds of functions:
v Built-in functions are built into the language processor. More about built-in functions appears later in this
chapter.
v User-written functions are those an individual user writes or an installation supplies. These can be
internal or external. An internal function is part of the current program that starts at a label. An
external function is a self-contained program or program outside the calling program. More information
about user-written functions appears in section “Writing Subroutines and Functions” on page 58.
Regardless of the kind of function, all functions return a value to the program that issued the function call.
To call a function, type the function name immediately followed by parentheses enclosing arguments to the
function (if any). 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. Arguments can be:
v Constant
function(55)
v Symbol
function(symbol_name)
v Option that the function recognizes
function(option)
v Literal string
function('With a literal string')
v Unspecified or omitted
function()
v Another function
function(function(arguments))
v Combination of argument types
function('With literal string', 55, option)
function('With literal string',, option) /* Second argument omitted */
All functions must return values. When the function returns a value, the value replaces the function call. In
the following example, the language processor adds the value the function returns to 7 and produces the
sum.
SAY 7 + function(arguments)
A function call generally appears in an expression. Therefore a function call, like an expression, does not
usually appear in an instruction by itself.
Example of a Function
Calculations that functions represent often require many instructions. For instance, the simple calculation
for finding the highest number in a group of three numbers, might be written as follows:
© Copyright IBM Corp. 1992, 2009 51