Rexx Tutorial on Rexx Subroutines
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in any programming language, the entire program is broken into logical modules. this makes it easier to write code that can be maintained easily. this is a basic requirement for any programming language.

in rexx, modules can be written using subroutines and functions. let’s look at the subroutines in detail.

defining a subroutine

the syntax of a function declaration is as follows −

functionname: 
   statement#1 
   statement#2 
   …. 
   statement#n

where,

  • functionname − this is the name assigned to the subroutine.

  • statement#1 .. statement#n − these are the list of statements that make up the subroutine.

the following program is a simple example showing the use of subroutines.

/* main program */ 
call add 
exit 
add: 
a = 5 
b = 10 
c = a + b 
say c

the following things should be noted about the above program −

  • we are defining a subroutine called add.

  • the subroutine does a simple add functionality.

  • the exit statement has to be used to signify the end of the main program.

the output of the above program would be as follows −

15

working with arguments

it is also possible to work with arguments in rexx. the following example shows how this can be achieved.

/* main program */ 
call add 1,2 
exit 
add: 
parse arg a,b 
c = a + b 
say c

the following things should be noted about the above program −

  • we are defining a subroutine called add which takes on 2 parameters.

  • in the subroutines, the 2 parameters are parsed using the parse and arg keyword.

the output of the above program would be as follows −

3

different methods for arguments

let’s look at some other methods available for arguments.

arg

this method is used to return the number of arguments defined for the subroutine.

syntax −

arg()

parameters − none

return value − this method returns the number of arguments defined for the subroutine.

example −

/* main program */ 
call add 1,2 
exit 
add: 
parse arg a,b 

say arg() 
c = a + b 
say c

when we run the above program we will get the following result.

2 
3

arg(index)

this method is used to return the value of the argument at the specific position.

syntax −

arg(index)

parameters

  • index − index position of the argument to be returned.

return value − this method returns the value of the argument at the specific position.

example −

/* main program */ 
call add 1,2 
exit 
add: 
parse arg a,b 

say arg(1) 
c = a + b 
say c

when we run the above program we will get the following result.

1 
3
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