IBM SC34-5764-01 - Manual (Page 90)

Exercise - Writing a Function
Write a function named AVG that receives a list of numbers separated by blanks and computes their
average. The final answer can be a decimal number. To call this function, you would use:
AVG(number1 number2 number3...)
Use the WORDS (see section “WORDS” on page 198) and WORD (see section “WORD” on page 197)
built-in functions.
ANSWER
/*************************** REXX ************************************/
/*
This internal subroutine checks for valid input of "HEADS", */
/* "TAILS", or "" (to quit). If the input is anything else, the */
/* subroutine says the input is not valid and gets the next input. */
/* The subroutine keeps repeating until the input is valid. */
/* Commonly used variables return information to the main program */
/*********************************************************************/
check:
DO UNTIL outcome = 'correct'
SELECT
WHEN flip = 'HEADS' THEN
outcome = 'correct'
WHEN flip = 'TAILS' THEN
outcome = 'correct'
WHEN flip = '' THEN
EXIT
OTHERWISE
outcome = 'incorrect'
PULL flip
END
END
RETURN
Figure 42. Possible Solution (Internal Subroutine Named CHECK)
/******************************* REXX ********************************/
/*
This external subroutine receives the valid input, analyzes it, */
/* gets a random "flip" from the computer, and compares the two. */
/* If they are the same, the user wins. If they are different, */
/* the computer wins. The routine returns the outcome to the */
/* calling program. */
/*********************************************************************/
throw:
ARG input
IF input = 'HEADS' THEN
userthrow = 0 /* heads = 0 */
ELSE
userthrow = 1 /* tails = 1 */
compthrow = RANDOM(0,1) /* choose a random number */
/* between 0 and 1 */
IF compthrow = userthrow THEN
outcome = 'human' /* user chose correctly */
ELSE
outcome = 'machine' /* user chose incorrectly */
RETURN outcome
Figure 43. Possible Solution (External Subroutine named THROW)
Writing Subroutines and Functions
68 CICS TS for VSE/ESA: REXX Guide