IBM SC34-5764-01, Manual

Page: 121 / 481

Congratulations! Now you know the best ways to program your REXX execs. Have fun writing programs
that will make your life easier!
/********************************************************/
/* SAMPLE #3:
A portion of CATMOUSE EXEC */
/* divided into segments and written with 'more' */
/* indentation and 'more' comments. */
/* Note commands in uppercase (to highlight logic) */
/********************************************************/
/********************************************************/
/* Main program
*/
/********************************************************/
DO FOREVER
CALL display
/**********************************/
/* Mouse's turn
*/
/**********************************/
PULL move
IF datatype(move,whole) & move >= 0 & move <=2
THEN SELECT
WHEN mouse+move > len /* mouse hits wall */
THEN nop /* and loses turn */
WHEN cat > mouse,
& mouse+move >= cat, /* mouse hits cat */
THEN mouse = cat /* and loses game */
OTHERWISE mouse = mouse + move /* mouse ... */
END /* moves to new location */
IF mouse = hole THEN LEAVE /* mouse is home safely */
IF mouse = cat THEN LEAVE /* mouse hits cat (ouch) */
/**********************************/
/* Cat's turn
*/
/**********************************/
jump = RANDOM(1,spring)
/* determine cat's move */
IF cat > mouse /* cat must jump left */
THEN DO
IF cat-jump < 1 /* cat hits wall */
THEN nop /* misses turn */
ELSE cat = cat-jump /* cat jumps left */
END
ELSE DO /* cat must jump right */
IF cat+jump > len /* cat hits wall */
THEN nop /* misses turn */
ELSE cat = cat+jump /* cat jumps right */
END
IF cat = mouse THEN LEAVE /* cat catches mouse */
END
/********************************************************/
/* Conclusion
*/
/********************************************************/
CALL display
/* on final display */
IF cat = mouse /* who won? */
THEN say "Cat wins" /* ... the cat */
ELSE say "Mouse wins" /* ... the mouse */
EXIT
Programming Style and Techniques
Chapter 10. Programming Style and Techniques
99