Postconditionals

Material prepared from M Programming Book [WALTERS1997] (page 107)

When a GOTO or DO depends on a condition (the value of a variable), a postconditional can be used as an argument for these commands:

MENU
 WRITE "What would you like to know about MUMPS?"
 WRITE !?3,"1. What does it stands for?"
 WRITE !?3,"2. When was it created?"
 WRITE !?3,"3. Who created MUMPS?"
 WRITE !?3,"4. I know everything I need already, please quit."
retry READ !,"Answer with a number between 1 and 4: ",ans
 IF ans<1!(ans>4) GOTO retry
 QUIT:ans=4
 DO meaning:ans=1,date:ans=2,creator:ans=3
 GOTO MENU
meaning;
 WRITE !!?3,"MUMPS stands for Massachusetts General Hospital Utility Multi-Programming System.",!!
 QUIT
date;
 WRITE !!?3,"MUMPS was was created between 1966 and 1967.",!!
 QUIT
creator;
 WRITE !!?3,"Neil Pappalardo is MUMPS creator.",!!
 QUIT