"C" wish list.

[cjl at iuvax.UUCP]

  I would like to see a loop-exit statement added to replace the break 
statement.  For example a loop with multi-exit points should not pretend
to be a "for" loop like :

    for (i=0; i<100; i++) {
      /* IN NATURAL LANG, THIS MEANS THE LOOP HAS A SIMPLE EXIT POINT,
      -- AND WILL ITERATE EXACTLY 100 TIMES. */
        checkReturn = function1(x);

	if (checkReturn == BAD) break;
          /* THE BREAK STATEMENT HERE FUNCTIONS LIKE GOTO AND DESTROYS
          -- THE ORIGINAL, SIMPLE MEANING OF FOR STATEMENT.     */
        ......
	checkReturn = function5(x);
	if (checkReturn == BAD)
	    result[i] = 0;
	else
	    result[i] = function6(x);
     }

 With loop-exit statement, the reader is warned explicitly the
existence of multi-exit ( or break) points inside the loop.

      i = 0;
      loop {
        /* WHENEVER WE SEE A LOOP STATEMENT, WE KNOW THERE MAY HAVE
        -- SEVERAL EXIT POINTS. IT IS NOT AN EASY LOOP. */ 

        if  (i>=100) then exit;
        /* NOW YOU DON'T HAVE THE IMPRESSION THAT THE LOOP 
        -- WILL ALWAYS ITERATE 100 TIMES BECAUSE THERE MAY EXIST
        -- OTHER EXIT POINTS. */ 

        checkReturn = function1(x); 
        if (checkReturn == BAD) exit; 
        .................  
        checkReturn = function5(x);
	if (checkReturn == BAD)
	    result[i] = 0;
	else
	    result[i] = function6(x);
        i++;
      }

This is a style encouraged by Ada or Modula-2 language.
In existing C language, we may use macro definitions to simulate 
the loop-exit statement as :

define loop for(,,)
define exit break

C.J.Lo
Dept. of CIS, IUPUI
ARPA : cjl at Indiana@CSNet-Relay
UUCP : ...!iuvax!cjl