WHILE

The WHILE statement is used in conjunction with the FOR / NEXT or LOOP / REPEAT constructs to determine whether execution of the loop should continue.

Format

WHILE expr

where

The WHILE statement causes execution of the innermost FOR/NEXT or LOOP/REPEAT construct to terminate if the value of expr is False. It is equivalent to a statement such as

IF expr = 0 THEN EXIT

If the CONDITIONAL.STATEMENTS option of the $MODE compiler directive is active, expr may be one of the following statements that in its normal form has a THEN/ELSE clause:

FILELOCK, FILEUNLOCK, FIND, FINDSTR, FLUSH, GETLIST, LOCATE, MATREAD, MATREADCSV, MATREADL, MATREADU, OPEN, OPENPATH, OPENSEQ, OSREAD, READ, READBLK, READCSV, READL, READLIST, READNEXT, READSEQ, READU, READV, READVL, READVU, SEEK, WRITEBLK, WRITECSV, WRITESEQ

When used in this way, the LOCKED or ON ERROR clauses normally associated with some of these statements are not available.

Examples

LOOP

  REMOVE ITEM FROM LIST SETTING DELIMITER

  DISPLAY ITEM

WHILE DELIMITER

REPEAT

This program fragment displays items removed from dynamic array LIST. The loop is terminated when the value of DELIMITER becomes zero.

SELECT FV

LOOP

WHILE READNEXT ID

  ...processsing...

REPEAT

The above program fragment, which requires the CONDITIONAL.STATEMENTS option of the $MODE compiler directive to be active, uses the READNEXT statement as a conditional element in the loop.

See also:

EXIT, UNTIL