A conditional phrase can
modify the iteration of a repetitive loop. It can cause the termination
of a loop. It can follow any of the forms of
repetitor (none, FOREVER,
simple, controlled, OVER, or WITH). If you specify WHILE or UNTIL,
exprw or
expru, respectively, is evaluated after
each loop using the latest values of all variables, and the loop is ended if
exprw evaluates to
0 or
expru evaluates to
1.
For a WHILE loop, the condition is evaluated at the top of the group of
instructions. For an UNTIL loop, the condition is evaluated at the bottom—before
the control variable has been stepped.
