DO_LOOP, EXIT_LOOP, END_LOOP action


Function
The actions allows to implement a loop.
Declaration
[FOR _ctrlVar [RANGE struct | = lBoundExpr TO uBoundExpr] ] DO_LOOP
 
 ...; actions 1
 
 [EXIT_LOOP [expression]]
 
 ...; actions 2
 
 [EXIT_LOOP [expression]]
 
 ...; akctions 3
 
 END_LOOP

Parameters
expression in Expression of Boolean type.

Description
The loop has two variants:
  1. Loop with using a control variable. At the beginning of the loop, the control variable is set to the value 1 in case of the variant with using the RANGE keyword, or it is set to the value given by the expression lBoundExpr. Value of the expression must be valid. High limit for the value of the control variable is evaluated once, too. In the first case (RANGE), the high limit is the size of given structure (struct\DIM). In the second case, the high limit is acquired by evaluation of the expression uBoundExpr. Value of the expression must be valid. During individual iterations, the control variable of the loop will be increased in successive steps up to the high limit. The control variable must be defined as INT type. It can be changed in the loop body. Possible invalidation of its value will causes an error when executing the END_LOOP action. The loop can be aborted by the EXIT_LOOP action.
    After terminating the cycle, the value of the control variable is the value of the high limit increased by 1.

    INT _i
     INT _uBound
     _uBound := 10
     
     FOR _i=2 TO _uBound DO_LOOP
      _uBound := _uBound + 1 ; value change has no effect on the number of iterations
    
     END_LOOP
     ; value of the variable _i is 11

    INT _i
     RECORD (SD.ArchVal) _struct
     
     REDIM _struct[10]
     
    FOR _i RANGE _struct DO_LOOP
       REDIM _struct[2] ; value change has no effect on the number of iterations
     END_LOOP
     ; value of the variable _i is 11
    
  2. Loop with using no control variable. Actions enclosed between the actions DO_LOOP a END_LOOP will be cyclically executed. The action EXIT_LOOP may terminate a cycle. If the action is with a parameter, then the loop will be terminated when the expression will get the value @TRUE.

     INT _i
     _i := 1
     DO_LOOP
       EXIT_LOOP _i = 10
       _i := _i + 1
     END_LOOP

    Equivalent declaration with no conditional termination of the loop:

     INT _i
     _i := 1DO_LOOP
     
       IF _i = 10 THEN
         EXIT_LOOP
       ENDIF
       _i := _i + 1 END_LOOP

Note
Invalid notation of a loop occurs, if its beginning and end is ''crossed'' with the action IF THEN.

For example:


 
INT _i
 _i := 1

  IF Sec = 1 THEN
   DO_LOOP
 ENDIF
   EXIT_LOOP _i = 10
   _i := _i + 1
 END_LOOP

 
or
 
INT _i
 
 _i := 1
 DO_LOOP
   IF _i = 10 THEN
     EXIT_LOOP
   ENDIF
   _i := _i + 1
 IF Sec = 1 THEN
     _i := _i + 1
   END_LOOP
 ELSE
   END_LOOP
 ENDIF


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