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Breaking Out of While Loops
Use the endloop statement to break out of a while loop. Endloop immediately closes the loop, and execution continues with the first statement following endwhile. For example:
while condition1 do
  statementlist1
  if condition2 then
    endloop; 
  endif;
  statementlist2
endwhile;
If condition2 is true, statementlist2 is not executed in that pass through the loop, and the entire loop is closed.
You can use nested while statements in 4GL, and you can control breaking out of nested loops by using labels, which allow the endloop statement to break to a specific level.
For example:
label1: while condition1 do 
  statementlist1 
  label2: while condition2 do
    statementlist2
    if condition3 then
      endloop label1;
    elseif condition4 then 
      endloop label2;
    endif;
    statementlist3
  endwhile;
  statementlist4
endwhile;
There are two possible breaks out of the inner loop. If condition3 is true, endloop closes both loops, and control resumes at the statement following the outer loop. If condition4 is true, only the inner loop closes, and execution continues at the beginning of statementlist4.
If you do not specify a label after endloop, only the innermost loop currently active is closed. See the section on endloop in this chapter for additional information.
Examples
Repeat a prompt five times or until a valid answer is given:
answer := ' '; 
requests := 0; 
while (lowercase(left(answer,1)) != 'y' and
  lowercase(left(answer,1)) != 'n' and 
  requests < 5) do 
  answer := prompt 'Please answer Y or N:'; 
  requests := requests + 1; 
endwhile;
Use the while statement to handle deadlock:
succeed := 0;   /* Set to 1 when and if */
                /* insert is successful */
tries := 1;
ingerr := 0;

A:  while succeed = 0 and tries <= 10 do
    insert statement to try to insert
    into database
        inquire_sql (ingerr = dbmserror);
        if ingerr = 0 then
      /* Insert completed successfully -  */
      /* commit the change           */

      commit;
      succeed := 1;
    elseif ingerr=4700 then
      /* Error due to deadlock - try again */
      tries := tries + 1;
    else
      endloop A;
    endif;
  endwhile;
if succeed = 1 then
  message 'Insert completed successfully';
  sleep 3;
else
  message 'Insert failed';
  sleep 3;
endif;
Last modified date: 08/28/2024