DO Statement with a WHILE Clause

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Language Reference

DO Statement with a WHILE Clause

conditionally executes statements iteratively

DO WHILE( expression);

DO variable=start TO stop <BY increment> WHILE(expression);

The inputs to the DO WHILE statement are as follows:

expression: is an expression that is evaluated at the top of the loop for being true or false.
variable: is the name of a variable indexing the loop.
start: is the starting value for the looping variable.
stop: is the stopping value for the looping variable.
increment: is an increment value.

Using a WHILE expression makes possible the conditional execution of a set of statements iteratively. The WHILE expression is evaluated at the top of the loop, and the statements inside the loop are executed repeatedly as long as the expression yields a nonzero or nonmissing value.

Note that the incrementing is done before the WHILE expression is tested. The following example demonstrates the incremeting:

   x=1;
   do while(x<100);
      x+1;
   end;
   print x;          /* x=100                           */

The next example increments the starting value by 2:

   y=1;
   do x=1 to 100 by 2 while(y<200);
      y=y#x;
   end;              /* at end of loop, x=11 and y=945  */

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