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DO outer=1TO2
DO inner=1TO2
SAY 'HIP'
END
SAY 'HURRAH'
END
The output from this example is:
HIP
HIP
HURRAH
HIP
HIP
HURRAH
If you need to leave a loop when a certain condition arises, use the LEAVE instruction followed by the
name of the control variable of the loop. If the LEAVE instruction is for the inner loop, processing leaves
the inner loop and goes to the outer loop. If the LEAVE instruction is for the outer loop, processing leaves
both loops.
To leave the inner loop in the preceding example, add an IF...THEN...ELSE instruction that includes a
LEAVE instruction after the IF instruction.
DO outer=1TO2
DO inner=1TO2
IF inner > 1 THEN
LEAVE inner
ELSE
SAY 'HIP'
END
SAY 'HURRAH'
END
The result is as follows:
HIP
HURRAH
HIP
HURRAH
Exercises - Combining Loops
1. What happens when the following program runs?
DO outer=1TO3
SAY /* Produces a blank line */
DO inner=1TO3
SAY 'Outer' outer 'Inner' inner
END
END
2. Now what happens when the LEAVE instruction is added?
DO outer=1TO3
SAY /* Produces a blank line */
DO inner=1TO3
IF inner = 2 THEN
LEAVE inner
ELSE
SAY 'Outer' outer 'Inner' inner
END
END
ANSWERS
1. When this example runs, it produces the following:
Control Flow within a Program
Chapter 4. Controlling the Flow within a program 47