Loops
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A loop control structure repeats a statement as long as a certain condition is met.
properties
A loop is sectioned into a
- loop head, and a
- loop body.
The loop body is a statement, and the head contains a Boolean expression that determines whether the loop body is executed (again).
Loops are particularly useful as a programming construct, since the loop body is only inserted once in the final program. The so-called “loop unrolling” optimization may copy the loop body multiple times anyway, but still you do not need to literally repeat the statements in your source code.
types
Pascal defines
- counting loops
for … to|downto do
- conditional loops
while … do
, andrepeat … until
where the loop head appears at the foot.
The FPC also supports for … in … do
loops.
comparative remark
Unlike in some programming languages, in Pascal a loop itself is a statement; it does not yield a value. Also, a loop body does not create a new scope.