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, and
  • repeat … 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.

see also

• Pascal basics
• Main Loop Hooks