Difference between revisions of "Loops"
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| − | A loop | + | A '''loop''' control structure repeats a [[statement]] as long as a certain condition is met. |
| − | A loop | + | == 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 Expressions|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 | + | 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|source code]]. |
| − | + | == types == | |
| + | [[Standard Pascal|Pascal]] defines | ||
| + | * counting loops [[For|<syntaxhighlight lang="pascal" inline>for … to|downto do</syntaxhighlight>]] | ||
| + | * conditional loops | ||
| + | ** [[While|<syntaxhighlight lang="pascal" inline>while … do</syntaxhighlight>]], and | ||
| + | ** [[Repeat|<syntaxhighlight lang="pascal" inline>repeat … until</syntaxhighlight>]] where the loop head appears at the foot. | ||
| − | + | The [[FPC]] also supports [[for-in loop|<syntaxhighlight lang="pascal" inline>for … in … do</syntaxhighlight>]] 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|scope]]. | ||
| + | == see also == | ||
* [[Pascal basics]] | * [[Pascal basics]] | ||
| − | + | * [[Main Loop Hooks]] | |
[[Category:Pascal]] | [[Category:Pascal]] | ||
[[Category:Control Structures]] | [[Category:Control Structures]] | ||
Revision as of 20:48, 20 August 2020
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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 … untilwhere 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.
