While: what changed

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Title: While

New		Line
1	+	`while` in conjunction with [[Do\|do]] repeats a statement as long as a condition evaluates to [[True\|true]]. The condition [[expression]] is evaluated prior each iteration, determining whether the following [[statement]] is executed. This is the main difference to a [[Repeat\|repeat … until-loop]], where the [[Loops\|loop]] body is executed at any rate, but succeeding iterations do not necessarily happen, though.
2	+
3	+	The following example contains unreachable code:
4	+
5	+	``` pascal
6	+	program whileFalse(input, output, stderr);
7	+
8	+	begin
9	+	while false do
10	+	begin
11	+	writeLn('never gets printed');
12	+	end;
13	+	end.
14	+	```
15	+
16	+	You usually use `while`-loops where, in contrast to [[For\|for-loops]], a running index [[Variable\|variable]] is not required, the statement executed can't be deduced from an index that's incremented by one, or to avoid a [[Break\|break-statement]] (which usually indicates bad programming style).
17	+
18	+	``` pascal
19	+	program whileDemo(input, output, stderr);
20	+
21	+	var
22	+	x: integer;
23	+	begin
24	+	x := 1;
25	+
26	+	// prints non-negative integer powers of two
27	+	while x < high(x) div 2 do
28	+	begin
29	+	writeLn(x);
30	+	inc(x, x); // x := x + x
31	+	end;
32	+	end.
33	+	```
34	+
35	+	## see also
36	+
37	+	- [[Infinite loop]]
38	+
39	+	---
40	+	From the Free Pascal wiki, page "While", as it stood on 2023-01-25 after a change by Kai Burghardt, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).
41	+	Category: Code

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