Repeat: what changed

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Title: Repeat

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1	+	This [[Reserved word\|reserved words]] `repeat` in conjunction with `until` are used to create tail-controlled [[Loops\|loops]].
2	+
3	+	## syntax
4	+
5	+	A tail-controlled loops start with `repeat`, followed by a possibly empty list of [[statement\|statements]], and concluded by `until` and a `Boolean` [[expression]].
6	+
7	+	The following ([[Infinite loop\|infinite]]) loops demonstrate the syntax:
8	+
9	+	``` pascal
10	+	// empty loop body is legal:
11	+	repeat
12	+	until false;
13	+	```
14	+
15	+	Note, `repeat` and `until` already form a frame in their own right. You do not need to surround your statements by an extra [[Begin\|begin]] … [[End\|end]]-frame. In fact, you can put as many sequences (also called compound statements) between `repeat` and `until` as you want:
16	+
17	+	``` pascal
18	+	repeat
19	+	begin
20	+	write('x');
21	+	end;
22	+	begin
23	+	write('o');
24	+	end;
25	+	until false;
26	+	```
27	+
28	+	Note, it is not necessary, but allowed to put a [[;\|semicolon]] prior `until`:
29	+
30	+	``` pascal
31	+	repeat
32	+	write('zZ')
33	+	until false;
34	+	```
35	+
36	+	## semantics
37	+
38	+	Since the loop “head” appears at the tail, the loop body is executed at least once and the loop condition evaluated at the end of every iteration. If the condition evaluates to [[false and true\|false]], another iteration occurs.
39	+
40	+	Therefore, `repeat` … `until` loops are particularly useful to ensure a certain sequence of statements is run at least once.
41	+
42	+	``` pascal
43	+	repeat
44	+	write('Enter a positive number: ');
45	+	readLn(i);
46	+
47	+	// readLn loads a default value if the source is EOF.
48	+	// For integer values the default is zero.
49	+	// Since our loop condition requires _positive_ values,
50	+	// this loop would be stuck _indefinitely_ if EOF(input).
51	+	// Ergo, we check for that:
52	+	if eof(input) then
53	+	begin
54	+	writeLn;
55	+	writeLn(stdErr, 'error: input has reached EOF');
56	+	halt(1);
57	+	end;
58	+	until i > 0;
59	+	```
60	+
61	+	The user will be prompted again and again, but at least once, until he finally enters a positive number.
62	+
63	+	Another standard usage example is the reverse Horner scheme as demonstrated in [[Base converting]].
64	+
65	+	## see also
66	+
67	+	- [[While\|while]] for head-controlled loops
68	+	- [[Break\|break]]
69	+	- [[Continue\|continue]]
70	+	- Object Pascal Tutorial on [[Basic Pascal Tutorial/Chapter 3/REPEAT..UNTIL\|repeat…until]]
71	+
72	+	---
73	+	From the Free Pascal wiki, page "Repeat", 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).
74	+	Category: Code

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