Colon: what changed
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Title: Colon
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| 1 | + | <div style="float:right; margin: 0 25px 20px 0; padding:50px; font-size:500%; font-family: Georgia; background-color: #f9f9f9; border: 2px solid #777777;"> | |
| 2 | + | ||
| 3 | + | ||
| 4 | + | </div> | |
| 5 | + | ||
| 6 | + | The symbol `:`, pronounced “colon”, is used in [[Pascal]] in several ways: | |
| 7 | + | ||
| 8 | + | - in an [[Identifier|identifier]] declaration it separates the [[Type|type]] | |
| 9 | + | - most notably in [[Var|var]] sections | |
| 10 | + | - but also in [[Const|const]] sections (in case of *explicitely* typed constants) | |
| 11 | + | - [[Procedure|procedure]] and [[Function|function]] parameters have a type, too | |
| 12 | + | - and return values of functions (including operator overloads) | |
| 13 | + | - as well as [[Property|properties]] | |
| 14 | + | - in general, everywhere where a new identifier associated with some memory, is introduced (also custom structured type definitions) | |
| 15 | + | - in [[Case|case]] selectors it closes a match-list | |
| 16 | + | - in [[Label|label]] definitions the colon seperates the instruction from the label name | |
| 17 | + | - also some routines, especially the [[Str]], [[Write|write]] and `writeLn` procedures accept further parameters via colon separated arguments | |
| 18 | + | - Offset / segment separation under DOS `Mem[$B800:$0000]` | |
| 19 | + | ||
| 20 | + | The following example shows the most prevalent usage scenarios: | |
| 21 | + | ||
| 22 | + | ``` pascal | |
| 23 | + | program colonDemo(input, output, stderr); | |
| 24 | + | ||
| 25 | + | procedure numberReport(const i: int64); | |
| 26 | + | begin | |
| 27 | + | case i of | |
| 28 | + | low(i)..-1: | |
| 29 | + | begin | |
| 30 | + | writeLn('Your number is negative. ☹'); | |
| 31 | + | end; | |
| 32 | + | 1..high(i): | |
| 33 | + | begin | |
| 34 | + | // right aligns to a width of 24 characters | |
| 35 | + | writeLn(i:24); | |
| 36 | + | end; | |
| 37 | + | else | |
| 38 | + | begin | |
| 39 | + | writeLn('You''ve entered zero.'); | |
| 40 | + | end; | |
| 41 | + | end; | |
| 42 | + | end; | |
| 43 | + | ||
| 44 | + | var | |
| 45 | + | i: int64; | |
| 46 | + | ||
| 47 | + | begin | |
| 48 | + | writeLn('Enter a number:'); | |
| 49 | + | readLn(i); | |
| 50 | + | numberReport(i); | |
| 51 | + | end. | |
| 52 | + | ``` | |
| 53 | + | ||
| 54 | + | ## other remarks | |
| 55 | + | ||
| 56 | + | - Colon appears in the assignment operator [[Becomes|:=]]. | |
| 57 | + | - In [[ASCII]] the character colon `:` has the value `58`. | |
| 58 | + | ||
| 59 | + | --- | |
| 60 | + | *From the Free Pascal wiki, page "Colon", as it stood on 2022-08-06 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).* | |
| 61 | + | Category: Code |