;: what changed
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Title: ;
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| 1 | + | ; | |
| 2 | + | ||
| 3 | + | The **semicolon** `;` is used to | |
| 4 | + | ||
| 5 | + | - conclude a [[Declaration|declaration]], | |
| 6 | + | - conclude a constant, `resourceString`, or [[Type|type]] definition, | |
| 7 | + | - separate formal parameters in a routine signature, | |
| 8 | + | - separate a routine declaration from its attributes, | |
| 9 | + | - terminate the program header, | |
| 10 | + | - separate alternatives in variant records, and to | |
| 11 | + | - *separate* statements, in contrast to other programming language where its purpose is to *terminate* a statement. | |
| 12 | + | ||
| 13 | + | ## statement separator | |
| 14 | + | ||
| 15 | + | ### necessity | |
| 16 | + | ||
| 17 | + | Since language constructs only in their entirety constitute statements, semicolons may not split their components. Most notably `;` cannot appear immediately before an [[Else|else]] that is part of an [[If and Then|if … then branch]]. However, `;` in front of an [[End|end]] usually is not necessary, but optional and it does not harm insert one anyway. | |
| 18 | + | ||
| 19 | + | As a demonstration, that a single semicolon can make the difference, consider the following listings: | |
| 20 | + | ||
| 21 | + | ``` pascal | |
| 22 | + | case c of | |
| 23 | + | 0: if false then c := 42; | |
| 24 | + | else c := -1; | |
| 25 | + | end; | |
| 26 | + | ``` | |
| 27 | + | ||
| 28 | + | If `c` is zero, it remains zero, but becomes `-1` otherwise. | |
| 29 | + | ||
| 30 | + | ``` pascal | |
| 31 | + | case c of | |
| 32 | + | 0: if false then c := 42 | |
| 33 | + | else c := -1; | |
| 34 | + | end; | |
| 35 | + | ``` | |
| 36 | + | ||
| 37 | + | Here, `c` only becomes `-1` if it has been zero before. As a consequence, and general advice, always put everything in compound statements (i. e. embrace your statements by [[Begin|begin]] and `end`) where it is allowed, in order to mitigate such issues. | |
| 38 | + | ||
| 39 | + | > **Note:** Using `otherwise` (an [[Extended Pascal]] extension) instead of `else` in `case`-statements may prevent such mistakes. | |
| 40 | + | ||
| 41 | + | ### empty statement | |
| 42 | + | ||
| 43 | + | In a sequence a semicolon without a preceding (qualified) statement indicates an **empty statement**. | |
| 44 | + | ||
| 45 | + | Historically empty statements were used in conjunction with [[Label|labels]]. Originally labels can only defined where a statement exists. If for instance a whole list of statements had to be bypassed, but no qualified statement followed thereafter, the empty statement still provided the possibility. | |
| 46 | + | ||
| 47 | + | Also historically, [[Case|case-statements]] had to list all possible values the selector variable theoretically could have. Now, if a value or range did not imply any action, yet had to be listed inside the `case`-statement in order to fulfill this requirement, an empty statement is the shortest possible way to implement the situation. | |
| 48 | + | ||
| 49 | + | ## other remarks | |
| 50 | + | ||
| 51 | + | In the [[ASCII]] character set the semicolon takes the value `59` ([[Hexadecimal|hexadecimal]] `$3B`). | |
| 52 | + | ||
| 53 | + | --- | |
| 54 | + | *From the Free Pascal wiki, page ";", as it stood on 2021-07-04 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).* |