$IF: what changed
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Title: $IF
| Old | New | Line | |
|---|---|---|---|
| 1 | + | The | |
| 2 | + | ||
| 3 | + | ``` pascal | |
| 4 | + | {$if …} | |
| 5 | + | ``` | |
| 6 | + | ||
| 7 | + | directive can be used in [[Conditional compilation|conditional compilation]]. | |
| 8 | + | ||
| 9 | + | ``` pascal | |
| 10 | + | // pointermath directive did not exist prior FPC 3.0.0 | |
| 11 | + | {$if FPC_VERSION > 2} | |
| 12 | + | // pointer arithmetics is bad. very bad | |
| 13 | + | {$pointermath off} | |
| 14 | + | {$endif} | |
| 15 | + | ``` | |
| 16 | + | ||
| 17 | + | Also, enable you to write complex conditions that you cannot do with the | |
| 18 | + | ||
| 19 | + | ``` pascal | |
| 20 | + | {$ifdef …} | |
| 21 | + | ``` | |
| 22 | + | ||
| 23 | + | , | |
| 24 | + | ||
| 25 | + | And there are two bool functions\[defined/undefined\] that can be mixedup with \[and/or\] logic operators, For example: | |
| 26 | + | ||
| 27 | + | ``` pascal | |
| 28 | + | //Befor you need write these conditions to check some conditions: | |
| 29 | + | {$define SOMETHING} | |
| 30 | + | {$define SOMETHINGELSE} | |
| 31 | + | {$ifdef SOMETHING}//Union $IfDef to check multiple conditions | |
| 32 | + | {$ifdef SOMETHINGELSE} | |
| 33 | + | {$ModeSwitch advancedrecords} | |
| 34 | + | {$endif} | |
| 35 | + | {$endif} | |
| 36 | + | ||
| 37 | + | //But with the {$IF} you can check conditions together: | |
| 38 | + | {$if defined(SOMETHING) and defined(SOMETHINGELSE)}//simple and readabl instead of union {$IFDef}`s | |
| 39 | + | {$ModeSwitch advancedrecords} | |
| 40 | + | {$endif} | |
| 41 | + | ||
| 42 | + | {$if defined(somthing) or defined(somethingelse)} | |
| 43 | + | //Whatever you need! | |
| 44 | + | {$endif} | |
| 45 | + | ||
| 46 | + | {$if undefined(what) and defined(somethingelse)} | |
| 47 | + | //Just for note, Another usage! | |
| 48 | + | {$endif} | |
| 49 | + | ``` | |
| 50 | + | ||
| 51 | + | --- | |
| 52 | + | *From the Free Pascal wiki, page "$IF", 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).* |