Gboyers: Updating from http://www.mediawiki.org/wiki/Help:Extension:ParserFunctions

2012-04-18T15:39:38Z

Updating from http://www.mediawiki.org/wiki/Help:Extension:ParserFunctions

Gboyers: /* #if */ fix

2011-08-02T21:11:10Z

#if: fix

← Older revision		Revision as of 21:11, 2 August 2011
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	<nowiki>{{ #if: <condition string> \| <code if true> \| <code if false> }}</nowiki>		<nowiki>{{ #if: <condition string> \| <code if true> \| <code if false> }}</nowiki>

	Putting anything in the <condition string> will output the <code if true> section. If the <condition string> is empty, null zero or white space, the <code if false> section will output (if it exists). If the <code if false> section is not included, and the <condition string> is null/zero/whitespace nothing will output.		Putting anything in the <condition string> will output the [code if true] section. If the <condition string> is empty, null zero or white space, the [code if false] section will output (if it exists). If the [code if false] section is not included, and the <condition string> is null/zero/whitespace nothing will output.

	==#ifexist==		==#ifexist==

Gboyers: New page: {{help|IF}} '''Parser Functions''' are extensions to the MediaWiki software, mainly allowing IF statements. :''Read more at http://meta.wikimedia.org/wiki/ParserFunctions'' ==#expr...

2008-05-16T23:55:40Z

New page: {{help|IF}} '''Parser Functions''' are extensions to the MediaWiki software, mainly allowing IF statements. :''Read more at http://meta.wikimedia.org/wiki/ParserFunctions'' ==#expr...

New page

{{help|[[IF]]}}

'''Parser Functions''' are extensions to the MediaWiki software, mainly allowing IF statements.

:''Read more at http://meta.wikimedia.org/wiki/ParserFunctions''

==#expr==
Expr simply computes a mathematical expression. It uses standard operators, including: <code>+ - * / = > < <= >= != <></code> as well as <code>not, or, and, mod, round</code>, and brackets <code>( )</code> can be used to group operations.

<nowiki>{{ #expr: expression }}</nowiki>

==#if==
The If statement shows something if the condition evaluates to anything other than zero, with the option of displaying alternative text.

<nowiki>{{ #if: <condition string> | <code if true> }}</nowiki>
<nowiki>{{ #if: <condition string> | <code if true> | <code if false> }}</nowiki>

Putting anything in the <condition string> will output the <code if true> section. If the <condition string> is empty, null zero or white space, the <code if false> section will output (if it exists). If the <code if false> section is not included, and the <condition string> is null/zero/whitespace nothing will output.

==#ifexist==
Ifexist returns one of two results based on whether or not a particular page exists.

<nowiki>{{ #ifexist: <page name> | <page exists> | <page does not exist> }}</nowiki>

Standard naming convention applies: the page [[Vehicles]] is accessible from Vehicles or vehicles, but not VEHICLES. Interwiki links and special pages will output as <page does not exist>.

==#ifexpr==
The function #ifexpr evaluates a mathematical expression (like #expr) and returns one of two strings depending on the result.

<nowiki>{{ #ifexpr: <expression> | <then text> | <else text> }}</nowiki>

For example, <nowiki>{{ #ifexpr: 10 > 9 | yes | no }}</nowiki> outputs yes.

===if expression is valid===
If both the <then text> and <else text> are missing from #ifexpr, nothing is output except error messages (such as division by zero). This can be use with #if to determine if an expression is valid, rather than attempting to output the result:

<nowiki>{{ #if: {{#ifexpr: 1=2 }} | invalid | valid }}</nowiki>

The above expression is "valid". The condition {{#ifexpr: 1=2 }} will not output any error is a valid equation, so the output will be blank (as opposed to an error message). The if statement sees no output, so reports the <code if false> statement, which proves the expression is "valid".

If the expression was invalid (such as <nowiki>{{#ifexpr: 2/0 }}</nowiki>), then the #ifexpr would output an error message. The if statement would see positive output (not zero/null/whitespace) and so output the <code if true>. This proves the expression is "invalid".

==#switch==
The function #switch compares a single value against multiple others, returning a string if a match is found.

<nowiki>{{#switch: <comparison value>
| <value1> = <result1>
| <value2> = <result2>
| ...
| <valuen> = <resultn>
| <default result>
}}</nowiki>

If <comparison value> is <value1>, then <result1> will output. If it is <value2>, then <result2> will output. If it is none of these, then <default result> will output.

It is possible to have a fall-through, allowing multiple <values> to have one <result> entry:

<nowiki>{{#switch: <comparison value>
| <value1>
| <value2>
| <value3> = <result1,2,3>
| <default result>
}}</nowiki>

If <comparison value> is <value1> or <value2> or <value3>, then <result1,2,3> will output.

String comparison is case-sensitive. To be made case-insensitive, use the [[Help:Magic Words|Magic Word]] <nowiki>{{lc:}}</nowiki> to force everything to lowercase (or {{uc:}} for upper case):

<nowiki> {{ #switch: A | a=lower | A=UPPER }} gives UPPER
{{ #switch: {{lc:A}} | a=lower | A=UPPER }} gives lower</nowiki>

==#time==
The function #time outputs the time, using a format string similar to that of [http://www.php.net/date PHP Date]:

<nowiki> {{ #time: format }}
{{ #time: format | time }}</nowiki>

For example:

<nowiki> {{ #time: l j F Y | 20070304 }} gives "Sunday 4 March 2007"
{{ #time: l j F Y | -32 days }} gives "Sunday 6 April 2008" (32 days ago)
{{ #time: H:i | +6 hours }} gives "20:17" (6 hours later than UTC)</nowiki>

==#rel2abs==
rel2abs converts a relative path to an absolute path:

<nowiki> {{ #rel2abs: path }}
{{ #rel2abs: path | base path }}</nowiki>

* If standing in Help:Foo/bar and is calling <nowiki>{{ #rel2abs: ../baz }}</nowiki>, the result will be Help:Foo/baz
* If standing in Help:Foo and is calling <nowiki>{{ #rel2abs: ../baz }}</nowiki>, the result will be baz

If you try to go up too many levels (an invalid relative path) an error will be output.

===if relative path exists===
This can be used in combination with #ifexist to determine whether a path exists:

<nowiki> {{ #ifexist: {{#rel2abs: .. }} | '..' exist | '..' does not exist }} gives '..' does not exist
{{ #ifexist: {{#rel2abs: . }} | '.' exist | '.' does not exist }} gives '.' exist</nowiki>

==#titleparts==
Titleparts returns a number of slash-separated segments of given a page name, starting from a specified segment.

<nowiki>{{ #titleparts: pagename | num | starting_from }}</nowiki>

This returns num slash-separated segments of pagename, starting from the specified starting segment.

<nowiki> "{{#titleparts:Help:Link/a/b|0|}}" gives "Help:Link/a/b"
"{{#titleparts:Help:Link/a/b|2|}}" gives "Help:Link/a"
"{{#titleparts:Help:Link/a/b|2|2}}" gives "a/b"
"{{#titleparts:Help:Link/a/b|1|3}}" gives "b"
"{{#titleparts:Help:Link/a/b|1|-1|}}" gives b</nowiki>

==Notes==

*Applying "subst:" to a parser function works, provided that there is no space between "subst:" and "#".
*The page to which #ifexist is applied (the page you're checking) is registered as link target of a link from the page with the #ifexist code on
* div is not integer division and is redundant, use / (slash) for real divisions.
* mod uses PHP's % operator, which is different from modulo-operators in all other programming languages, see also template:mod ( talk edit history links ) and 6068.
* mod sometimes returns wrong results for the same input values, see 6356 and /MOD10000. Update: values less than 1E+12 are apparently not affected.
* Under certain conditions round 0 results in -0 instead of 0. For an expression x using 0+(x) fixes this oddity.

===Table Syntax===
Currently wiki pipe table syntax doesn't work inside conditionals, but this can be worked around by using [[Template:pipe|<nowiki>{{pipe}}</nowiki>]] to replace using '''|''' for the table syntax.

Help:Parser Functions - Revision history

Gboyers: Updating from http://www.mediawiki.org/wiki/Help:Extension:ParserFunctions

Gboyers: /* #if */ fix

Gboyers: New page: {{help|IF}} '''Parser Functions''' are extensions to the MediaWiki software, mainly allowing IF statements. :''Read more at http://meta.wikimedia.org/wiki/ParserFunctions'' ==#expr...