Help:ParserFunctions: Difference between revisions

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{{MovedToMediaWiki|Help:Extension:ParserFunctions}}

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This MediaWiki extension is a collection of parser functions. Parser functions typically have the syntax:

:<nowiki>{{</nowiki>#functionname: argument 1 | argument 2 | argument 3...}}

This module defines four functions at present: <tt>expr</tt>, <tt>if</tt>, <tt>ifeq</tt> and <tt>rand</tt>.

== expr ==

The <tt>expr</tt> function computes mathematical expressions. The supported operators (roughly in order of precedence) are:

; * : Multiplication

; / <span style="font-weight: normal">or</span> div: Division

; + : Addition

; - : Subtraction (or negation)

; mod : Modulo, gives the remainder of a division

; round : Rounds off the number on the left to the specified number of digits after the decimal place, given on the right

; = : Equality

; <> <span style="font-weight: normal">or</span> != : Inequality

; < : Less than

; > : Greater than

; <= : Less than or equal to

; >= : Greater than or equal to

; and : Logical AND

; or : Logical OR

; not : Logical NOT

; ( ) : Grouping operators

The boolean operators consider 0 to be false and 1 to be true.

Example:

<nowiki>{{ #expr: (100 - 32) / 9 * 5 round 0 }}</nowiki>

gives:

{{ #expr: (100 - 32) / 9 * 5 round 0 }}

which is 100&deg;F in &deg;C, rounded to the nearest whole number.

== if ==

The <tt>if</tt> function is an if-then-else construct. The syntax is:

<nowiki>{{</nowiki> #if: ''&lt;condition>'' | ''&lt;then text>'' | ''&lt;else text>'' }}

If the condition is an empty string or consists only of whitespace, then it is considered false, and the ''else text'' is returned. Otherwise, the ''then text'' is returned. The ''else text'' may be omitted, in which case the result will be blank if the condition is false.

Note that the <tt>if</tt> function does '''not''' support "=" signs or mathematical expressions. <nowiki>{{#if: 1 = 2|yes|no}}</nowiki> will return "yes", because the string "1 = 2" is not blank. It is intended as an "if defined" structure. To compare strings, use <tt>ifeq</tt>. To compare numbers, use <tt>ifexpr</tt>.

== ifeq ==

<tt>ifeq</tt> compares two strings, and returns another string depending on the result of that comparison. The syntax is:

<nowiki>{{</nowiki> #ifeq: ''&lt;comparison text 1>'' | ''&lt;comparison text 2>'' | ''&lt;equal text>'' | ''&lt;not equal text>'' }}

== ifexpr ==

<tt>ifexpr</tt> evaluates a mathematical expression and returns one of two strings depending on the result.

<nowiki>{{</nowiki> #ifexpr: ''&lt;expression>'' | ''&lt;then text>'' | ''&lt;else text>'' }}

If the expression evaluates to zero, then the ''else text'' is returned, otherwise the ''then text'' is returned. Expression syntax is the same as for <tt>expr</tt>.

== rand==

The <tt>rand</tt> function gives random numbers in a specified range.

<nowiki>{{</nowiki> #rand: ''&lt;minimum>'' | ''&lt;maximum>'' }}

The presence of this function does not affect the cache lifetime, so the number displayed will typically only change once per edit.

== Installation ==

Download both of these files and put them in a new directory called ''ParserFunctions'' in your [[Mediawiki extensions|extensions]] directory.

* [http://svn.wikimedia.org/svnroot/mediawiki/trunk/extensions/ParserFunctions/Expr.php Expr.php]

* [http://svn.wikimedia.org/svnroot/mediawiki/trunk/extensions/ParserFunctions/ParserFunctions.php ParserFunctions.php]

Then put the following at the end of your [[LocalSettings.php]]:

require_once( "$IP/extensions/ParserFunctions/ParserFunctions.php" );

You can also browse the code tree here:

* [http://svn.wikimedia.org/viewvc/mediawiki/trunk/extensions/ParserFunctions/ ParserFunctions in MediaWiki SVN]

== External Links ==

* [http://mail.wikipedia.org/pipermail/wikitech-l/2006-April/thread.html#34685 The discussion about the ParserFunctions in the Wikitech-l list archive]

* [http://mail.wikipedia.org/pipermail/wikitech-l/2006-April/034892.html ParserFunctions trial]

[[Category:MediaWiki extensions]]