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In the context of [[wikipedia:MediaWiki|MediaWiki]] markup, a '''parser function''' allows a [[Help:template|template]]-like expression to be evaluated based on one or more function parameters. 

For example, <nowiki>{{lc:AbCdEf}}</nowiki> yields the value: {{lc:AbCdEf}}.

Since the colon is always used, ''parser functions'' are also affectionately known as '''colon functions'''.

==Syntax==
A parser function named "functionname" is invoked as though it were a template except that the initial separator is a colon, e.g.
:<nowiki>{{functionname: parameter 1}} </nowiki>

Additional parameters are separated using the vertical bar "'''|'''", e.g.

:<nowiki>{{functionname: parameter 1 | parameter 2}} </nowiki>

The function name is ''not'' case-sensitive. Many parser function names have a leading hash character "#".

==Standard Parser Functions==

===LC===
Converts text to lowercase.

<nowiki>{{lc:AbCdEf}}</nowiki> gives {{lc:AbCdEf}}.<br />
<nowiki>{{lc:Ä Β Ç}}</nowiki> gives {{lc:Ä Β Ç}}, expected ä β ç.

===UC===
Converts text to uppercase.

<nowiki>{{uc:AbCdEf}}</nowiki> gives {{uc:AbCdEf}}.<br />
<nowiki>{{uc:ä β ß}}</nowiki> gives {{uc:ä β ß}}. Don't expect too much.

===LCFIRST===
Converts the first character to lowercase if required: <nowiki>{{lcfirst:Ab Cd}}</nowiki> gives {{lcfirst:Ab Cd}}.

===UCFIRST===
Converts the first character to uppercase if required: <nowiki>{{ucfirst:aB cD}}</nowiki> gives {{ucfirst:aB cD}}.

===PLURAL===
See [[Help:PLURAL]].

===URLENCODE===
Encodes the string into a format suitable for using as a URL by replacing spaces with "+" and other url formatting characters with their escaped equivalents: <nowiki>{{urlencode:hello world ?&=#/:}}</nowiki> gives {{urlencode:hello world ?&=#/:}}.

'''Warnings:'''
* <tt>urlencode:</tt> encodes spaces as "'''<tt>+</tt>'''", not "'''<tt>_</tt>'''" or the generally supported "'''<tt>%20</tt>'''". 
* Both leading and trailing spaces are stripped:
: <tt><nowiki>{{urlencode:&nbsp;&#160;@&#160;!&nbsp;&#160;}}</nowiki></tt> yields '''{{urlencode:  @ !  }}'''.
* "/" is also encoded, e.g. <tt><nowiki>{{urlencode:/path/file}}</nowiki></tt> yields '''{{urlencode:/path/file}}'''

The pair of characters "'''<tt>&#125;}</tt>'''" must be encoded indirectly
(e.g. using [[:Template:))]]), and similarly for "{{((}}" (using  [[:Template:((]]). "'''<tt>|</tt>'''" can be encoded using [[:Template:!]].

For example, to encode the string "{{((}} and }}", one could write <tt><nowiki>{{urlencode:{{((}} and {{))}}}}</nowiki></tt>, which produces {{urlencode:{{((}} and {{))}}}}

===NS===
Gives the namespace name for a given [[Help:Namespace|namespace]] number or name:

{| class="wikitable"
! Code<br>with Number !! Code<br>with Name !! Returns<br>with Number !! Returns<br>with Name
|-
| <code>{&#123;ns:-2&#125;}</code>
| <code>{&#123;ns:media}}</code>
| {{ns:-2}}
| {{ns:Media}} 
|- 
| <code>{&#123;ns:-1&#125;}</code>
| <code>{&#123;ns:special&#125;}</code>
| {{ns:-1}}
| {{ns:Special}} 
|- 
| <code>{&#123;ns:0&#125;}</code>
| (<small>not applicable</small>) 
| {{ns:0}}
| (<small>not applicable</small>)
|- 
| <code>{&#123;ns:1&#125;}</code>
| <code>{&#123;ns:talk&#125;}</code>
| {{ns:1}}
| {{ns:Talk}} 
|- 
| <code>{&#123;ns:2&#125;}</code>
| <code>{&#123;ns:user&#125;}</code>
| {{ns:2}}
| {{ns:User}} 
|- 
| <code>{&#123;ns:3&#125;}</code>
| <code>{&#123;ns:user_talk&#125;}</code>
| {{ns:3}}
| {{ns:User_talk}}
|- 
| <code>{&#123;ns:4&#125;}</code>
| <code>{&#123;ns:project&#125;}</code>
| {{ns:4}}
| {{ns:Project}}
|-
| <code>{&#123;ns:5&#125;}</code>
| <code>{&#123;ns:project_talk&#125;}</code>
| {{ns:5}}
| {{ns:Project_talk}}
|- 
| <code>{&#123;ns:6&#125;}</code>
| <code>{&#123;ns:image&#125;}</code>
| {{ns:6}}
| {{ns:Image}} 
|- 
| <code>{&#123;ns:7&#125;}</code>
| <code>{&#123;ns:image_talk&#125;}</code>
| {{ns:7}}
| {{ns:Image_talk}}
|- 
| <code>{&#123;ns:8&#125;}</code>
| <code>{&#123;ns:mediawiki&#125;}</code>
| {{ns:8}}
| {{ns:MediaWiki}} 
|- 
| <code>{&#123;ns:9&#125;}</code>
| <code>{&#123;ns:mediawiki_talk&#125;}</code>
| {{ns:9}}
| {{ns:MediaWiki_talk}}
|- 
| <code>{&#123;ns:10&#125;}</code>
| <code>{&#123;ns:template&#125;}</code>
| {{ns:10}}
| {{ns:Template}} 
|- 
| <code>{&#123;ns:11&#125;}</code>
| <code>{&#123;ns:template_talk&#125;}</code>
| {{ns:11}}
| {{ns:Template_talk}}
|- 
| <code>{&#123;ns:12&#125;}</code>
| <code>{&#123;ns:help&#125;}</code>
| {{ns:12}}
| {{ns:Help}} 
|-
| <code>{&#123;ns:13&#125;}</code>
| <code>{&#123;ns:help_talk&#125;}</code>
| {{ns:13}}
| {{ns:Help_talk}}
|- 
| <code>{&#123;ns:14&#125;}</code>
| <code>{&#123;ns:category&#125;}</code>
| {{ns:14}}
| {{ns:Category}} 
|-
| <code>{&#123;ns:15&#125;}</code>
| <code>{&#123;ns:category_talk&#125;}</code>
| {{ns:15}}
| {{ns:Category_talk}}
|-
! colspan="4" align="center" | Namespaces 100 and higher are customized by each site
|- 
| <code>{&#123;ns:100&#125;}</code>
| <code>{&#123;ns:Princeton&#125;}</code>
| {{ns:100}}
| {{ns:Princeton}}
|- 
| <code>{&#123;ns:101&#125;}</code>
| <code>{&#123;ns:Princeton_talk&#125;}</code> 
| {{ns:101}}
| {{ns:Princeton_talk}}
|}

<code><nowiki>{{ns:{{ns:12}}_talk}}</nowiki></code> gives {{ns:{{ns:12}}_talk}}.

Note: <code><nowiki>{{ns:{{SITENAME}}}}</nowiki></code> 
produces <code>{{ns:{{SITENAME}}}}</code>

===URLs===
<!-- 
{| 
| {{evaldemo|localurl:fullpagename|s={{!!}} }}
|}
-->
{| 
| <code><nowiki>{{localurl:fullpagename}}</nowiki></code>
| {{localurl:fullpagename}}
|- 
| <code><nowiki>{{localurl:page|query=x}}</nowiki></code>
| {{localurl:page|query=x}} 
|- 
| <code><nowiki>{{localurl:a&b! c}}</nowiki><br /><nowiki>{{localurle:a&b! c}}</nowiki></code>
| {{localurl:a&b! c}}<br />{{localurle:a&b! c}} 
|- 
| <code><nowiki>{{urlencode:a&b! c}}</nowiki></code>
| {{urlencode:a&b! c}}
|- 
| <code><nowiki>{{fullurl:fullpagename}}</nowiki></code>
| <small>{{fullurl:fullpagename}}</small> 
|- 
| <code><nowiki>{{fullurl:ab}}</nowiki></code>
| <small>{{fullurl:ab}}</small> 
|- 
| <code><nowiki>{{fullurl:a b}}</nowiki></code>
| <small>{{fullurl:a b}}</small> 
|- 
| <code><nowiki>{{fullurl:ab|u=v}}</nowiki></code>
| <small>{{fullurl:ab|u=v}}</small> 
|- 
| <code><nowiki>{{fullurl:m:a b|u=v}}</nowiki></code>
| <small>{{fullurl:m:a b|u=v}}</small> 
|- 
| <code><nowiki>{{fullurl:m:ab|u=v}}</nowiki></code>
| <small>{{fullurl:m:ab|u=v}}</small> 
|- 
| <code><nowiki>{{fullurl:a b|u=v}}</nowiki></code>
| <small>{{fullurl:a b|u=v}}</small> 
|- 
| colspan="2" | <code><nowiki>{{fullurl:a&b!|u=v}}</nowiki> &#160;</code><small>{{fullurl:a&b!|u=v}}</small><br /><code><nowiki>{{fullurle:a&b!|u=v}}</nowiki>&#160;</code><small>{{fullurle:a&b!|u=v}}</small>
|}


For interwiki links localurl and fullurl give the same:
{|
| <code><nowiki>{{localurl:wikipedia:a}}</nowiki><br /><nowiki>{{fullurl:wikipedia:a}}</nowiki></code>
| {{localurl:wikipedia:a}}<br />{{fullurl:wikipedia:a}} 
|}

The parser function <tt>localurl:</tt> replaces spaces by underscores and special characters by escape codes, e.g. {&#123;localurl:a !&#125;} gives {{localurl:a !}}. It is usually preferable to use the more concise <tt>fullurl:</tt> constructs. <code><nowiki>{{fullurl:page}}</nowiki></code> is a shorthand for <code><nowiki>{{SERVER}}{{localurl:page}}</nowiki></code>.

'''Warning''': neither <tt>fullurl:</tt> nor <tt>localurl:</tt> encode spaces or special characters in the ''query-string'' parameter. This can result in broken URLs:

: <tt><nowiki>{{fullurl:m:Special:Contributions|target=Jimbo Wales&limit=10}}</nowiki></tt>
: {{fullurl:m:Special:Contributions|target=Jimbo Wales&limit=10}}

With <tt><nowiki>target={{urlencode:Jimbo Wales}}&amp;limit=10</nowiki></tt> as ''query-string'' it works:

: {{fullurl:m:Special:Contributions|target={{urlencode:Jimbo Wales}}&limit=10}}

=="Hash" Parser Functions==
The "hash" or "#" parser function package has been installed on {{qed}}. This package provides a wide variety of functions including:
* <nowiki>#expr</nowiki> for arithmetic expressions
* <nowiki>#if</nowiki>, #ifeq, [[help:ifexist|#ifexist]], #ifexpr, and #iferror for "logical" functions
* <nowiki>#switch</nowiki> for string comparisons
* <nowiki>#rel2abs</nowiki> and #titleparts for string manipulation
* <nowiki>#time</nowiki> for time/date functionality

See [http://www.mediawiki.org/wiki/Help:Extension:ParserFunctions ParserFunctions] for documentation.

== #language ==
<code>{&#123;#language: ''code''&#125;}</code> gives the local language name of selected RFC 3066 language codes, otherwise it returns the input value as is. For a complete list see the [http://www.iana.org/assignments/language-subtag-registry IANA registry].
:{{evaldemo|#language:da}}
:{{evaldemo|#language:fo}}
:{{evaldemo|#language:zh}}
:{{evaldemo|#language:zh-min-nan}}
:{{evaldemo|#language:ang}}
:{{evaldemo|#language:tlh}} (missing, incomplete list)
:{{evaldemo|#language:frr}} (missing, introduced 2006)
:{{evaldemo|#language:mw}} (no language code as of 2006)

== #macro ==

The '''#macro''' parser function is intended for use in [[Help:template|templates]] in which template variables must be expanded before XML-style [[Help:tags|tags]] are processed. See [[Help:macro]] for details.

==Use of result==
The result, like that of a variable or template, and like a template parameter value, can be used in the following ways:
{| class=wikitable
|-
| the name of a template|| <nowiki> {{ {{lc:ABC}}}}</nowiki> ||  {{ {{lc:ABC}}}}
|-
| the name of a variable|| <nowiki> {{ {{uc:currenttime}}}}</nowiki> ||  {{ {{uc:currenttime}}}}
|-
| the name of a parser function|| <nowiki> {{ {{uc:lc}}:ABC}}</nowiki> ||  {{ {{uc:lc}}:ABC}}
|-
| the name of a template parameter|| <nowiki> {{t2|{{#expr:3-1}}=a}}</nowiki> ||  {{t2|{{#expr:3-1}}=a}}
|-
| the value of a template parameter|| <nowiki> {{t2|{{#expr:3-1}}}}</nowiki> ||  {{t2|{{#expr:3-1}}}}
|-
| a template parameter default value|| <nowiki> {{{1|{{#expr:7-2}}}}}</nowiki> ||  {{{1|{{#expr:7-2}}}}}
|-
| a template parameter definition ( ''name'' = ''value'' )|| <nowiki> {{pab|{{lc:AB=CD}}}}</nowiki> ||  {{pab|{{lc:AB=CD}}}}
|-
| the name of a switch parameter|| <nowiki> {{#switch:2|{{#expr:3-1}}=a}}</nowiki> ||  {{#switch:2|{{#expr:3-1}}=a}}
|-
| the value of a parser function parameter|| <nowiki> {{#ifeq:{{lc:AbC}}|abc|yes}}</nowiki> ||  {{#ifeq:{{lc:AbC}}|abc|yes}}
|-
| a switch parameter definition ( ''name'' = ''value'' )|| <nowiki> {{#switch:ab|{{lc:AB=CD}}}}</nowiki> ||  {{#switch:ab|{{lc:AB=CD}}}}
|-
| the target or label of an internal link|| <nowiki> [[{{lc:ABc}}|{{uc:ABc}}]]</nowiki> ||  [[{{lc:ABc}}|{{uc:ABc}}]]
|-
| the target or label of an external link|| <nowiki> [http://{{lc:ABc}} {{uc:ABc}}]</nowiki> ||  [http://{{lc:ABc}} {{uc:ABc}}]
|}

Parser functions cannot be used inside HTML-style extension tags, e.g.

: <pre> <math>{{#expr:3-1}} \over 3 </math></pre>
produces
: <math>{{#expr:3-1}} \over 3 </math>

The workaround is to use [[Help:macro|#macro]]:
: <pre>{{#macro:math|{{#expr:3-1}} \over 3 }}</pre> 
produces
{{#macro:math|{{#expr:3-1}} \over 3 }}

==Interpretation of a parser function as a template==
In some cases an incorrect call to a parser function is interpreted as a valid invocation of a template. This can result in various anomalies, including anomalous entries in the [[mw:templatelinks table|templatelinks table]].

When writing templates that use parser functions, it is therefore advisable to take certain precautions as described 
[http://meta.wikimedia.org/wiki/Help:parser_function#Interpretation_of_a_parser_function_as_a_template here].
<!--[[mw:Help:parser function#Interpretation of a parser function as a template|here]] -->

==Substitution==
:''See also: '''[[Help:subst]]''' and '''[[wikipedia:Help:Substitution|Help:Substitution]]'''.''

Applying "subst:" to a parser function works:

<nowiki>{{subst:LC:AbC}}</nowiki> gives abc

==See also==
* [http://meta.wikimedia.org/wiki/Help:Variable Help:Variable]
* [http://meta.wikimedia.org/wiki/Help:Colon_function Help:Colon_function]

[[Category:MediaWiki Extensions]]
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