https://www.drunkenfell.com/index.php?action=history&feed=atom&title=Help%3AVariableHelp:Variable - Revision history2026-06-15T11:23:06ZRevision history for this page on the wikiMediaWiki 1.41.0https://www.drunkenfell.com/index.php?title=Help:Variable&diff=76078&oldid=previmported>Arkalor: moved Help:Variables to Help:Variable2014-04-16T22:53:11Z<p>moved <a href="https://www.drunkenfell.com/index.php?title=Help:Variables&action=edit&redlink=1" class="new" title="Help:Variables (page does not exist)">Help:Variables</a> to <a href="https://www.drunkenfell.com/index.php?title=Help:Variable" title="Help:Variable">Help:Variable</a></p>
<p><b>New page</b></p><div>{{RightToC}}<br />
{{Related|Help:Contents|Wiki Templates}}<br />
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This function allows you to define a variable on a page, use it later in that same page, change its value, possibly to a value given by an expression in terms of the old value, etc. <br />
<br />
It's much like a template, only very lightweight and scoped to only a single page, so you can use many variables on a page without polluting the wiki with huge numbers of templates. <br />
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*This function requires the [http://www.mediawiki.org/wiki/Extension:VariablesExtension Variables] Extension be installed. <br />
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== Assigning a value to a variable ==<br />
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=== #vardefine ===<br />
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:<nowiki>{{#vardefine:</nowiki>''variablename''|''specifiedvalue''}}<br />
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assigns the value ''specifiedvalue'' to the (already existing or hereby introduced) variable ''variablename''.<br />
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=== #vardefineecho ===<br />
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:<nowiki>{{#vardefineecho:</nowiki>''variablename''|''specifiedvalue''}}<br />
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works exactly as <tt>#vardefine</tt>, but the affected value is printed.<br />
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== Retrieving the value of a variable (#var) ==<br />
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The value of the variable ''variablename'' is produced by<br />
:<nowiki>{{#var:</nowiki>''variablename''}}<br />
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If undefined, this produces the empty string; it does not give an error message.<br />
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It's possible to define a value for the case that the variable is undefined or void:<br />
:<nowiki>{{#var:</nowiki>''variablename'' <nowiki>|</nowiki>''defaultvalue''<nowiki>}}</nowiki><br />
This is equivalent to:<br />
:<nowiki>{{#if:</nowiki> <nowiki>{{#var</nowiki>:''variablename''}} |<nowiki>{{#var</nowiki>:''variablename''}} |''defaultvalue''}}<br />
but it's much shorter and better arranged.<br />
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The value can be used in parser functions, etc.<br />
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== #varexists ==<br />
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:<nowiki>{{#varexists:</nowiki>''variablename''}} returns ''1'' if the variable is already defined (also when the value is a void string). If the variable is not defined the return value is void.<br />
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==Examples==<br />
: ''Note that the ParserFunctions extension must also be installed to use #expr''<br />
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Compute 2*a + b:<br />
:<nowiki>{{#expr:2*{{#var:a}}+{{#var:b}}}}</nowiki><br />
Add one to n:<br />
:<nowiki>{{#vardefine:n|{{#expr:{{#var:n}}+1}}}}</nowiki><br />
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