## FANDOM

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A parser function is a special piece of code in MediaWiki which extends the template functionality to perform logical operations. When rendered, parser functions use the parameters included in the definition to print out a specific result.

Parser functions are written out the same way templates are, surrounded by curly brackets. They are most easily identified by having either a colon or a hash sign (#) in the function name (or both, as is in the case of the `{{#if:}}` function).

A list of all parser functions for use on a wiki is visible at Special:Version.

## Step-by-step use

1. Identify the parser function that is appropriate for the task you are trying to do. There is a wide variety of parser functions, so be sure to do your research.
Below this step-by-step is extra information with links to help direct you to full-fledged documentation of each parser function.
2. Identify the proper syntax for the parser function you wish to use.
In this step-by-step guide, we will be using the `{{#ifexpr:}}` (if expression) parser function, which is enabled on each Community by default. Its syntax is:
{{#ifexpr: expression | value if true | value if false }}
3. Fill in the syntax.
{{#ifexpr: 1 > 0 | yes | no }}
In the example above, we filled in the mathematical expression (1 > 0), set the function to say "yes" if 1 > 0 is mathematically correct and say "no" if 1 > 0 is mathematically incorrect.
4. Save the page and verify that the function seems to be returning the expected value. In our example, "yes" should be returned because 1 is indeed greater than 0.
{{#ifexpr: 1 > 0 | yes | no }}yes.
Note what would have happened if we had tweaked the expression but kept the returned values the same. The equation proves false because 0 is not greater than 1 and "no" is returned.
{{#ifexpr: 1 < 0 | yes | no }}no.

While the above example might seem silly, because one should always know 1 > 0, the power of the parser function is revealed when it is passed a parameter. Let's say you are designing an infobox for a wiki about a TV show. You want to include a character's age and determine if they are an adult or not.

If within the infobox you have `{{#ifexpr: {{{Age}}} >= 18 | This character is an adult. | This character is not an adult. }}`, the code would say "This character is an adult" if the given age of the character is at or above 18. If the given age was less than 18, the code would instead say "This character is not an adult."

## Built-in MediaWiki parser functions

The MediaWiki software itself includes multiple parser functions at the core. A full list of these are available here on MediaWiki.org. This page will illustrate the most useful.

`{{fullurl:}}`
Returns the full URL of a given page.
`{{fullurl:Help:Contents}}`http://community.wikia.com/wiki/Help:Contents
`{{#language:}}`
Converts a language code to the language name.
`{{#language:es}}` → Español
`{{lc:}}`
Makes a string lowercase (opposite of `{{uc:}}`).
`{{lc:CASE}}` → case
`{{ns:}}`
Takes a namespace number and tells you what the namespace is.
`{{ns:4}}` → Community Central
`{{plural:}}`
If a given expression equals one, returns the singular value given. If a given expression equals two, returns the plural value given.
`{{plural:1|is|are}}` → is
`{{plural:2|is|are}}` → are

## ParserFunctions extension

The ParserFunctions extension is a popular MediaWiki extension that added a number of useful parser functions on top of the MediaWiki ones listed above. This extension is enabled by default across all of FANDOM. This extension also includes most of the parser functions found in the now deprecated extension StringFunctions, most notably {{#explode}}.

The ParserFunctions extension has functions for mathematical operations, if/else statements, and time functions. To view a complete list of these functions and extremely useful documentation on how to use them, please visit the extension's official help page.

## Other extensions

Quite a few other extensions that are popular on FANDOM add some parser functions. Here are some common ones.

So if an extension you are interested in has a parser function included, please consult that extensions page on MediaWiki.org.