Extension:Loops

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Loops

Release status: stable

Implementation Parser function
Description Provides parser functions for performing loops
Author(s) David M. Sledge (talk), Daniel Werner
Latest version 0.5.0 (2014-04-22)
MediaWiki 1.19+
PHP 5.3+
Database changes No
License GNU General Public License 2.0 or later
Download
README
RELEASE-NOTES
Parameters

ExtLoops::$maxLoops

Hooks used
ParserFirstCallInit

ParserLimitReport
ParserClearState

Translate the Loops extension if it is available at translatewiki.net

Check usage and version matrix; code metrics

The Loops extension provides parser functions for performing loops.

Usage[edit | edit source]

#while[edit | edit source]

{{#while}} performs a loop (i.e. it repeatedly parses a given wiki markup block statement) so long as the condition mark-up evaluates to non-whitespace.

{{
  #while:
  | <condition text>
  | <block statement>
}}

Examples[edit | edit source]

Note: The following examples use the VariablesExtension.

The wiki markup:

{{ #vardefine: i | 0 }}{{
  #while:
  | {{ #ifexpr: {{ #var: i }} < 5 | true }}
  |<nowiki/>
* {{ #var: i }}{{ #vardefine: i | {{ #expr: {{ #var: i }} + 1 }} }}
}}

produces the following:

  • 0
  • 1
  • 2
  • 3
  • 4

{{#while}} can also be used in a template to simulate a numbered array. If the page "Template:Loops Test" contains

{{
  #vardefine: i | 0
}}{{
  #while:
  | {{{ arg{{#var: i }} |}}}
  |<nowiki/>
* {{{ arg{{#var: i }} }}}{{
    #vardefine: i
    | {{ #expr: {{ #var: i }} + 1 }}
  }}
}}

then the wiki-markup

{{Loops Test
|arg0=zero
|arg1=one
|arg2=two
|arg3=three
|arg4=four
}}

produces

  • zero
  • one
  • two
  • three
  • four

It's important to note that whitespace, including newlines, tabs, and spaces, is stripped from the beginning and end of all the arguments of these parser functions. If this is not desirable, adding any non-whitespace characters (including the HTML encoding for a whitespace character &#32;) will prevent further stripping (hence the <nowiki/> tags in the above examples).

#dowhile[edit | edit source]

{{#dowhile}} performs exactly like {{#while}}, with the exception that the block statement is guaranteed to be parsed and displayed (if it results in displayable text) at least once. This is done before the condition text is evaluated.

#loop[edit | edit source]

{{
  #loop: <variable name>
  | <starting value>
  | <number of loops to be performed>
  | <wiki markup>
}}

{{#loop}} repeatedly parses and displays <wiki markup> a number of times equal to the absolute value of <number of loops to be performed>. <Starting value> is placed in a variable (accessible by VariablesExtension's {{#var:}} parser function) using the name <variable name>. After each loop, the variable is incremented by one if <number of loops to be performed> is positive, or decremented by one if <number of loops to be performed> is negative.

Note: From all loop functions, #loop should have the best performance since there is no condition which has to be expanded and validated for each cycle.

Examples[edit | edit source]

The following code:

{{#loop: varname
  | 4
  | 4
  | <nowiki/>
* This is round {{#var:varname}} and we have {{#expr: 7- {{#var:varname}}}} more to go
}}

produces

  • This is round 4 and we have 3 more to go
  • This is round 5 and we have 2 more to go
  • This is round 6 and we have 1 more to go
  • This is round 7 and we have 0 more to go

#forargs (Experimental)[edit | edit source]

{{#forargs}} is to be used in templates. It takes arguments that are passed to the template and puts them in variables accessible by VariablesExtension's {{#var:}} parser function.

{{
  #forargs: <prefix>
  | <key>
  | <value>
  | <block statement>
}}

This function iterates through each argument whose name begins with <prefix>. With each iteration it puts the argument name minus <prefix> into <key> as if calling {{#vardefine: <key> }}. It then takes the value of the argument and puts it into <value> in a similar method. The block statement is then expanded. The block statement may contain {{#var: <key> }} and {{#var: <value> }} to access the stored arguments.

Example[edit | edit source]

If the page "Template:Loops Test" contains

{{
  #forargs: arg
  | key
  | value
  | <nowiki/>
* {{#var: key}} = {{#var: value}}
}}

then the wiki markup

{{Loops Test
| arg1=val1
| spam=spammity
| arg5=val5
| argument=value
}}

produces

  • 1 = val1
  • 5 = val5
  • ument = value

#fornumargs (Experimental)[edit | edit source]

{{
  #fornumargs: <key>
  | <value>
  | <block statement>
}}

{{#fornumargs}} performs similarly to {{#forargs}} with two major differences: It doesn't take a prefix argument, and it only works on numbered arguments whether they're explicitly numbered:

{{Template | 1=one | 2=two }}

or implicitly numbered:

{{Template | one | two }}

Mixing these methods in a single template call may cause values to get overwritten, so be careful.

Examples[edit | edit source]

TBD

Installation[edit | edit source]

  • Download and extract the file(s) in a directory called Loops in your extensions/ folder. If you're a developer and this extension is in a Git repository, then instead you should clone the repository using:
git clone https://gerrit.wikimedia.org/r/p/mediawiki/extensions/Loops.git
  • Add the following code at the bottom of your LocalSettings.php:
require_once "$IP/extensions/Loops/Loops.php";
  • Done! Navigate to "Special:Version" on your wiki to verify that the extension is successfully installed.

Configuration[edit | edit source]

These configuration variables have to be set in the LocalSettings file after inclusion of Loops.

ExtLoops::$maxLoops
This parameter sets the maximum number of loops a page is allowed to perform (default 100). Setting it to -1 lets the loops run within the limits of phps environment. This parameter affects neither the {{#forargs:}} nor {{#fornumargs:}}.
$egLoopsEnabledFunctions
Configuration variable (array) to define which Loops functions should be enabled. By default, all functions are enabled if the Variables extension is installed as well. If the Variables extension is not installed, #loop, #forargs and #fornumargs will be disabled since they don't work without. To enable the fornumargs and forargs functions only, one can use:
$egLoopsEnabledFunctions = array_diff( $egLoopsEnabledFunctions, array( 'forargs', 'fornumargs' ) );

See also[edit | edit source]

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