Extension:LoopFunctions

This extension will enable limited looping functionality in the wikitext, where a variable ($n$ by default) is replaced by the current iteration number of the loop. The variable can be used in a plain text or link. Also the result of the whole loop can be put in an expression, e.g. to compute a factorial. However, the loop body is evaluated before replacing the variable, so e.g. a computation inside the loop body, depending on the value of the variable, is not possible.

Per standard the number of iterations is limited to 100 iterations per session.

#for
where n is the count of iteration and the text is the text to be repeated. If, after expansion of templates, parser functions, and variables, the text contains the text $n$ or what is defined by the third parameter, that will be replaced by the current iteration, starting with 1.

Examples
calling the template using the template foo, containing: will result in the text a b c d


 * Sum of squares 1^2 through 5^2: gives 55.
 * Factorial 6 (6!): gives 720.

Compare, using and :  gives 55.

For a list of squares it seems that we can only use "for", not "#for".

Limitation
In the loop body, templates, parser functions, and variables are expanded before replacing the index variable by its values.

Examples:

Parameter of a parser function depending on the index variable:
 * gives ab1ab2ab3; the result is in this case the same as when the repetition was done first, and then the evaluation of each item.
 * gives AB$N$AB$N$AB$N$; the result is in this case not the same, because $n$ is changed to $N$, and therefore not treated as index variable.
 * Applying #expr to an expression containing the index variable does not work: expansion of #expr in e.g. gives the text "Expression error: Unrecognised punctuation character "$"", so this text will be repeated.

Template name depending on the index variable:
 * gives:
 * if the template with the literal name Template:a$n$ does not exist: Template:a1 Template:a2 Template:a3 (the loop body is evaluated as Template:a$n$, after which the loop function repeats that, substituting $n$).
 * if the template with the literal name Template:a$n$ does exist: the result of, i.e., the content is repeated unchanged.

Limitation in combination with VariablesExtension
Within the loop a variable can be assigned a value depending on the loop variable, and the value of this variable can be retrieved.

However, it seems that within the loop the variable cannot be assigned a new value depending on its own current value. Instead the value on entering the loop is taken.

#foreach
The mask is a string in the format prefix$n$suffix where $n$ can be changed via the replacement parameter. The function #foreach, called inside a template, will produce the text for $n$ = 1, 2, 3,... as long as prefix$n$suffix is a template parameter defined in the template call. If the text contains the text $n$ or what is defined by the third parameter, that will be replaced by the current value of $n$.

It seems that the whole call of #foreach is ignored if the loop body contains a template call or a parser function call, or if the loop body does not contain.

Examples
Calling the template using the template foo, containing: will result in the expanded wikitext foo1_bar = b foo2_bar = a

and hence the output

foo1_bar = b foo2_bar = a

Since foo3_bar is not defined, foo4_bar is not listed either; neither are a and 1, the parameter names which exist but do not match the pattern.

Example without prefix or suffix:

The call of Template:Showpars containing  gives:

1 = abc 2 = de 3 = ijk

Content of a template that links to the pages given by the values of the unnamed parameters:

Installation
Copy the following text to extensions/LoopFunctions/LoopFunctions.php and extensions/LoopFunctions/LoopFunctions.i18n.php. Then, include it from LocalSettings.php:

require_once ( 'extensions/LoopFunctions/LoopFunctions.php' );

 * @copyright Copyright © 2006 Carl Fürstenberg * @license http://www.gnu.org/copyleft/gpl.html GNU General Public License 2.0 or later */

if ( !defined( 'MEDIAWIKI' ) ) { die( 'This file is a MediaWiki extension, it is not a valid entry point' ); }

require_once('LoopFunctions.i18n.php');

$wgExtensionFunctions[] = 'wfSetupLoopFunctions'; $wgExtensionCredits['parserhook'][] = array( 	'version' => '1.0.3',	'description' => 'Provides limited looping functionallity in the wikitext',	'name' => 'LoopFunctions', 	'url' => 'http://www.mediawiki.org/wiki/Extension:LoopFunctions',	'author' => 'Carl Fürstenberg (AzaToth)' );

$wgHooks['LanguageGetMagic'][]      = 'wfLoopFunctionsLanguageGetMagic';

class ExtLoopFunctions { public static $mMaxLoopCount = 100; // Maximum number of loops allowed per session private static $mCurrentLoopCount = 0; // number of executed loops this session

public function forHook(&$parser, $nbr_of_loops = 1, $text = '' , $param = '$n$' ) { $return = ''; $text = trim($text); $param = trim($param);

for($i = 0 ; $i < abs ( intval( $nbr_of_loops ) ) ; ++$i ) {

if( ++self :: $mCurrentLoopCount > self :: $mMaxLoopCount ) { return wfMsg( 'loopfunc_max_loops' ); }

$return .= strtr( $text, array( $param => $i + 1 ) );

}

return $parser->replaceVariables( $return, current($parser->mArgStack) , true); }

public function foreachHook(&$parser, $mask = , $text =  , $param = '$n$' ) { $variables = current( $parser->mArgStack ); $param = trim( $param ); $text= trim( $text ); list ( $prefix, $suffix ) = $param == '' ? array( $mask, '' ) : explode ( $param , $mask , 2 );

for($i = 0; array_key_exists( $prefix. ( $i + 1 ). $suffix, $variables ) ; ++$i ) {

if( ++self :: $mCurrentLoopCount > self :: $mMaxLoopCount ) { return wfMsg( 'loopfunc_max_loops' ); }

$return .= strtr( $text, array( $param => $i + 1 ) );

}

return $parser->replaceVariables( $return, $variables , true); }

}

function wfSetupLoopFunctions { global $wgParser, $wgExtLoopFunctions, $wgLoopFunctionsMessages, $wgMessageCache;

$wgExtLoopFunctions = new ExtLoopFunctions; $wgParser->setFunctionHook( 'for', array( &$wgExtLoopFunctions, 'forHook' ) ); $wgParser->setFunctionHook( 'foreach', array( &$wgExtLoopFunctions, 'foreachHook' ) );

foreach( $wgLoopFunctionsMessages as $key => $value ) { $wgMessageCache->addMessages( $value, $key ); } }

function wfLoopFunctionsLanguageGetMagic( &$magicWords, $langCode ) { global $wgLoopFunctionsMagic; if(!in_array($langCode,$wgLoopFunctionsMagic)) $langCode = 'en'; $magicWords = array_merge($magicWords, $wgLoopFunctionsMagic[$langCode]); return true; } ?>

 "Maximum number of allowed loops reached", );

$wgLoopFunctionsMagic['en'] = array(	'for' => array( 0, 'for' ),	'foreach' => array( 0, 'foreach' ), ); ?>