Extension:LoopFunctions
Release status: stable |
|
---|---|
Implementation | Parser function |
Description | Provides limited looping functionality in wikitext |
Author(s) | |
Latest version | 2020-03-26 |
MediaWiki | 1.35+ |
PHP | 5.3+ |
Database changes | No |
License | GNU General Public License 2.0 or later |
Download | |
Quarterly downloads | 10 (Ranked 122nd) |
Translate the LoopFunctions extension if it is available at translatewiki.net | |
The LoopFunctions 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.
Functions
[edit]#for
[edit]{{#for: n | text }}
Where n is the count of iteration and the text is the text to be repeated.
{{#for: n | text | replacement parameter }}
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.
Watch out for gaps, because code generates stringstringstring
|
Using in templates
[edit]Calling the template {{foo | n=4 | list1=a | list3=c | list4=d }}
, if template foo containing: {{#for: {{{n}}} | {{{list$n$}}}<br/>}}
, will result in the wikitext: a<br/>b<br/>c<br/>d<br/>
Using for calculations
[edit]Sum of squares 1^2 through 5^2: {{#expr:{{#for:5|+$n$*$n$}}}}
gives 55
Factorial 6 (6!): {{#expr:1{{#for:6|*$n$}}}}
gives 720
{{#expr:{{for|call=plus square|pv=1|1|2|3|4|5}}}}
gives 55; For a list of squares it seems that we can only use for
, not #for
.Limitation
[edit]In the loop body, templates, parser functions, and variables are expanded before replacing the index variable by its values, i.e.:
- Parameter of a parser function depending on the index variable
-
- Code
{{#for:3|{{lc:Ab$n$}}}}
givesab1ab2ab3
; the result is in this case the same as when the repetition was done first, and then the evaluation of each item. - Code
{{#for:3|{{uc:Ab$n$}}}}
givesAB$N$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.
{{#expr:2*$n$}}
gives the text so this text will be repeated:Expression error: Unrecognised punctuation character "$"
- Code
- Template name depending on the index variable
-
- Code
{{#for:3|{{a$n$}}}}
gives:- if the template with the literal name
Template:a$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{{a*$n$}}{{a*$n$}}{{a*$n$}}
, i.e., the content is repeated unchanged.
- if the template with the literal name
- Code
- Limitation in combination with Extension:Variables
- 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
[edit]Function only for template use.
{{#foreach: mask | text }}
{{#foreach: mask | text | replacement parameter }}
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 {{{$n$}}}.
Example
[edit]Calling the template {{foo | foo2_bar=a | foo1_bar=b | a=12 | 6 | foo4_bar=c }}
using the template foo, containing: {{#foreach: foo$n$_bar | foo$n$_bar = {{{foo$n$_bar}}}<br/>}}
will result in the expanded wikitext foo1_bar = b<br/>foo2_bar = a<br/>
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.
Using without prefix or suffix
[edit]The code {{showpars | abc | de | w=fgh | ijk}}
call Template:Showpars containing {{#foreach: $n$ | $n$ = {{{$n$}}}<br/>}}
and gives:
- 1 = abc
- 2 = de
- 3 = ijk
Content of a template that links to the pages given by the values of the unnamed parameters:
{{#foreach:$n$|[[{{{$n$}}}]]<nowiki> </nowiki>}}
Installation
[edit]- Download and move the extracted
LoopFunctions
folder to yourextensions/
directory.
Developers and code contributors should install the extension from Git instead, using:cd extensions/
git clone https://gerrit.wikimedia.org/r/mediawiki/extensions/LoopFunctions - Add the following code at the bottom of your LocalSettings.php file:
wfLoadExtension( 'LoopFunctions' );
Done – Navigate to Special:Version on your wiki to verify that the extension is successfully installed.