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Extension:Arrays

Issue tracker: #mediawiki-extensions-arrays
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Warning Warning: This extension is incompatible with plans to parallelize parsing, as is intended by the use of Parsoid . Therefore, the future of this extension is uncertain, and it is expected to become incompatible with the standard MediaWiki parser within a few years. For further information, see T250963 and No support for sequential, in-order processing of extension tags .
MediaWiki extensions manual
Arrays
Release status: stable
Implementation Parser function
Description Enhances parser with array functions.
Author(s) Li Ding, Jie Bao, Daniel Werner
Latest version 2.2.1 (2020-12-08)
MediaWiki 1.31+
Database changes No
License MIT License
Download
Download extension
Git [?]:

README
CHANGELOG
Parameters
  • $wgArraysCompatibilityMode
  • $wgArraysExpansionEscapeTemplates
Hooks used
Quarterly downloads 36 (Ranked 98th)
Translate the Arrays extension if it is available at translatewiki.net
Issues Open tasks · Report a bug

The Arrays extension (formerly known as ArrayExtension) creates an additional set of parser functions that operate on arrays.

Functions

This extension defines the following parser functions:

Group Functions
Construct an array, (with unique, sort, print options) #arraydefine
Extract information from an array #arrayprint, #arrayindex, #arraysize, #arraysearch, #arraysearcharray, #arrayslice
Alter an array #arrayreset, #arrayunique, #arraysort
Interaction between several arrays #arraymerge, #arrayunion, #arrayintersect, #arraydiff
In case Extension:HashTables is installed, for array/hash-table interaction #hashtoarray , #arraytohash

Constructing arrays

arraydefine

This function constructs an array (identified by "key") using a list of "values" separated by the "delimiter". The variable can be accessed by other functions later.

Syntax:

{{#arraydefine:key | values | delimiter | options}}

Notes:

  • "values" is a list of strings separated by "delimiter".
  • The resulting array is an array of strings.
  • The default delimiter is ',' if not specified, a delimiter can be a string (the white-spaces surrounding delimiter will be trimmed) or a Perl regular expression, e.g. /\s*,\s*/ (see preg_split).
  • Users can define an empty array (see example).
  • Users can specify options including unique, sort, and print (see example).
    • Options are ignored unless a delimiter is also specified.

Examples:

Define a one-element array named 'a' 
{{#arraydefine:a|red}}
Define a four-element array named 'b', use default delimiter (',') 
{{#arraydefine:b|orange, red, yellow, yellow}}
Define/set an empty array named 'c' 
{{#arraydefine:c}}
Define a two-element array named 'd', using ';' as delimiter 
{{#arraydefine:d|apple; pear|;}}
Define a three-element array named 'e', using the regular expression /\s*[;,]\s*/ as delimiter 
{{#arraydefine:e|apple, pear; orange|/\s*[;,]\s*/}}
Define a three-element array named 'f', use delimiter (','), "unique, sort=desc, print=list" options (the array elements are unique, sorted in descending order and being printed). For more option-values of sort, see #arraysort. 
{{#arraydefine:f|orange, red, yellow, yellow |, |unique, sort=desc, print=list}}

Working with arrays

Extraction

arrayprint

This function prints the values of an array in customizable format.

Syntax: 

{{#arrayprint:key|delimiter|pattern|subject|options}}

Notes:

  • subject accepts wiki links, templates and parser functions.
  • Within the subject, you don't have to escape pipe characters '|'. Within the whole construct, the pattern will be searched and replaced with the current (escaped) array value of each loop. Finally, the whole string will be parsed and put into an array of results which will be imploded with delimiter as separator.
  • In case the array which should be printed doesn't exist, an empty string will be returned (Introduced in 1.4 alpha, part of compatibility mode).
  • The default delimiter is language dependent, for English it is ', ' (Introduced in 2.0, part of compatibility mode).

Examples:

Task Example code Output (the array b is defined above)
Print - using language dependent default list delimiter 
{{#arrayprint:b}}
  • orange, red, yellow, yellow
Print - without delimiter 
{{#arrayprint:b | }}
  • orangeredyellowyellow
Print - using '‎<br />' (line-break) as delimiter 
{{#arrayprint:b |<br/> }}
 orange

red

yellow

yellow

Pretty list output where the last two elements are chained with an ' and ' (or the local languages equivalent). Even though the delimiter parameter is empty, ', ' (or the languages equivalent) will be used since it wouldn't be pretty otherwise. 
{{#arrayprint:b ||@ |@ |print=pretty }}
Embed wiki link to categories 
{{#arrayprint:b |<br/> |@@@@ |[[:Category:@@@@|@@@@]] }}
 orange

red

yellow

yellow

Define a Semantic MediaWiki property value 
{{#arrayprint:b |<br/> |@@@@ |[[prop1::@@@@]] }}
Embed parser function 
{{#arrayprint:b |<br/> |@@@@ |length of @@@@:{{#len:@@@@}} }}
Embed template (with parameters) 
{{#arrayprint:b|<br/>|@@@@|{{template|prop2|@@@@}} }}

arrayindex

This function prints the value of an array (identified by key) at position index.

Syntax: 

{{#arrayindex:key|index|default}}

Notes:

  • Invalid index (non-number, out of bound) will result in printing an empty string.
  • The index is 0-based, i.e. the first element's index is 0.
  • Negative indexes will return an element that far from the end (e.g. -1 would be the arrays last element).
  • default will be returned in case the array doesn't exist, the key doesn't exist within the array or if the value is an empty string.

Examples:

Third element within array a 
{{#arrayindex:a |2 }}
Last element within array b 
{{#arrayindex:b |-1 }}
Print default value for invalid index 
{{#arrayindex:c |foo |bad value }}

arraysize

This function returns the size (number of elements) of an array.

See https://php.net/function.count In case the given array doesn't exist the output of the function will be a void string instead of a number. This allows to check whether the array exists.

Syntax: 

{{#arraysize:key}}

Examples:

Size of array a: 
{{#arraysize:a}}
Check whether array a exists or not: 
{{#if: {{#arraysize:a}} | ''array exists'' | ''array not defined'' }}

arraysearch

This function returns the index of the first occurrence of the 'value' in the array (identified by 'key') starting from the position identified by 'index' parameter, and returns an empty string when failed. When yes and/or no specified, this will expand the value set to yes if found, value of no otherwise. See https://php.net/function.array-search

Syntax: 

{{#arraysearch:key|value|index|yes|no}}


Examples:

Return index of first occurrence of a value 
{{#arraysearch:b|white}}
{{#arraysearch:b|red}}
use offset
{{#arraysearch:b|red|0}}
{{#arraysearch:b|red|2}}
use preg regular expression match
{{#arraysearch:b|/low/}}
{{#arraysearch:b|/LOW/i}} - case insensitive
{{#arraysearch:b|low}}
use yes no print option
{{#arraysearch:b|white|0|yes|no}}
{{#arraysearch:b|yellow|0|yes|no}}

arraysearcharray

This function searches an array (identified by key) and creates a new array (identified by new_key) from the search with all the results. The search criteria value can be a string or a regular expression. If index is given the search will start there, limit can define the maximum search results. The parameter identified by transform can be used if value is a regular expression. It can transform the result of the matched entries into the new_key array like PHP preg_replace would do it.

Syntax: 

{{#arraysearcharray:new_key|key|value|index|limit|transform}}

Notes:

  • If value is a string, the new_key array will only contain entries of exact this string.
  • Negative index values like -n can be used to search the last n entries only.
  • If Extension:Regex Fun is available within the wiki, Regex Fun's e modifier can be used within the regex. This has nothing to do with PHPs e modifier (which would be a security breach). With active e modifier the transform string will be parsed after back-refs are inserted, after that it will replace the actual match.

Examples:

Find all entries in array 'a' that start with A followed by a space and put them into a new array 'x'. 
{{#arraysearcharray:x |a |/^A\s.+/ }}
Searching all entries of array 'a' which end with numbers and put the numbers only into a new array 'y'. 
{{#arraysearcharray:y |a |/^.*?(\d+)$/ |0 |-1 | $1 }}
Searching all entries of array 'a' which end with numbers and put the length of these items into the new array (this requires Regex Fun extension). 
{{#arraysearcharray:y |y |/^.*?\d+$/e |0 |-1 | {{#len:$0}} }}
Remove empty values from array 'a'. 
{{#arraysearcharray:a|a|/\S+/}}

arrayslice

This function extracts a sub-array from an array (identified by 'key') into a new array (identified by 'new_key').

See https://php.net/function.array-slice

Syntax: 

{{#arrayslice:new_key|key|offset|length}}

Notes:

  • Offset indicates starting point of slice, it can be non-negative number or negative number for backwards index (e.g. the last element of the array's offset is -1). Offset is different from index (which must be non-negative number)
  • Length indicates how many element to extract. If it is omitted, then the sequence will have everything from offset up until the end of the array.
  • If offset is no less than array size, empty array will be returned, if offset if no greater than negative array size, a new array with all elements will be returned.

Examples:

Extract a two-element slice starting from the element at offset 1. 
{{#arrayslice:x|b|1|2}}
Extract a two-element slice starting from the element at offset -2. 
{{#arrayslice:x|b|-2|2}}

Alteration

Functions which alter an array directly instead of creating a new array.

arrayunique

This function converts an array (identified by 'key') into a set (no duplicated members, no empty element).

See https://php.net/function.array-unique

Syntax: 

{{#arrayunique:key}}

Example:

Convert array to set. 
{{#arrayunique:b}}

arrayreset

This function will unset some or all defined arrays.

Syntax: 

{{#arrayreset:}} <!-- will unset ALL arrays -->
{{#arrayreset:key1 |key2 |... |key-n }}

Notes:

  • Using arraysize on them will return an empty string instead of 0, so they are really unset, not empty. To simply empty an array one can use {{#arraydefine:key}}.
  • Prior to version 1.4 alpha ',' is used to separate several arrays which should be unset.

arraysort

This function sorts an array in the following order.

Syntax: 

{{#arraysort:key|order}}

Note:

  • Each array element is being treated as a string, this means numbers might not be ordered as expected.

Examples:

Sort an array. 
{{#arraysort:x|desc}}
Randomize an array. 
{{#arraysort:x|random}}
Reverse an array. 
{{#arraysort:x|reverse}}

Interaction

Functions which work with more than one array, creating one new array or overwriting an existing one as result. Since version 2.0, these functions can interact with more than just two arrays at a time. In case they deal with only one array, they simply create a copy of that array. Any non-existent arrays will simply be ignored by these functions.

arraymerge

This function merges values of two or more arrays into a new array (identified by new_key).

See https://php.net/function.array-merge

Syntax: 

{{#arraymerge:new_key |key1 |key2 |... |key-n }}

Examples:

Merge two arrays. 
{{#arraymerge:x |a |b }}
Duplicate an array (keep the third argument of arraymerge empty). 
{{#arraymerge:x |b }}

arrayunion

This function merges values of two or more arrays into a new array (identified by new_key) without duplicated values.

Syntax: 

{{#arrayunion:new_key |key1 |key2 |... |key-n }}

Notes:

  • This is a set operator, i.e., the returned array is a set without duplicated values.
  • This is equal to arraymerge with arrayunique afterwards.

Example:

Union of three arrays. 
{{#arrayunion:x |a |b |c }}

arraydiff

This function computes the (set theoretic) difference of two or more arrays. The result array is identified by new_key. The returned array is a set that contains elements of the first given array (identified by key1) which are not defined within any of the other arrays. See https://php.net/function.array-diff

Syntax: 

{{#arraydiff:new_key |key1 |key2 |... |key-n }}

Note:

  • This is a set operator, i.e. the returned array is a set without duplicated values.
  • This function can be used to test sub-class relation.

Examples:

Diff (b-a) 
{{#arraydiff:x |b |a }}
Diff (a-b) 
{{#arraydiff:x |a |b }}
Diff (a-(b+c)) 
{{#arraydiff:x |a |b |c }}

arrayintersect

This function computes the set theoretic intersection of two or more given arrays. The result array is identified by new_key. See https://php.net/function.array-intersect

Syntax: 

{{#arrayintersect:new_key |key1 |key2 |... |key-n }}

Note:

  • This is a set operator, i.e., the returned array is a set without duplicated values.

Example:

Intersect of three arrays put into new array x 
{{#arrayintersect:x |a |b |c }}

Installation

  • Download and move the extracted Arrays folder to your extensions/ directory.
    Developers and code contributors should install the extension from Git instead, using:cd extensions/
    git clone https://gerrit.wikimedia.org/r/mediawiki/extensions/Arrays
  • Add the following code at the bottom of your LocalSettings.php file: 
    wfLoadExtension( 'Arrays' );
  • Configure as required.
  • Yes Done – Navigate to Special:Version on your wiki to verify that the extension is successfully installed.

Configuration

Arrays 2.0 introduces two configuration variables:

$egArraysCompatibilityMode
($egArrayExtensionCompatbilityMode in 1.4 alpha) Set to true, this will activate the compatibility mode which will bring back the behavior of the old ArrayExtension 1.3.2 as far as possible. This is because in Version 2.0 several breaking changes have been introduced. So using this compatibility mode allows a smooth switch from 1.x to 2.x Arrays extension. By default, compatibility mode is inactive. If you have been using the old ArrayExtension within your wiki before, you might want to take a look at that list and adjust your templates before switching to Arrays without compatibility mode.
$egArraysExpansionEscapeTemplates
Contains a key-value pair list of characters that should be replaced by a template or parser function call within array values included into an #arrayprint. By replacing these special characters before including the values into the string which is being expanded afterwards, array values can't distract the surrounding MW code. Otherwise the array values themselves would be parsed as well. By default this will escape the following characters with the following template or parser function calls:
  • = = {{=}} ("Template:=" should print '=')
  • | = {{!}} ("Template:!" should print '|')
Note Note: Starting with MW 1.24.0 it is no longer necessary to create "Template:!" since its purpose is served by the new {{!}} magic word.
  • {{ = {{((}} ("Template:((" should print '{{')
  • }} = {{))}} ("Template:))" should print '}}')
Make sure these templates or parser functions exist within your wiki or change this variable accordingly. If this is not set up properly, #arrayprint might print unexpected values in case one of these character sequences is being used within array values.
$egArraysExpansionEscapeTemplates also can simply be set to null, in this case it switches back to pre 2.0 behavior where array values with these character sequences did break the given subject code within #arrayprint. If the compatibility mode is active, this will always be treated as set to null.

FAQ

Iteratively accessing array elements

It is possible to iteratively access elements of an array using #arrayprint or Extension:Loops .

Using arrayprint

<!-- define an array -->
{{#arraydefine:colors|Red,Blue,Yellow}}

{{#arrayprint:colors||@@@@|<nowiki/>
* length of @@@@: {{#len:@@@@}}
}}

Below is the expected output:

  • length of Red: 3
  • length of Blue: 4
  • length of Yellow: 6

More examples can be found at the former Tetherless World Wiki.

Reusing keys

Once an array previously defined is printed, the same key can be reused for another array further down the page. As long as this sequence is observed, there is no need to define a unique key for every array.

Using Loops extension

For more complex tasks it is possible to loop through an array using the Loops extension. 

{{ #arraydefine: colors | red;#FF0000, green;#00FF00, blue;#0000FF }}
{{
  #loop: i
  | 0                       <!-- loops start value for {{ #var:i }} -->
  | {{ #arraysize:colors }} <!-- number of loops -->
  | <nowiki/>
* {{
    #arraydefine: val | {{ #arrayindex:colors | {{ #var:i }} }} | ;
  }}
  <span style="color:{{ #arrayindex: val | 1 }}">
  {{ #arrayindex: val | 0 }}
  </span>
}}

This would output something like:

  • red
  • green
  • blue

Working with Extension:Semantic MediaWiki

There are two ways populating an array with semantic data. The first solution, using Semantic Result Formats is faster and more reliable, also works with complex data sets including record data and multiple values for one property.

Using Extension:Semantic Result Formats

Semantic Result Formats (SRF) introduces the Array format in version 1.6.1. It can be used to query data which will automatically be stored within an Extension:Arrays array. This is the preferred solution dealing with semantic data in arrays. Details can be found on the semantic-mediawiki.org.

Example: 

{{#ask: [[Category:Color]][[:+]] |format=array |name=colors}}
{{#arrayprint: colors}}

Using a standard query

If you can't use the SRF solution above, Arrays also allows to populate an array using a SMW query result of the list format:

Example A: To create a list of instances of the class 'Color' 

{{#arraydefine:colors|{{#ask:[[Category:Color]][[:+]] |sep =, |limit=1000}} }}

Example B: To create a unique list of values of property 'has color' 

{{#arraydefine:colors|{{#ask:[[has color::+]][[:+]] |?color= |mainlabel=- |sep =, |limit=1000}} |,|unique}}

Example C: To deal with 2D array generated by SWM query (e.g. record-type property) 

given a 2D array "red;#da2021, yellow;#fcff00, green;#00ff00"

1. create an array 'colors'
{{#arraydefine:colors|red;#da2021, yellow;#fcff00, green;#00ff00}}

2. split the first element of 'colors' into another array 'colors0'
{{#arraydefine:color0|{{#arrayindex:colors|0}}|;}}

Notes:

  • semantic query parameters
    • limit=1000 option is used to exhaust all returned results of the semantic query
    • sep=, option is used to set the separator for entries of the results
    • mainlabel=- option to cut off the page column

Working with Extension:DynamicPageList3

In a similar way as described above for SMW the Arrays extension can be used to store results of a DPL query. A result list can be inverted. We collect all parameter values which are used by certain pages when they include a given template. We store pairs of template parameter value and pagename. Then we sort the array and print the pairs. If consecutive array elements have the same first part (i.e. the parameter values are identical), the first part is only printed once. Thus we can construct a simple inverted index. The same mechanism could be applied to other problems as well.


See also

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