MediaWiki

Extension:ArrayFunctions

MediaWiki extensions manual
ArrayFunctions
Release status: stable
Implementation Parser function
Description Provides a set of pure parser functions that operate on arrays
Author(s) Marijn van Wezel (Wikibase Solutions)
Latest version 1.2.0 (2023-03-03)
Compatibility policy Master maintains backward compatibility.
MediaWiki >=1.35.6
PHP >=7.4
Database changes No
Composer wikibase-solutions/array-functions
License GNU General Public License 2.0 or later
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Quarterly downloads 7 (Ranked 166th)
Translate the ArrayFunctions extension if it is available at translatewiki.net
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Presentation at SMWCon 2022 talking about ArrayFunctions

The ArrayFunctions extension creates an additional set of pure, Parsoid-compatible (see here) parser functions that perform operations on arrays. These parser functions are pure, meaning they do not modify any previously defined arrays and only return a result based on their input arguments.

FunctionsEdit

This extension defines the following parser functions, Lua functions and magic words:

Construct an array or value
Name Description
#af_bool Cast a string to a boolean.
#af_float Cast a string to a float.
#af_int Cast a string to an integer.
#af_list Create a new list from values.
#af_object Create a new object from values.
#af_split Split a string based on a delimiter.
AF_EMPTY The empty array.
mw.af.export Create a new array from Lua.
Extract information from an array
Name Description
#af_count Count the number of values in an array.
#af_exists Check whether a key or index exists in an array.
#af_get Retrieve an element from an array by index.
#af_isarray Check if a value is an array.
#af_print Print an array in a human-readable format.
Create an array from an existing array
Name Description
#af_intersect Compute the intersection of arrays.
#af_keysort Sort a multidimensional array based on the values of a key.
#af_merge Compute the union of arrays.
#af_push Add a value to the end of a list.
#af_set Set a value at an index.
#af_slice Extract a slice from an array.
#af_sort Sort a list.
#af_unique Remove duplicates from an array.
#af_unset Remove a value from an array by index.
Iterate over an array
Name Description
#af_foreach Iterate over an array.
#af_join Recursively join the items of an array together with a separator.
#af_map Apply a callback to each element of a list.
#af_reduce Iteratively reduce the array to a single value using a callback.
Miscellaneous functions
Name Description
#af_if Select one of two alternatives based on a predicate.
#af_template Invoke a template with the values in an array.

This section uses Python's notation for variadic parameters. A parameter prefixed with a single asterisk (*) denotes that a variable number of positional arguments can be passed, and a parameter prefixed with a double asterisk (**) denotes that a variable number of named arguments can be passed.

af_boolEdit

This parser function casts a string to a boolean. This is useful for creating an array containing a boolean.

DescriptionEdit

{{#af_bool: value }}

ParametersEdit

value : string or boolean
The value to cast to a boolean.

Return valuesEdit

Returns the casted boolean.

ExamplesEdit

Create an opaque representation of a boolean 
{{#af_bool: yes }}, {{#af_bool: no }}, {{#af_bool: true }}
 boolean__^__1, boolean__^__0, boolean__^__1
Create an array containing a boolean 
{{#af_print: {{#af_list: {{#af_bool: yes}} }} }}
  • 0: true

af_countEdit

This parser functions counts the number of values in an array.

DescriptionEdit

{{#af_count: array | recursive=recursive }}

ParametersEdit

array : array
The array to count.
recursive : boolean, default=false
Whether to count items recursively. Note that elements containing a list are also counted (see examples below).

Return valuesEdit

The number of items in the array.

ExamplesEdit

Count the number of items in a one-dimensional list 
{{#af_print: {{#af_count: {{#af_list: a | b | c }} }} }}
 3
Count the number of items in a multi-dimensional list 
{{#af_print: {{#af_count: {{#af_list: {{#af_list: a | b }} | {{#af_list: c | d }} }} }} }}
 2
Recursively count the number of items in a multi-dimensional list 
{{#af_print: {{#af_count: {{#af_list: {{#af_list: a | b }} | {{#af_list: c | d }} }} | recursive=true }} }}
 6

af_existsEdit

This parser function checks whether the given key or index exists in the given array.

DescriptionEdit

{{#af_exists: array | key }}

ParametersEdit

array : array
The array to check.
key : string or int
The key to check.

Return valuesEdit

Returns true if array contains key, false otherwise.

ExamplesEdit

Check if a key exists 
{{#af_print: {{#af_exists: {{#af_object: hello=world }} | hello }} }}
 true
Check if an index exists 
{{#af_print: {{#af_exists: {{#af_list: a | b | c }} | 2 }} }}
 true
Check if a nested key exists 
{{#af_print: {{#af_exists: {{#af_get: {{#af_list: a | {{#af_list: b | c }} }} | 1 }} | 2 }} }}
 false

af_floatEdit

This parser function casts a string to a float. This is useful for creating an array containing a float.

DescriptionEdit

{{#af_float: value }}

ParametersEdit

value : string or float
The value to cast to a float.

Return valuesEdit

Returns the casted float.

ExamplesEdit

Create an opaque representation of a float 
{{#af_float: 1.298 }}, {{#af_float: 0 }}
 float__^__1.298, float__^__0
Create an array containing a float 
{{#af_print: {{#af_list: {{#af_float: 1.298 }} }} }}
  • 0: 1.298

af_foreachEdit

This parser function provides a way to iterate over arrays.

DescriptionEdit

{{#af_foreach: array | key_name | value_name | body }}

ParametersEdit

array : array
The array over which to iterate.
key_name : string, default=null
The name to use for the key.
value_name : string, default=null
The name to use for the value.
body : string
The body to return for each iteration.

Return valuesEdit

Returns the resulting wikitext.

ExamplesEdit

Iterate over a list 
{{#af_foreach: {{#af_list: John | Steve | Harry }} | | name | Hello, {{{name}}}!<br/> }}
 Hello, John!
Hello, Steve!
Hello, Harry!
Iterate over an object 
{{#af_foreach: {{#af_object: Hello=John | Hi=Steve | Welcome=Harry }} | greeting | name | {{{greeting}}}, {{{name}}}!<br/> }}
 Hello, John!
Hi, Steve!
Welcome, Harry!

af_getEdit

This parser function retrieves the element with the given index from the given array. If the index does not exist, the empty string is returned.

DescriptionEdit

{{#af_get: array | *indices }}

ParametersEdit

array : array
The array in which to index.
*indices : string
The index. Multiple indices can be given to index nested arrays.

Return valuesEdit

Returns the indexed value, or the empty string if the index does not exist.

ExamplesEdit

Get a top-level element 
{{#af_get: {{#af_list: a | b | c }} | 1 }}
 b
Get a subarray 
{{#af_print: {{#af_get: {{#af_list: a | {{#af_list: b | c }} }} | 1 }} }}
  • 0: b
  • 1: c
Get a nested element 
{{#af_get: {{#af_list: a | {{#af_object: hello=world }} }} | 1 | hello }}
world

af_ifEdit

This parser function selects one of two alternatives based on the given predicate.

DescriptionEdit

{{#af_if: predicate | consequent | alternative }}

ParametersEdit

predicate : boolean
The predicate.
consequent : string
The value to return if the predicate holds (i.e. is true).
alternative : string, default=""
The value to return if the predicate does not hold (i.e. is false).

Return valuesEdit

Returns the consequent if the predicate holds, or the alternative if it is given and the predicate does not hold.

ExamplesEdit

Check if a value is an array 
{{#af_if: {{#af_isarray: not an array }} | A beautiful array! | Not an array! }}
 Not an array!

af_intEdit

This parser function casts a string to an integer. This is useful for creating an array containing an integer.

DescriptionEdit

{{#af_int: value }}

ParametersEdit

value : string or int
The value to cast to an integer.

Return valuesEdit

Returns the casted integer.

ExamplesEdit

Create an opaque representation of an integer 
{{#af_int: 42 }}, {{#af_int: -12 }}
 integer__^__42, integer__^__-12
Create an array containing an integer 
{{#af_print: {{#af_list: {{#af_int: -129}} }} }}
  • 0: -129

af_intersectEdit

 
The intersection of three arrays

This parser function computes the intersection of arrays. This function preserves keys.

DescriptionEdit

{{#af_intersect: array | *arrays }}

ParametersEdit

array : array
The first array.
*arrays : array
The other arrays.

Return valuesEdit

Returns the intersection of the given arrays.

ExamplesEdit

Compute the intersection of two identical arrays 
{{#af_print: {{#af_intersect: {{#af_list: a | b | c }} | {{#af_list: a | b | c }} }} }}
  • 0: a
  • 1: b
  • 2: c
Compute the intersection of two partially overlapping arrays 
{{#af_print: {{#af_intersect: {{#af_list: a | b | c }} | {{#af_list: c | d | e }} }} }}
  • 2: c

af_isarrayEdit

This parser function checks if the given value is an array.

DescriptionEdit

{{#af_isarray: value }}

ParametersEdit

value : mixed
The value to check.

Return valuesEdit

Returns true if value is an array, false otherwise.

ExamplesEdit

Check if an array is an array 
{{#af_print: {{#af_isarray: {{#af_list: a | b | c }} }} }}
 true
Check if a string is an array 
{{#af_print: {{#af_isarray: Hello, World! }} }}
 false

af_joinEdit

This parser function recursively joins the items of an array together with a given separator.

DescriptionEdit

{{#af_join: array | glue }}

ParametersEdit

array : array
The array to join.
glue : string, default=""
The string used to join each item. This parameter recognises the following escape sequences:
\s for spaces
\n for newlines
\\ for backslashes

Return valuesEdit

Returns the joined array.

ExamplesEdit

Join a one-dimensional array 
{{#af_join: {{#af_list: a | b | c }} }}
 abc
Join a one-dimensional array using a separator 
{{#af_join: {{#af_list: a | b | c }} | \s-\s }}
 a - b - c
Join a multi-dimensional array using a separator 
{{#af_join: {{#af_list: a | b | {{#af_list: c | d }} }} | \s-\s }}
 a - b - c - d

af_keysortEdit

This parser function sorts a multidimensional array based on the values of a key.

DescriptionEdit

{{#af_keysort: array | key | descending=descending }}

ParametersEdit

array : array
The array to sort.
key : string
The key of the values on which the sort should be based.
descending : boolean, default=false
Whether to sort in a descending order.

Return valuesEdit

Returns the sorted array.

ExamplesEdit

Sort based on age 
{{#af_print: {{#af_keysort: {{#af_list:
    {{#af_object: name=John | age=56 }} |
    {{#af_object: name=Harry | age=12 }} |
    {{#af_object: name=Bob | age=24 }}
}} | age }} }}
  • 0
    • name: Harry
    • age: 12
  • 1
    • name: Bob
    • age: 24
  • 2
    • name: John
    • age: 56
Sort based on age, in descending order 
{{#af_print: {{#af_keysort: {{#af_list:
    {{#af_object: name=John | age=56 }} |
    {{#af_object: name=Harry | age=12 }} |
    {{#af_object: name=Bob | age=24 }}
}} | age | descending=true }} }}
  • 0
    • name: John
    • age: 56
  • 1
    • name: Bob
    • age: 24
  • 2
    • name: Harry
    • age: 12

af_listEdit

This parser function creates a new list from the given parameters.

DescriptionEdit

{{#af_list: *values }}

ParametersEdit

*values : mixed
The values for the list.

Return valuesEdit

Returns the resulting list.

ExamplesEdit

Create a simple one-dimensional list 
{{#af_print: {{#af_list: a | b | c }} }}
  • 0: a
  • 1: b
  • 2: c
Create a multi-dimensional list 
{{#af_print: {{#af_list: {{#af_list: a | b }} | {{#af_list: c | d }} }} }}
  • 0
    • 0: a
    • 1: b
  • 1
    • 0: c
    • 1: d
Create a list of objects 
{{#af_print: {{#af_list:
    {{#af_object: name=Harry | age=22 }} |
    {{#af_object: name=Bobby | age=29 }}
}} }}
  • 0
    • name: Harry
    • age: 22
  • 1
    • name: Bobby
    • age: 29

af_mapEdit

This parser function applies a callback to each element of a list.

DescriptionEdit

{{#af_map: array | value_name | callback }}

ParametersEdit

array : array
The array to run through the callback.
value_name : string
The name to give to the value in the callback.
callback : string
The callback to apply to each element of the array.

Return valuesEdit

Returns the resulting mapped array.

ExamplesEdit

Appending a string to each element 
{{#af_print: {{#af_map: {{#af_list: a | b | c }} | v | {{{v}}}-appended }} }}
  • 0: a-appended
  • 1: b-appended
  • 2: c-appended
Altering list elements 
{{#af_print: {{#af_map: {{#af_list: {{#af_list: a }} | {{#af_list: b }} }} | v | {{#af_push: {{{v}}} | c }} }} }}
  • 0
    • 0: a
    • 1: c
  • 1
    • 0: b
    • 1: c

af_mergeEdit

 
The union of three arrays

This parser function computes the union of arrays. It merges the elements of one or more arrays together so that the values of one are appended to the end of the previous one.

If the input arrays have the same string key, then the later value for that key will overwrite the previous one. If the arrays contain numeric keys, later values will be appended instead and the later keys will be renumbered.

DescriptionEdit

{{#af_merge: array | *arrays }}

ParametersEdit

array : array
The first array.
*arrays : array
The other arrays.

Return valuesEdit

Returns the union of the given arrays.

ExamplesEdit

Appending a string to each element 
{{#af_print: {{#af_merge: {{#af_list: a | b | c }} | {{#af_list: d | e | f }} }} }}
  • 0: a
  • 1: b
  • 2: c
  • 3: d
  • 4: e
  • 5: f

af_objectEdit

This parser function creates a new object from the given parameters.

DescriptionEdit

{{#af_object: **values }}

ParametersEdit

**values : mixed
The values for the object.

Return valuesEdit

Returns the resulting object.

ExamplesEdit

Create a simple one-dimensional object 
{{#af_print: {{#af_object: a=b | b=c | c=d }} }}
  • a: b
  • b: c
  • c: d
Create a multi-dimensional object 
{{#af_print: {{#af_object: head={{#af_object: title=MediaWiki | meta={{#af_list: {{#af_object: charset=UTF-8 }} }} }} }} }}
  • head
    • title: MediaWiki
    • meta
      • 0
        • charset: UTF-8

af_printEdit

This parser function prints the given value in a human-readable format.

DescriptionEdit

{{#af_print: *values | end=end }}

ParametersEdit

*values : mixed
The values to print.
end : string, default=""
The string to append to the end of each printed value. This parameter recognises the following escape sequences:
\s for spaces
\n for newlines
\\ for backslashes

Return valuesEdit

Returns the value in human-readable form.

ExamplesEdit

Print a boolean 
{{#af_print: {{#af_bool: yes }} }}
 true
Print a list 
{{#af_print: {{#af_list: a | b | c }} }}
  • 0: a
  • 1: b
  • 2: c

af_pushEdit

This parser function adds the given value to the end of the list.

DescriptionEdit

{{#af_push: array | value }}

ParametersEdit

array : array
The array to append the value to.
value : mixed
The value to add.

Return valuesEdit

Returns the array with the value appended.

ExamplesEdit

Push a value 
{{#af_print: {{#af_push: {{#af_list: a | b }} | c }} }}
  • 0: a
  • 1: b
  • 2: c

af_reduceEdit

This parser function iteratively reduces the array to a single value using a callback. It iteratively applies callable to the elements of the given array, so as to reduce the array to a single value. The callable is passed the value of the current iteration, as well as the result of the previous iteration.

DescriptionEdit

{{#af_reduce: array | carry_name | value_name | callable | initial }}

ParametersEdit

array : array
The array to reduce.
carry_name : string
The name to use for the carry.
value_name : string
The name to use for the value.
callable : string
The callback to use for each iteration.
initial : string, default=""
The initial carry to use.

Return valuesEdit

Returns the resulting value.

ExamplesEdit

Using reduction to concatenate values 
{{#af_reduce: {{#af_list: a | b | c }} | c | i | {{{c}}}{{{i}}} }}
 abc
Using reduction to reverse and then concatenate values 
{{#af_reduce: {{#af_list: a | b | c }} | c | i | {{{i}}}{{{c}}} }}
 cba
Using reduction to build an equation 
{{#af_reduce: {{#af_list: 2 | 3 | 5 | 7 | 11 }} | c | i | {{{c}}} + {{{i}}} | 0 }}
 0 + 2 + 3 + 5 + 7 + 11

af_setEdit

This parser function sets the given value for the given index.

DescriptionEdit

{{#af_set: value | array | *indices }}

ParametersEdit

value : mixed
The value to set the index to.
array : array
To array in which to set the index.
*indices : string
The index to set. Multiple indices can be given to index nested arrays.

Return valuesEdit

Returns the array with the given index set to the given value.

ExamplesEdit

Replace an existing value 
{{#af_print: {{#af_set: d | {{#af_list: a | b | c }} | 2 }} }}
  • 0: a
  • 1: b
  • 2: d
Create a new index 
{{#af_print: {{#af_set: far | {{#af_object: foo=bar }} | boo }} }}
  • foo: bar
  • boo: far
Create a new subarray 
{{#af_print: {{#af_set: far | {{#af_object: foo=bar }} | boo | far }} }}
  • foo: bar
  • boo
    • far: far

af_sliceEdit

This parser function extracts a slice from the given array. Keys will be reset and reordered.

DescriptionEdit

{{#af_slice: array | offset | length }}

ParametersEdit

array : array
The array to take a slice from.
offset : integer
The offset at which the slice starts. If non-negative, the slice will start at this given offset. If negative, the sequence will start that far from the end of the array.
length : integer, optional
The length of the slice. If the length is given and positive, then the slice will have that many elements in it. If the length is given and negative, then the slice will stop that many elements from the end of the array. If it is omitted, then the slice will have everything from offset up until the end of the array.

Return valuesEdit

The slice.

ExamplesEdit

Get the first two elements 
{{#af_print: {{#af_slice: {{#af_list: a | b | c }} | 0 | 2 }} }}
  • 0: a
  • 1: b
Get the last element 
{{#af_print: {{#af_slice: {{#af_list: a | b | c }} | -1 }} }}
  • 0: c

af_sortEdit

This parser function sorts the given list.

DescriptionEdit

{{#af_sort: array | descending=descending }}

ParametersEdit

array : array
The array to sort.
descending : boolean, default=false
Whether to sort the list in descending order.

Return valuesEdit

Returns the sorted list.

ExamplesEdit

Sort a list in ascending order 
{{#af_print: {{#af_sort: {{#af_list: b | c | a }} }} }}
  • 0: a
  • 1: b
  • 2: c
Sort a list in descending order 
{{#af_print: {{#af_sort: {{#af_list: b | c | a }} | descending=true }} }}
  • 0: c
  • 1: b
  • 2: a

af_splitEdit

This parser function splits the given string based on a delimiter.

DescriptionEdit

{{#af_split: string | delimiter }}

ParametersEdit

string : string
The string to split.
delimiter : string, default=","
The delimiter to use. This parameter recognises the following escape sequences:
\s for spaces
\n for newlines
\\ for backslashes

Return valuesEdit

Returns the resulting list.

ExamplesEdit

Split a string based on commas 
{{#af_print: {{#af_split: a, b, c }} }}
  • 0: a
  • 1: b
  • 2: c
Split a sentence into words 
{{#af_print: {{#af_split: Lorem ipsum dolor et | \s }} }}
  • 0: Lorem
  • 1: ipsum
  • 2: dolor
  • 3: et

af_templateEdit

This parser function will invoke the given template and pass the values in the given array as arguments.

DescriptionEdit

{{#af_template: name | data }}

ParametersEdit

name : string
The name of the template to invoke. If no namespace is given, it is assumed the page is in the template namespace, otherwise the given namespace is used. The page must exist, must be includable and must be readable by the user, otherwise an error is given.
data : array
The data to pass to the parameters. Values with numeric indices are passed as positional arguments and values with string indices are passed as named arguments.

Return valuesEdit

The expanded template.

ExamplesEdit

Invoking a template with a list 
{{#af_template: Echo | {{#af_list: a | b }} }}
 
{{Echo|a|b}}
Invoking a template with an object 
{{#af_template: Echo | {{#af_object: foo=bar | boo=far }} }}
 
{{Echo|foo=bar|boo=far}}

af_uniqueEdit

This parser function removes duplicate values from the given array. This function does not reset keys.

DescriptionEdit

{{#af_unique: array }}

ParametersEdit

array : array
The array from which to remove duplicates.

Return valuesEdit

Returns the array with duplicates removed.

ExamplesEdit

Remove duplicates from an array 
{{#af_print: {{#af_unique: {{#af_list: a | a | b | c | b }} }} }}
  • 0: a
  • 2: b
  • 3: c

af_unsetEdit

This parser function removes the value associated with the given index from the array and returns the result. Numeric keys are not reset after calling this function.

DescriptionEdit

{{#af_unset: array | *indices }}

ParametersEdit

array : array
The array from which to remove the given key.
*indices : string
The index to remove. Multiple indices can be given to index nested arrays.

Return valuesEdit

Returns the array with the given index removed.

ExamplesEdit

Remove a top-level index 
{{#af_print: {{#af_unset: {{#af_list: a | b | c }} | 2 }} }}
  • 0: a
  • 1: b
Remove a top-level index, keys not reset 
{{#af_print: {{#af_unset: {{#af_list: a | b | c }} | 1 }} }}
  • 0: a
  • 2: c
Remove a nested index 
{{#af_print: {{#af_unset: {{#af_object: foo={{#af_object: bar=quz | far=buz }} }} | foo | bar }} }}
  • foo
    • far: buz

ScribuntoEdit

This extension is particularly useful in combination with Lua, as it can be used to create the array containing data required for the presentation of the page. This array can be exported to work with ArrayFunctions: 

local p = {};

function p.world()
	return mw.af.export({
		["Hello"] = "World"
	});
end

return p;

This module may then be invoked like so: 

{{#af_print: {{#invoke: Hello | world }} }}
  • Hello: World

Magic wordsEdit

The extension defines a number of magic words (variables).

AF_EMPTYEdit

This magic word returns the empty array. This is useful, because it is not possible to create an empty array with #af_list or #af_object.

DescriptionEdit

{{AF_EMPTY}}

Return valuesEdit

Returns the empty array.

InstallationEdit

  • Download and place the file(s) in a directory called ArrayFunctions in your extensions/ folder.
  • Add the following code at the bottom of your LocalSettings.php : 
    wfLoadExtension( 'ArrayFunctions' );
  •   Done – Navigate to Special:Version on your wiki to verify that the extension is successfully installed.

FAQEdit

How can I define an array to be used throughout a page?Edit

It is not possible to directly define an array to be used throughout a page, because this would require sequential processing of extension tags, which is not supported by Parsoid (see Parsoid/Extension API#No support for sequential, in-order processing of extension tags). Instead, you can pass arrays around as template parameters: 

{{My template|{{#af_list:a|b|c}}}}

This way, the array is available in Template:My template as {{{1}}}.

How to iterate over an array?Edit

It is possible to iteratively access elements of an array using #af_foreach: 

{{#af_foreach:{{#af_list:red|green|blue}}||color|<nowiki/>
* {{{color}}} is my favourite.
}}

The expected output from the snipped above is:

  • red is my favourite.
  • green is my favourite.
  • blue is my favourite.

How to use foreach with a delimiter?Edit

Using #af_foreach with a delimiter is not supported. Instead, you can use the #af_map function in conjunction with the #af_join function: 

{{#af_join:{{#af_map:{{#af_list:red|green|blue}}|color|* {{{color}}} is my favourite.}}|\n}}

See alsoEdit

Retrieved from "https://www.mediawiki.org/w/index.php?title=Extension:ArrayFunctions&oldid=5839898"