Array Module

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Revision as of 10:50, 20 November 2023 by Holu (talk | contribs) (Added array:index-where)
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This XQuery Module contains functions for manipulating arrays, which has been introduced with XQuery 3.1 and extended with XQuery 4.0.

Conventions

All functions and errors in this module are assigned to the http://www.w3.org/2005/xpath-functions/array namespace, which is statically bound to the array prefix.

Functions

array:append

Signature 
array:append(
  $array   as array(*),
  $member  as item()*
) as array(*)
Summary Returns a copy of $array with $member attached.
Examples
  • array:append([], 'member1') returns the array ["member1"].

array:build

Signature 
array:build(
  $input	as item()*,	
  $action	as function(item()) as item()*	:= fn:identity#1
) as array(*)
Summary Returns an $array obtained by evaluating the supplied function $action once for each item in the $input sequence.
Examples
  • array:build(1 to 5) returns [1,2,3,4,5]
  • array:build(1 to 5, function { 2 * . }) returns [2,4,6,8,10]
  • array:build(1 to 5, function { 1 to . }) returns [1,(1,2),(1,2,3),(1,2,3,4),(1,2,3,4,5)]
  • array:build(1 to 5, function { array { 1 to . } }) returns [[1],[1,2],[1,2,3],[1,2,3,4],[1,2,3,4,5]]
  • array:build(("red", "green", "blue"), characters#1) returns [("r","e","d"),("g","r","e","e","n"),("b","l","u","e")]

array:empty

Signature 
array:empty(
  $array	as array(*)	
) as xs:boolean
Summary Returns true if the supplied $array contains no members.
Examples
  • array:empty(["a", "b", "c"]) returns false()
  • array:empty([]) returns true()
  • array:empty([[]]) returns false()
  • array:empty([()]) returns false()

array:exists

Signature 
array:exists(
  $array	as array(*)	
) as xs:boolean
Summary Returns true if the supplied $array contains one or more members.
Examples
  • array:exists(["a", "b", "c"]) returns true()
  • array:exists([]) returns false()
  • array:exists([[]]) returns true()
  • array:exists([()]) returns true()

array:filter

Signature 
array:filter(
  $array      as array(*),
  $predicate  as function(item()*) as xs:boolean
) as array(*)
Summary Returns a new array with those members of $array for which $predicate returns true.
Examples The following query returns the array [0, 1, 3]:

<syntaxhighlight lang="xquery"> array:filter( 

 array { 0, 1, -2, 3, -4 },
 function($i) { $i > 0 }

) </syntaxhighlight>

array:flatten

Signature 
array:flatten(
  $items  as item()*
) as item()*
Summary Recursively flattens all arrays that occur in the supplied $items.
Examples
  • array:flatten(["a","b"]) returns the sequence "a", "b".
  • array:flatten([1,[2,3],4]]) returns the sequence 1, 2, 3, 4.

array:fold-left

Signature 
array:fold-left(
  $array   as array(*),
  $zero    as item()*,
  $action  as function(item()*, item()*) as item()*
) as item()*
Summary Evaluates the supplied $action cumulatively on successive members of the supplied $array from left to right, and uses $zero as first argument.
Examples The following query returns 55 (the sum of the integers 1 to 10):

<syntaxhighlight lang="xquery"> array:fold-left( 

 array { 1 to 10 },
 0,
 function($a, $b) { $a + $b }

) </syntaxhighlight>

array:fold-right

Signature 
array:fold-right(
  $array   as array(*),
  $zero    as item()*,
  $action  as function(item()*, item()*) as item()*
) as item()*
Summary Evaluates the supplied $action cumulatively on successive members of the supplied $array from right to left, and uses $zero as first argument.
Examples The following query is equivalent to the expression array:reverse(array { 1 to 5 }):

<syntaxhighlight lang="xquery"> array { 

 array:fold-right(
   array { 1 to 5 },
   (),
   function($a, $b) { $b, $a }
 )

} </syntaxhighlight>

array:foot

Signature 
array:foot(
  $array	as array(*)	
) as item()*
Summary Returns the last member of an array, that is $array(array:size($array)).
Examples
  • array:foot([5, 6, 7, 8]) returns 8
  • array:foot([["a", "b"], ["c", "d"]]) returns ["c","d"]
  • array:foot([("a", "b"), ("c", "d")]) returns 2 results "c" and "d"

array:for-each

Signature 
array:for-each(
  $array   as array(*),
  $action  as function(item()*) as item()*
) as array(*)
Summary Returns a new array, in which each member is computed by applying $action to the corresponding member of $array.
Examples The following query returns the array [2, 3, 4, 5, 6]:

<syntaxhighlight lang="xquery"> array:for-each( 

 array { 1 to 5 },
 function($i) { $i + 1}

) </syntaxhighlight>

array:for-each-pair

Signature 
array:for-each-pair(
  $array1  as array(*),
  $array2  as array(*),
  $action  as function(item()*) as item()*
) as array(*)
Summary Returns a new array obtained by evaluating the supplied $action for each pair of members at the same position in $array1 and $array2.
Examples The following query returns the array [5, 7, 9]:

<syntaxhighlight lang="xquery"> array:for-each-pair( 

 array { 1 to 3 },
 array { 4 to 6 },
 function($a + $b) { $a + $b }

) </syntaxhighlight>

array:get

Signature 
array:get(
  $array     as array(*),
  $position  as xs:integer
) as item()*
Summary Returns the $array member at the specified $position.
Errors FOAY0001: $position is not in the range 1 to array:size($array) inclusive.
Examples
  • array:get(array { reverse(1 to 5) }, 5) returns the value 1.

array:head

Signature 
array:head(
  $array  as array(*)
) as item()*
Summary Returns the first member of $array. This function is equivalent to the expression $array(1).
Errors FOAY0001: The array is empty.
Examples
  • array:head(["a", "b"]) returns "a".
  • array:head([["a", "b"], ["c", "d"]]) returns the array ["a", "b"].

array:index-where

Signature 
array:index-where(
  $array	as array(*),	
  $predicate	as function(item()*, xs:integer) as xs:boolean	
) as xs:integer*
Summary Returns the position in an input $array of members that match a supplied $predicate.
Examples
  • array:index-where([0, (), 4, 9], boolean#1) returns {}
  • array:index-where([0, (), 4, 9], boolean#1) returns (3, 4)
  • array:index-where( array { 1 to 10 }, function {. mod 2 = 0 } ) returns (2, 4, 6, 8, 10) 
  • array:index-where(
  [ "January", "February", "March", "April",
    "May", "June", "July", "August", "September",
    "October", "November", "December" ],
  contains(?, "r")
)
    returns (1, 2, 3, 4, 9, 10, 11, 12) 
  • array:index-where(
  [(1, 2, 3), (4, 5, 6), (7, 8)],
  function($m) { count($m) = 3 }
)
    returns (1, 2)

array:size

Signature 
array:size(
  $array  as array(*)
) as xs:integer
Summary Returns the number of members in $array. Note that because an array is an item, the fn:count function when applied to an array always returns 1.
Examples
  • array:size(array { 1 to 10 }) returns 10.
  • array:size([1 to 10]) returns 1, because the array contains a single sequence with 10 integers.

array:subarray

Signature 
array:subarray(
  $array     as array(*),
  $position  as xs:integer,
  $length    as xs:integer  := ()
) as array(*)
Summary Constructs a new array with with $length members of $array beginning from the specified $position.
The two-argument version of the function returns the same result as the three-argument version when called with $length equal to the value of array:size($array) - $position + 1.
Errors FOAY0001: $position is less than one, or if $position + $length is greater than array:size($array) + 1.
FOAY0002: $length is less than zero.
Examples
  • array:subarray(["a", "b", "c"], 2) returns the array ["b", "c"].

array:put

Signature 
array:put(
  $array     as array(*),
  $position  as xs:integer,
  $member    as item()*
) as array(*)
Summary Returns a copy of $array with $member replaced at the specified $position. Equivalent to $array => array:remove($position) => array:insert-before($position, $member).
Errors FOAY0001: $position is not in the range 1 to array:size($array) inclusive.
Examples
  • array:put(["a", "b", "c"], 2, "d") returns the array ["a", "d", "c"].

array:remove

Signature 
array:remove(
  $array      as array(*),
  $positions  as xs:integer*
) as array(*)
Summary Returns a copy of $array without the member at the specified $positions.
Errors FOAY0001: A position is not in the range 1 to array:size($array) inclusive.
Examples
  • array:append(["a"], 1) returns the array [].

array:insert-before

Signature 
array:insert-before(
  $array     as array(*),
  $position  as xs:integer,
  $member    as item()*
) as array(*)
Summary Returns a copy of $array with one new $member at the specified $position. Setting $position to the value array:size($array) + 1 yields the same result as array:append($array, $insert).
Errors FOAY0001: $position is not in the range 1 to array:size($array) + 1 inclusive.
Examples
  • array:insert-before(["a"], 1, "b") returns the array ["b", "a"].

array:tail

Signature 
array:tail(
  $array  as array(*)
) as array(*)
Summary Returns a new array with all members except the first from $array. This function is equivalent to the expression array:remove($array, 1).
Errors FOAY0001: The array is empty.
Examples
  • array:insert-before(["a"], 1, "b") returns the array ["b", "a"].

array:reverse

Signature 
array:reverse(
  $array  as array(*)
) as array(*)
Summary Returns a new array with all members of $array in reverse order.
Examples
  • array:reverse(array { 1 to 3 }) returns the array [3, 2, 1].

array:join

Signature 
array:join(
  $arrays  as array(*)*
) as array(*)
Summary Concatenates the contents of several $arrays into a single array.
Examples
  • array:join(()) returns the array [].
  • array:join((1 to 3) ! array { . }) returns the array [1, 2, 3].

array:sort

Signature 
array:sort(
  $array      as array(*),
  $collation  as xs:string?                             := (),
  $key        as function(item()*) as xs:anyAtomicType* := ()
) as array(*)
Summary Returns a new array with sorted $array members, using an optional $collation. If a $key function is supplied, it will be applied on all array members. The items of the resulting values will be sorted using the semantics of the lt expression.
Examples
  • array:sort(array { reverse(1 to 3) }) returns [1, 2, 3]
  • array:sort([3,-2,1], (), abs#1) returns [1, -2, 3]
  • array:sort([1,2,3], (), function($x) { -$x }) returns [3, 2, 1]
  • array:sort((1,'a')) returns an error (strings and integers cannot be compared)

Errors

Code Description
FOAY0001 The specified index extends beyonds the bounds of an array.
FOAY0002 The specified length is less than zero.


Changelog

Version 11.0
Version 8.6
  • Updated: array:put collation argument was inserted between first and second argument.
Version 8.5
Version 8.4
  • Removed: array:serialize (use fn:serialize instead)

Introduced with Version 8.0.

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