Utility Module

This XQuery Module contains various utility and helper functions.

For all listed functions, equivalent expressions exist in standard XQuery, but code may be better readable with function calls:

<syntaxhighlight lang="xquery"> (: standard XQuery :) let $result := if(exists($sequence)) then $sequence else ('default', 'values') return $result[last()]

(: XQuery with functions of this module :) $sequence => util:or(('default', 'values')) => util:last() </syntaxhighlight>

In addition, various query optimizations create calls to the utility functions.

Conventions

All functions and errors in this module and errors are assigned to the http://basex.org/modules/util namespace, which is statically bound to the util prefix.

Conditions

util:if

Signatures	util:if( $condition as item()* $then as item()* $else as item()* := () ) as item()*
Summary	Alternative writing for the if/then/else expression: If the effective boolean value of $condition is true, the $then branch will be evaluated. Otherwise, $else will be evaluated. If no third argument is supplied, an empty sequence will be returned.
Examples	util:if(true(), 123, 456) returns 123. util:if(0, 'wrong!') returns an empty sequence.

util:or

Signatures	util:or( $items as item()* $default as item()* ) as item()*
Summary	Returns $items if it is a non-empty sequence. Otherwise, returns $default. Equivalent to the following expressions: <syntaxhighlight lang="xquery"> if(exists($items)) then $items else $default, (: Elvis operator :) $items ?: $default </syntaxhighlight>
Examples	util:or(123, 456) returns 123. util:or(1[. = 0], -1) returns -1.

util:count-within

Updated with BaseX 10: Renamed from util:within

Signatures	util:count-within( $sequence as item()* $min as xs:integer $max as xs:integer := () ) as xs:boolean
Summary	Checks if the specified $sequence has at least $min and, optionally, at most $max items. Equivalent to: <syntaxhighlight lang="xquery"> let $count := count($sequence) return $count >= $min and $count <= $max </syntaxhighlight>
Examples	util:count-within(('a', 'b', 'c'), 2) returns true. util:count-within((1 to 1000000000)[. < 10], 3, 6) returns true.

Positional Access

util:item

Signatures	util:item( $sequence as item()* $position as xs:double ) as item()?
Summary	Returns the item from $sequence at the specified $position. Equivalent to: <syntaxhighlight lang="xquery"> $sequence[$position] </syntaxhighlight>
Examples	util:item(reverse(1 to 5), 1) returns 5. util:item(('a','b'), 0) returns an empty sequence.

util:range

Signatures	util:range( $sequence as item()* $first as xs:double $last as xs:double ) as item()*
Summary	Returns items from $sequence, starting at position $first and ending at $last. Equivalent to: <syntaxhighlight lang="xquery"> subsequence($sequence, $first, $last - $first + 1) </syntaxhighlight>
Examples	util:range(//item, 11, 20) returns all path results from (if available) position 11 to 20.

util:last

Signatures	util:last( $sequence as item()* ) as item()?
Summary	Returns last item of a $sequence. Equivalent to: <syntaxhighlight lang="xquery"> $sequence[last()] </syntaxhighlight>
Examples	util:last(reverse(1 to 100)) returns 1.

util:init

Signatures	util:init( $sequence as item()* ) as item()*
Summary	Returns all items of a $sequence except for the last one. Equivalent to: <syntaxhighlight lang="xquery"> $sequence[position() < last()] </syntaxhighlight>
Examples	util:init(1 to 4) returns 1 2 3.

Node Functions

util:ddo

Signatures	util:ddo( $nodes as node()* ) as node()*
Summary	Returns nodes in distinct document order: duplicate nodes will be removed, and the remaining nodes will be returned in document order. As results of path expressions are brought distinct document order before they are returned, the function is equivalent to: <syntaxhighlight lang="xquery"> $nodes/self::node() </syntaxhighlight>

util:root

Signatures	util:root( $nodes as node()* ) as document-node()*
Summary	Returns the document nodes of the specified $nodes. The path expression /abc is internally represented as util:root(.)/abc. Equivalent to: <syntaxhighlight lang="xquery"> $nodes ! / </syntaxhighlight>

util:strip-namespaces

Signatures	util:strip-namespaces( $node as node() $prefixes as xs:string* := () ) as node()
Summary	Removes namespaces with the specified $prefixes from the supplied $node. An empty string can be supplied to remove the default namespace. If no prefixes are specified, all namespaces will be removed.
Examples	Remove all namespaces from an element and its descendants: <syntaxhighlight lang="xquery"> util:strip-namespaces(<xml xmlns='uri' xmlns:prefix='uri2' prefix:name='value'><prefix:child/></xml>) (: yields :) <xml name='value'><child/></xml> </syntaxhighlight> Remove all default namespaces: <syntaxhighlight lang="xquery"> <xml xmlns='uri1'><child xmlns='uri2'/></xml> => util:strip-namespaces() </syntaxhighlight>

Array and Map Functions

util:array-members

Signatures	util:array-members( $array as array(*) ) as array(*)*
Summary	Returns each member of an $array as a new array. Equivalent to: <syntaxhighlight lang="xquery"> for $a in 1 to array:size($array) return [ $array($a) ] </syntaxhighlight>
Examples	Returns three elements with the member values as concatenated text node. <syntaxhighlight lang="xquery"> let $array := [ (), 2, (3, 4) ] for $member in util:array-members($array) return element numbers { $member } </syntaxhighlight>

util:array-values

Signatures	util:array-values( $array as array(*) ) as item()*
Summary	Returns all members of an $array as a sequence. Equivalent to: <syntaxhighlight lang="xquery"> $array ? * </syntaxhighlight>
Examples	Returns the array members as two items: <syntaxhighlight lang="xquery"> let $array := [ (), 2, [ 3, 4 ] ] return util:array-values($array) </syntaxhighlight>

util:map-entries

Signatures	util:map-entries( $map as map(*) ) as map(xs:string, item()*)*
Summary	Returns each entry of a $map as a new map, each with a key and value entry. Equivalent to: <syntaxhighlight lang="xquery"> map:for-each($map, function($key, $value) { map { "key": $key, "value": $value } }) </syntaxhighlight>
Examples	Returns three elements named by the key of the map, and with the entries as concatenated text node. <syntaxhighlight lang="xquery"> let $map := map { 'a': (), 'b': 2, 'c': [ 3, 4 ] } for $entry in util:map-entries($map) return element { $entry?key } { string-join($entry?value) } </syntaxhighlight>

util:map-values

Signatures	util:map-values( $map as map(*) ) as item()*
Summary	Returns all values of a $map as a sequence. Equivalent to: <syntaxhighlight lang="xquery"> $map ? * </syntaxhighlight>
Examples	Returns the map values as two items: <syntaxhighlight lang="xquery"> let $map := map { 'a': (), 'b': 2, 'c': [ 3, 4 ] } return util:map-values($map) </syntaxhighlight>

Helper Functions

util:replicate

Signatures	util:replicate( $input as item()* $count as xs:integer $multiple as xs:boolean := () ) as item()*
Summary	Evaluates $input and returns the result $count times. Unless $multiple is enabled, the input expression is only evaluated once. Equivalent expressions: <syntaxhighlight lang="xquery"> util:replicate($input, $count, true()), (1 to $count) ! $input </syntaxhighlight>
Errors	negative: The specified number is negative.
Examples	util:replicate('A', 3) returns A A A. In the following query, a single new element node is constructed, and true is returned: <syntaxhighlight lang="xquery"> let $nodes := util:replicate(<node/>, 2) return $nodes[1] is $nodes[2] </syntaxhighlight> In this query, two nodes are constructed, and the result is false: <syntaxhighlight lang="xquery"> let $nodes := util:replicate(<node/>, 2, true()) return $nodes[1] is $nodes[2] </syntaxhighlight>

util:intersperse

Signatures	util:intersperse( $items as item()* $separator as item()* ) as item()*
Summary	Inserts the defined $separator between the $items of a sequence and returns the resulting sequence. Equivalent to: <syntaxhighlight lang="xquery"> head($items), for $item in tail($items) return ($separator, $item) </syntaxhighlight>
Examples	Inserts semicolon strings between the three input items: <syntaxhighlight lang="xquery"> fn:intersperse((<_>1</_>, <_>2</_>, <_>3</_>), '; ') </syntaxhighlight>

util:duplicates

Signatures	util:duplicates( $sequence as item()* $collation as xs:string := () ) as xs:anyAtomicType*
Summary	Returns duplicate values in a $sequence. See fn:distinct-values for the applied equality rules and the usage of the $collation argument.
Examples	util:duplicates((1, 2, 1, 1)) returns 1.

util:chars

Signatures	util:chars( $string as xs:string? ) as xs:string*
Summary	Returns all characters of a $string as a sequence. Equivalent to: <syntaxhighlight lang="xquery"> for $cp in string-to-codepoints($string) return codepoints-to-string($cp) </syntaxhighlight>
Examples	util:chars('AB') returns the two strings A and B.

Errors

Code	Description
negative	The specified number is negative.

Changelog

Version 9.7

• Added: util:strip-namespaces
• Updated: util:count-within: Renamed from util:within.

Version 9.5

• Added: util:intersperse, util:within, util:duplicates, util:array-members, util:array-values, util:map-entries, util:map-values
• Updated: util:replicate: Third argument added.

Version 9.4

• Added: util:root

Version 9.3

• Added: util:ddo

Version 9.2

• Added: util:chars, util:init
• Updated: util:item, util:last, util:range renamed (before: util:item-at, util:item-range, util:last-from)

Version 9.1

• Added: util:if, util:or

Version 9.0

• Added: util:replicate

The Module was introduced with Version 8.5.