This XQuery Module contains various small utility and helper functions. Please note that some of the functions are used for internal query rewritings. They may be renamed or moved to other modules in future versions of BaseX.
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
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util:if($condition as item()*, $then as item()*) as item()*
util:if($condition as item()*, $then as item()*, $else as item()*) as item()*
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Summary
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Alternative writing for the if/then/else expression:
- If the effective boolean value of
$condition is true, the $then branch will be evaluated.
- Otherwise,
$else will be evaluated. If no third argument is supplied, an empty sequence will be returned.
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Examples
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util:if(true(), 123, 456) returns 123 .
util:if(0, 'wrong!') returns an empty sequence.
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util:or
Signatures
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util:or($items as item()*, $default as item()*) as item()*
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Summary
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Returns $items if it is a non-empty sequence. Otherwise, returns $default . The function is equivalent to one of the following expressions:
if(exists($items)) then $items else $default
$items ?: $default (see Elvis Operator for more details)
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Examples
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util:or(123, 456) returns 123 .
util:or(1[. = 0], -1) returns -1 .
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util:within
Template:Mark
Signatures
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util:within($sequence as item()*, $min as xs:integer) as xs:boolean
util:within($sequence as item()*, $min as xs:integer, $max as xs:integer) as xs:boolean
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Summary
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Checks if the specified $sequence has at least $min and, optionally, at most $max items. Equivalent to let $count := count($sequence) return $count >= $min and $count <= $max .
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Examples
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util:within(('a', 'b', 'c'), 2) returns true .
util:within((1 to 1000000000)[. < 10], 3, 6) returns true .
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Positional Access
util:item
Signatures
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util:item($sequence as item()*, $position as xs:double) as item()?
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Summary
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Returns the item from $sequence at the specified $position . Equivalent to $sequence[$position] .
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Examples
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util:item(reverse(1 to 5), 1) returns 5 .
util:item(('a','b'), 0) returns an empty sequence.
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util:range
Signatures
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util:range($sequence as item()*, $first as xs:double, $last as xs:double) as item()*
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Summary
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Returns items from $sequence , starting at position $first and ending at $last . Equivalent to subsequence($sequence, $first, $last - $first + 1) .
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Examples
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util:range(//item, 11, 20) returns all path results from (if available) position 11 to 20.
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util:last
Signatures
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util:last($sequence as item()*) as item()?
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Summary
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Returns last item of a $sequence . Equivalent to $sequence[last()] .
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Examples
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util:last(reverse(1 to 100)) returns 1 .
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util:init
Signatures
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util:init($sequence as item()*) as item()*
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Summary
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Returns all items of a $sequence except for the last one. Equivalent to $sequence[position() < last()] .
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Examples
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util:init(1 to 4) returns 1 2 3 .
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Node Functions
util:ddo
Signatures
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util:ddo($nodes as node()*) as node()*
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Summary
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Returns nodes in distinct document order: duplicate nodes will be removed, and the remaining nodes will be returned in document order. All results of path expression are in distinct document order, so the function is equivalent to the expression $nodes/self::node() .
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Signatures
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util:root($nodes as node()*) as document-node()*
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Summary
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Returns the document nodes of the specified $nodes . The function is equivalent to the expression $nodes ! / . The path expression /abc
is internally represented as util:root(.)/abc</code.
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Array and Map Functions
util:array-members
Template:Mark
Signatures
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util:array-members($array as array(*)) as array(*)*
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Summary
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Returns each member of an $array as a new array. Equivalent to: for $a in 1 to array:size($array) return [ $array($a) ] .
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Examples
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- Returns three elements with the member values as concatenated text node.
<syntaxhighlight lang="xquery">
let $array := [ (), 2, (3, 4) ]
for $member in array:members($array)
return element numbers { $member }
</syntaxhighlight>
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util:array-values
Template:Mark
Signatures
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util:array-values($array as array(*)) as item()*
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Summary
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Returns all members of an $array as a sequence. Equivalent to *? , but better composable and easier to read.
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Examples
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- Returns the array members as two items:
<syntaxhighlight lang="xquery">
let $array := [ (), 2, [ 3, 4 ] ]
return array:values($array)
</syntaxhighlight>
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util:map-entries
Template:Mark
Signatures
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util:map-entries($map as map(*)) as map(xs:string, item()*)*
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Summary
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Returns each entry of a $map as a new map, each with a key and value entry. Equivalent to: map:for-each($map, function($key, $value) { map { "key": $key, "value": $value } }) .
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Examples
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- 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 $entry in map:entries($map)
return element { $entry?key } { string-join($entry?value) }
</syntaxhighlight>
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util:map-values
Template:Mark
Signatures
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util:map-values($map as map(*)) as item()*
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Summary
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Returns all values of a $map as a sequence. Equivalent to *? , but better composable and easier to read.
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Examples
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- Returns the map values as two items:
<syntaxhighlight lang="xquery">
let $map := map { 'a': (), 'b': 2, 'c': [ 3, 4 ] }
return map:values($map)
</syntaxhighlight>
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Helper Functions
util:replicate
Template:Mark Third argument added.
Signatures
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util:replicate($input as item()*, $count as xs:integer) as item()*
util:replicate($input as item()*, $count as xs:integer, $multiple as xs:boolean) as item()*
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Summary
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Evaluates $input and returns the result $count times. Unless $multiple is enabled, the input expression is only evaluated once. The function call util:replicate($input, $count, true()) is equivalent to (1 to $count) ! $input .
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Errors
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negative : The specified number is negative.
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Examples
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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 $nodes[2]
</syntaxhighlight>
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util:intersperse
Template:Mark
Signatures
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util:intersperse($items as item()*, $separator as item()*) as item()*
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Summary
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Inserts the defined $separator between the $items of a sequence and returns the resulting sequence. The function is equivalent to
head($items), for $item in tail($items) return ($separator, $item)
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Examples
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Inserts semicolon strings between the three input items:
<syntaxhighlight lang="xquery">
fn:intersperse((<_>1</_>, <_>2</_>, <_>3</_>), '; ')
</syntaxhighlight>
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util:duplicates
Template:Mark
Signatures
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util:duplicates($sequence as item()*) as xs:anyAtomicType*
util:duplicates($sequence as item()*, $collation as xs:string) as xs:anyAtomicType*
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Summary
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Returns duplicate values in a $sequence . See fn:distinct-values for the applied equality rules and the usage of the $collation argument.
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Examples
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util:duplicates((1, 2, 1, 1)) returns 1 .
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util:chars
Signatures
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util:chars($string as xs:string) as xs:string*
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Summary
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Returns all characters of a $string as a sequence. Equivalent to string-to-codepoints($string) ! codepoints-to-string(.) .
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Examples
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util:chars('AB') returns the two strings A and B .
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Errors
Code
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Description
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negative
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The specified number is negative.
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Changelog
- Version 9.5
- Version 9.4
- Version 9.3
- Version 9.2
- Version 9.1
- Version 9.0
The Module was introduced with Version 8.5.