Difference between revisions of "Utility Module"
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| '''Summary''' | | '''Summary''' | ||
− | |Returns nodes in ''distinct document order'': duplicate nodes will be removed, and the remaining nodes will be returned in [https://www.w3.org/TR/xquery-31/#dt-document-order document order]. | + | |Returns nodes in ''distinct document order'': duplicate nodes will be removed, and the remaining nodes will be returned in [https://www.w3.org/TR/xquery-31/#dt-document-order document order]. As results of path expressions are brought distinct document order before they are returned, the function is equivalent to: |
<syntaxhighlight lang="xquery"> | <syntaxhighlight lang="xquery"> | ||
$nodes/self::node() | $nodes/self::node() | ||
</syntaxhighlight> | </syntaxhighlight> | ||
|} | |} | ||
+ | |||
+ | ==util:root== | ||
{| width='100%' | {| width='100%' |
Revision as of 11:43, 18 January 2021
This XQuery Module contains various small utility and helper functions. Please note that some of the functions are used for internal query rewritings. They may be renamed or moved to other modules in future versions of BaseX.
Contents
Conventions
All functions and errors in this module and errors are assigned to the http://basex.org/modules/util
namespace, which is statically bound to the util
prefix.
Conditions
util:if
Signatures | util:if($condition as item()*, $then as item()*) as item()* util:if($condition as item()*, $then as item()*, $else as item()*) as item()* |
Summary | Alternative writing for the if/then/else expression:
|
Examples |
|
util:or
Signatures | util:or($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 ?: $default </syntaxhighlight> |
Examples |
|
util:within
Signatures | util:within($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
|
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 <= $max </syntaxhighlight> |
Examples |
|
Positional Access
util:item
Signatures | util:item($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: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 - $first + 1) </syntaxhighlight> |
Examples |
|
util:last
Signatures | util:last($sequence as item()*) as item()? |
Summary | Returns last item of a $sequence . Equivalent to:
<syntaxhighlight lang="xquery"> $sequence[last()] </syntaxhighlight> |
Examples |
|
util:init
Signatures | util:init($sequence as item()*) as item()* |
Summary | Returns all items of a $sequence except for the last one. Equivalent to:
<syntaxhighlight lang="xquery"> $sequence[position() < last()] </syntaxhighlight> |
Examples |
|
Node Functions
util:ddo
Signatures | util:ddo($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 $nodes . The path expression /abc is internally represented as util:root(.)/abc</code. Equivalent to:
|
Array and Map Functions
util:array-members
Signatures | util:array-members($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 |
<syntaxhighlight lang="xquery"> let $array := [ (), 2, (3, 4) ] for $member in array:members($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. Better composable and easier to read than the equivalent, but shorter expression:
<syntaxhighlight lang="xquery"> $array ? * </syntaxhighlight> |
Examples |
<syntaxhighlight lang="xquery"> let $array := [ (), 2, [ 3, 4 ] ] return array:values($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 |
<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> |
util:map-values
Signatures | util:map-values($map as map(*)) as item()*
|
Summary | Returns all values of a $map as a sequence. Better composable and easier to read than the equivalent, but shorter expression:
<syntaxhighlight lang="xquery"> $map ? * </syntaxhighlight> |
Examples |
<syntaxhighlight lang="xquery"> let $map := map { 'a': (), 'b': 2, 'c': [ 3, 4 ] } return map:values($map) </syntaxhighlight> |
Helper Functions
util:replicate
Template:Mark Third argument added.
Signatures | 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()*
|
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 |
<syntaxhighlight lang="xquery"> let $nodes := util:replicate(<node/>, 2) return $nodes[1] is $nodes[2] </syntaxhighlight>
<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()*) as xs:anyAtomicType* 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 $collation argument.
|
Examples |
|
util:chars
Signatures | util:chars($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 |
|
Errors
Code | Description |
---|---|
negative
|
The specified number is negative. |
Changelog
- 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
- Version 9.0
- Added: util:replicate
The Module was introduced with Version 8.5.