Difference between revisions of "Utility Module"

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This [[Module Library|XQuery Module]] contains various utility and helper functions.
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This [[Module Library|XQuery Module]] contains some utility and helper functions.
  
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For all listed functions, equivalent expressions exist in standard XQuery, but code may be better readable with function calls:
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With {{Announce|Version 11}}, many functions of this module have been removed as they are now part of the official specification:
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<syntaxhighlight lang="xquery">
 
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(: standard XQuery :)
 
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let $result := if(exists($sequence)) then $sequence else ('default', 'values')
 
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return $result[last()]
 
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(: XQuery with functions of this module :)
 
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$sequence
 
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=> util:or(('default', 'values'))
 
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=> util:last()
 
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</syntaxhighlight>
 
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In addition, various query optimizations create calls to the utility functions.
 
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With {{Announce|Version 11}}, various functions of this module have been removed as they are now part of the official specification:
 
  
 
{|
 
{|
Line 172: Line 157:
 
=> util:strip-namespaces('')
 
=> util:strip-namespaces('')
 
</syntaxhighlight>
 
</syntaxhighlight>
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|}
 
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=Array and Map Functions=
 
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==util:map-entries==
 
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{| width='100%'
 
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|- valign="top"
 
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| width='120' | '''Signature'''
 
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|<pre>util:map-entries(
 
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  $map  as map(*)
 
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) as map(xs:string, item()*)*</pre>
 
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|- valign="top"
 
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| '''Summary'''
 
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|Returns each entry of a {{Code|$map}} as a new map, each with a {{Code|key}} and {{Code|value}} entry. Equivalent to:
 
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<syntaxhighlight lang="xquery">
 
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map:for-each($map, function($key, $value) {
 
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  map { "key": $key, "value": $value }
 
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})
 
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</syntaxhighlight>
 
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|- valign="top"
 
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| '''Examples'''
 
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|
 
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* Returns three elements named by the key of the map, and with the entries as concatenated text node.
 
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<syntaxhighlight lang="xquery">
 
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let $map := map { 'a': (), 'b': 2, 'c': [ 3, 4 ] }
 
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for $entry in util:map-entries($map)
 
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return element { $entry?key } { string-join($entry?value) }
 
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</syntaxhighlight>
 
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|}
 
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==util:map-values==
 
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{| width='100%'
 
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|- valign="top"
 
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| width='120' | '''Signature'''
 
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|<pre>util:map-values(
 
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  $map  as map(*)
 
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) as item()*</pre>
 
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|- valign="top"
 
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| '''Summary'''
 
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|Returns all values of a {{Code|$map}} as a sequence. Equivalent to:
 
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<syntaxhighlight lang="xquery">
 
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$map ? *
 
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</syntaxhighlight>
 
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|- valign="top"
 
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| '''Examples'''
 
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|
 
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* Returns the map values as two items:
 
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<syntaxhighlight lang="xquery">
 
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let $map := map { 'a': (), 'b': 2, 'c': [ 3, 4 ] }
 
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return util:map-values($map)
 
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</syntaxhighlight>
 
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|}
 
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=Helper Functions=
 
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==util:replicate==
 
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{| width='100%'
 
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|- valign="top"
 
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| width='120' | '''Signature'''
 
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|<pre>util:replicate(
 
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  $input  as item()*,
 
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  $count  as xs:integer,
 
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  $repeat  as xs:boolean?  := false()
 
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) as item()*</pre>
 
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|- valign="top"
 
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| '''Summary'''
 
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|Evaluates {{Code|$input}} and returns the result {{Code|$count}} times. Unless {{Code|$repeat}} is set to true, the input expression is evaluated multiple times. Equivalent expressions:
 
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<syntaxhighlight lang="xquery">
 
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util:replicate($input, $count, true()),
 
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(1 to $count) ! $input
 
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</syntaxhighlight>
 
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|- valign="top"
 
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| '''Errors'''
 
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|{{Error|negative|#Errors}} The specified number is negative.
 
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|- valign="top"
 
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| '''Examples'''
 
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|
 
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* <code>util:replicate('A', 3)</code> returns <code>A A A</code>.
 
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* In the following query, a single new element node is constructed, and {{Code|true}} is returned:
 
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<syntaxhighlight lang="xquery">
 
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let $nodes := util:replicate(<node/>, 2)
 
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return $nodes[1] is $nodes[2]
 
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</syntaxhighlight>
 
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* In this query, two nodes are constructed, and the result is {{Code|false}}:
 
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<syntaxhighlight lang="xquery">
 
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let $nodes := util:replicate(<node/>, 2, true())
 
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return $nodes[1] is $nodes[2]
 
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</syntaxhighlight>
 
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|}
 
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==util:duplicates==
 
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{| width='100%'
 
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|- valign="top"
 
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| width='120' | '''Signature'''
 
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|<pre>util:duplicates(
 
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  $sequence  as item()*,
 
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  $collation  as xs:string  := ()
 
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) as xs:anyAtomicType*</pre>
 
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|- valign="top"
 
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| '''Summary'''
 
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|Returns duplicate values in a {{Code|$sequence}}. See [https://www.w3.org/TR/xpath-functions-31/#func-distinct-values fn:distinct-values] for the applied equality rules and the usage of the {{Code|$collation}} argument.
 
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|- valign="top"
 
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| '''Examples'''
 
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|
 
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* <code>util:duplicates((1, 2, 1, 1))</code> returns <code>1</code>.
 
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|}
 
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==util:chars==
 
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{| width='100%'
 
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|- valign="top"
 
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| width='120' | '''Signature'''
 
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|<pre>util:chars(
 
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  $string  as xs:string?
 
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) as xs:string*</pre>
 
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|- valign="top"
 
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| '''Summary'''
 
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|Returns all characters of a {{Code|$string}} as a sequence. Equivalent to:
 
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<syntaxhighlight lang="xquery">
 
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for $cp in string-to-codepoints($string)
 
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return codepoints-to-string($cp)
 
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</syntaxhighlight>
 
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|- valign="top"
 
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| '''Examples'''
 
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|
 
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* <code>util:chars('AB')</code> returns the two strings <code>A</code> and <code>B</code>.
 
 
|}
 
|}
  

Revision as of 12:58, 26 October 2023

This XQuery Module contains some utility and helper functions.

With Version 11, many functions of this module have been removed as they are now part of the official specification:

BaseX 10 XQuery 4
util:array-members array:members
util:array-values array:values
util:chars fn:characters
util:duplicates fn:duplicate-values
util:init fn:trunk
util:intersperse fn:intersperse
util:item fn:items-at
util:last fn:foot
util:map-entries map:pairs
util:map-values map:values
util:replicate fn:replicate

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:count-within

Signature 
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:range

Signature 
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.

Node Functions

util:ddo

Signature 
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

Signature 
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

Signature 
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>

Errors

Code Description
negative The specified number is negative.

Changelog

Version 11.0
  • Removed: util:array-members, util:array-values, util:chars, util:duplicates, util:init, util:intersperse, util:item, util:last, util:map-entries, util:map-values, util:replicate
Version 9.7
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.

Retrieved from "http://docs.basex.org/index.php?title=Utility_Module&oldid=16674"