Difference between revisions of "Utility Module"
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=Conventions= | =Conventions= | ||
− | All functions in this module and errors are assigned to the <code><nowiki>http://basex.org/modules/util</nowiki></code> namespace, which is statically bound to the {{Code|util}} prefix.<br/> | + | All functions and errors in this module and errors are assigned to the <code><nowiki>http://basex.org/modules/util</nowiki></code> namespace, which is statically bound to the {{Code|util}} prefix.<br/> |
− | = | + | =Conditions= |
− | ==util: | + | ==util:if== |
{| width='100%' | {| width='100%' | ||
|- | |- | ||
| width='120' | '''Signatures''' | | width='120' | '''Signatures''' | ||
− | |{{Func|util:item- | + | |{{Func|util:if|$condition as item()*, $then as item()*|item()*}}<br/>{{Func|util:if|$condition as item()*, $then as item()*, $else as item()*|item()*}}<br/> |
+ | |- | ||
+ | | '''Summary''' | ||
+ | |Alternative writing for the if/then/else expression: | ||
+ | * If the ''effective boolean value'' of {{Code|$condition}} is true, the {{Code|$then}} branch will be evaluated. | ||
+ | * Otherwise, {{Code|$else}} will be evaluated. If no third argument is supplied, an empty sequence will be returned. | ||
+ | |- | ||
+ | | '''Examples''' | ||
+ | | | ||
+ | * <code>util:if(true(), 123, 456)</code> returns {{Code|123}}. | ||
+ | * <code>util:if(0, 'wrong!')</code> returns an empty sequence. | ||
+ | |} | ||
+ | |||
+ | ==util:or== | ||
+ | |||
+ | {| width='100%' | ||
+ | |- | ||
+ | | width='120' | '''Signatures''' | ||
+ | |{{Func|util:or|$items as item()*, $default as item()*|item()*}} | ||
+ | |- | ||
+ | | '''Summary''' | ||
+ | |Returns {{Code|$items}} if it is a non-empty sequence. Otherwise, returns {{Code|$default}}. The function is equivalent to one of the following expressions: | ||
+ | * <code>if(exists($items)) then $items else $default</code> | ||
+ | * <code>$items ?: $default</code> (see [[XQuery Extensions#Elvis Operator|Elvis Operator]] for more details) | ||
+ | |- | ||
+ | | '''Examples''' | ||
+ | | | ||
+ | * <code>util:or(123, 456)</code> returns {{Code|123}}. | ||
+ | * <code>util:or(1[. = 0], -1)</code> returns {{Code|-1}}. | ||
+ | |} | ||
+ | |||
+ | =Positional Access= | ||
+ | |||
+ | ==util:item== | ||
+ | |||
+ | {| width='100%' | ||
+ | |- | ||
+ | | width='120' | '''Signatures''' | ||
+ | |{{Func|util:item|$sequence as item()*, $position as xs:double|item()?}}<br/> | ||
|- | |- | ||
| '''Summary''' | | '''Summary''' | ||
Line 19: | Line 57: | ||
| '''Examples''' | | '''Examples''' | ||
| | | | ||
− | * <code>util:item | + | * <code>util:item(reverse(1 to 5), 1)</code> returns <code>5</code>. |
− | * <code>util:item | + | * <code>util:item(('a','b'), 0)</code> returns an empty sequence. |
|} | |} | ||
− | ==util: | + | ==util:range== |
{| width='100%' | {| width='100%' | ||
|- | |- | ||
| width='120' | '''Signatures''' | | width='120' | '''Signatures''' | ||
− | |{{Func|util: | + | |{{Func|util:range|$sequence as item()*, $first as xs:double, $last as xs:double|item()*}}<br/> |
|- | |- | ||
| '''Summary''' | | '''Summary''' | ||
Line 35: | Line 73: | ||
| '''Examples''' | | '''Examples''' | ||
| | | | ||
− | * <code>util: | + | * <code>util:range(//item, 11, 20)</code> returns all path results from (if available) position 11 to 20. |
|} | |} | ||
− | ==util:last | + | ==util:last== |
{| width='100%' | {| width='100%' | ||
|- | |- | ||
| width='120' | '''Signatures''' | | width='120' | '''Signatures''' | ||
− | |{{Func|util:last | + | |{{Func|util:last|$sequence as item()*|item()?}}<br/> |
|- | |- | ||
| '''Summary''' | | '''Summary''' | ||
Line 50: | Line 88: | ||
| '''Examples''' | | '''Examples''' | ||
| | | | ||
− | * <code>util:last | + | * <code>util:last(reverse(1 to 100))</code> returns <code>1</code>. |
+ | |} | ||
+ | |||
+ | ==util:init== | ||
+ | |||
+ | {| width='100%' | ||
+ | |- | ||
+ | | width='120' | '''Signatures''' | ||
+ | |{{Func|util:init|$sequence as item()*|item()*}}<br/> | ||
+ | |- | ||
+ | | '''Summary''' | ||
+ | |Returns all items of a {{Code|$sequence}} except for the last one. Equivalent to <code>$sequence[position() < last()]</code>. | ||
+ | |- | ||
+ | | '''Examples''' | ||
+ | | | ||
+ | * <code>util:init(1 to 4)</code> returns <code>1 2 3</code>. | ||
+ | |} | ||
+ | |||
+ | =Helper Functions= | ||
+ | |||
+ | ==util:replicate== | ||
+ | |||
+ | {| width='100%' | ||
+ | |- | ||
+ | | width='120' | '''Signatures''' | ||
+ | |{{Func|util:replicate|$sequence as item()*, $count as xs:integer|item()*}}<br/> | ||
+ | |- | ||
+ | | '''Summary''' | ||
+ | |Returns {{Code|$count}} instances of the specified {{Code|$sequence}}. A similar result can be generated with <code>(1 to $count) ! $sequence</code>, but in the latter case, the right-hand expression will be evaluated multiple times. | ||
+ | |- | ||
+ | | '''Errors''' | ||
+ | |{{Error|negative|#Errors}} The specified number is negative. | ||
+ | |- | ||
+ | | '''Examples''' | ||
+ | | | ||
+ | * <code>util:replicate('A', 3)</code> returns <code>A A A</code>. | ||
+ | |} | ||
+ | |||
+ | ==util:chars== | ||
+ | |||
+ | {| width='100%' | ||
+ | |- | ||
+ | | width='120' | '''Signatures''' | ||
+ | |{{Func|util:chars|$string as xs:string|xs:string*}}<br/> | ||
+ | |- | ||
+ | | '''Summary''' | ||
+ | |Returns all characters of a {{Code|$string}} as a sequence. Equivalent to <code>string-to-codepoints($string) ! codepoints-to-string(.)</code>. | ||
+ | |- | ||
+ | | '''Examples''' | ||
+ | | | ||
+ | * <code>util:chars('AB')</code> returns the two strings <code>A</code> and <code>B</code>. | ||
+ | |} | ||
+ | |||
+ | ==util:ddo== | ||
+ | |||
+ | {{Mark|Introduced with Version 9.3:}} | ||
+ | |||
+ | {| width='100%' | ||
+ | |- | ||
+ | | width='120' | '''Signatures''' | ||
+ | |{{Func|util:ddo|$nodes as node()*|node()*}}<br/> | ||
+ | |- | ||
+ | | '''Summary''' | ||
+ | |Returns nodes in ''distinct document order'': duplicate nodes will be removed, and the remaining nodes will be returned in [https://www.w3.org/TR/xquery-31/#dt-document-order document order]. All results of path expression are in distinct document order, so the function is equivalent to the expression <code>$nodes/self::node()</code>. | ||
+ | |} | ||
+ | |||
+ | =Errors= | ||
+ | |||
+ | {| class="wikitable" width="100%" | ||
+ | ! width="110"|Code | ||
+ | |Description | ||
+ | |- | ||
+ | |{{Code|negative}} | ||
+ | |The specified number is negative. | ||
|} | |} | ||
=Changelog= | =Changelog= | ||
+ | |||
+ | ;Version 9.3 | ||
+ | * Added: [[#util:ddo|util:ddo]] | ||
+ | |||
+ | ;Version 9.2 | ||
+ | * Added: [[#util:chars|util:chars]], [[#util:init|util:init]] | ||
+ | * Updates: [[#util:item|util:item]], [[#util:last|util:last]], [[#util:range|util:range]] renamed (before: {{Code|util:item-at}}, {{Code|util:item-range}}, {{Code|util:last-from}}) | ||
+ | |||
+ | ;Version 9.1 | ||
+ | * Added: [[#util:if|util:if]], [[#util:or|util:or]] | ||
+ | |||
+ | ;Version 9.0 | ||
+ | * Added: [[#util:replicate|util:replicate]] | ||
The Module was introduced with Version 8.5. | The Module was introduced with Version 8.5. |
Revision as of 06:54, 29 November 2019
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 $default . The function is equivalent to one of the following expressions:
|
Examples |
|
Positional Access
util:item
Signatures | util:item($sequence as item()*, $position as xs:double) as item()? |
Summary | Returns the item from $sequence at the specified $position . Equivalent to $sequence[$position] .
|
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 $last . Equivalent to subsequence($sequence, $first, $last - $first + 1) .
|
Examples |
|
util:last
Signatures | util:last($sequence as item()*) as item()? |
Summary | Returns last item of a $sequence . Equivalent to $sequence[last()] .
|
Examples |
|
util:init
Signatures | util:init($sequence as item()*) as item()* |
Summary | Returns all items of a $sequence except for the last one. Equivalent to $sequence[position() < last()] .
|
Examples |
|
Helper Functions
util:replicate
Signatures | util:replicate($sequence as item()*, $count as xs:integer) as item()* |
Summary | Returns $count instances of the specified $sequence . A similar result can be generated with (1 to $count) ! $sequence , but in the latter case, the right-hand expression will be evaluated multiple times.
|
Errors | negative : The specified number is negative.
|
Examples |
|
util:chars
Signatures | util:chars($string as xs:string) as xs:string* |
Summary | Returns all characters of a $string as a sequence. Equivalent to string-to-codepoints($string) ! codepoints-to-string(.) .
|
Examples |
|
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. All results of path expression are in distinct document order, so the function is equivalent to the expression $nodes/self::node() .
|
Errors
Code | Description |
---|---|
negative
|
The specified number is negative. |
Changelog
- Version 9.3
- Added: util:ddo
- Version 9.2
- Added: util:chars, util:init
- Updates: 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.