Difference between revisions of "Utility Module"

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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.


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.



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:
  • 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.
  • util:if(true(), 123, 456) returns 123.
  • util:if(0, 'wrong!') returns an empty sequence.


Signatures util:or($items as item()*, $default as item()*) as item()*
Summary Returns $items if it is a non-empty sequence. Otherwise, returns $default. The function is equivalent to one of the following expressions:
  • if(exists($items)) then $items else $default
  • $items ?: $default (see Elvis Operator for more details)
  • util:or(123, 456) returns 123.
  • util:or(1[. = 0], -1) returns -1.

Positional Access


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].
  • util:item(reverse(1 to 5), 1) returns 5.
  • util:item(('a','b'), 0) returns an empty sequence.


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).
  • util:range(//item, 11, 20) returns all path results from (if available) position 11 to 20.


Signatures util:last($sequence as item()*) as item()?
Summary Returns last item of a $sequence. Equivalent to $sequence[last()].
  • util:last(reverse(1 to 100)) returns 1.


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()].
  • util:init(1 to 4) returns 1 2 3.

Helper Functions


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.
  • util:replicate('A', 3) returns A A A.


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(.).
  • util:chars('AB') returns the two strings A and B.


Introduced with Version 9.3:

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().


Code Description
negative The specified number is negative.


Version 9.3
Version 9.2
Version 9.1
Version 9.0

The Module was introduced with Version 8.5.