Utility Module

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

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 $default. The function is equivalent to one of the following expressions: if(exists($items)) then $items else $default $items ?: $default (see Elvis Operator for more details)
Examples	util:or(123, 456) returns 123. util:or(1[. = 0], -1) returns -1.

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

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

util:last

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

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

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

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

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

• Added: util:if, util:or

Version 9.0

• Added: util:replicate

The Module was introduced with Version 8.5.