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New functions in 2.0 / 3.0 / 3.1

This page is a reference and refresher, not the next required step in the linear tutorial. Read it straight through when surveying what changed, or return to it when an older XPath 1.0 idiom feels more complicated than it ought to be. The conceptual chapters link to the larger additions—regular expressions, maps, arrays, JSON, and higher-order functions—in context.

The 1.0 function library is small — count, string, concat, substring, translate, and a handful more. Every version since has added to it. The big additions get their own pages (regex, dates, higher-order, maps & arrays, JSON, text I/O); this page is a reference for the smaller but constantly-useful functions that don't each need a chapter.

The version column is when the function appeared (2.0, 3.0, 3.1). All of these work in the free Saxon-HE.

Working with sequences

Function Does Ver
distinct-values($seq) drop duplicate atomic values 2.0
index-of($seq, $v) positions where $v occurs 2.0
subsequence($seq, $start [, $len]) a slice, 1-based 2.0
reverse($seq) reverse order 2.0
insert-before / remove($seq, $pos …) add / drop items by position 2.0
head($seq) / tail($seq) first item / everything-but-first 3.0
exists($seq) / empty($seq) is the sequence non-empty / empty 2.0
deep-equal($a, $b) recursive value+structure equality 2.0 
<xsl:value-of select="distinct-values(/catalog/cd/@genre)"/>   <!-- country pop rock -->
<xsl:value-of select="head(/catalog/cd)/title"/>               <!-- Empire Burlesque -->

Aggregates and numbers

Function Does Ver
avg($seq) / min($seq) / max($seq) average / smallest / largest 2.0
abs($n) absolute value 2.0
round-half-to-even($n [, $p]) banker's rounding 2.0
format-integer($n, $picture) 1 → i, one, 001, … 3.0
random-number-generator([$seed]) a map yielding pseudo-random numbers 3.1 
<xsl:value-of select="avg(/catalog/cd/xs:decimal(price))"/>    <!-- 10.233… -->
<xsl:value-of select="format-integer(4, 'I')"/>                <!-- IV -->

Strings

Most string work lives on the regex & strings page; the essentials:

Function Does Ver
string-join($seq [, $sep]) concatenate with a separator 2.0
upper-case / lower-case($s) case conversion 2.0
normalize-unicode($s) Unicode normalisation (NFC, …) 2.0
string-to-codepoints / codepoints-to-string string ⇄ code points 2.0
tokenize / replace / matches see regex 2.0

Nodes and documents

Function Does Ver
doc($uri) / doc-available($uri) load an XML document / test it loads 2.0
collection($uri) / uri-collection($uri) a set of documents / their URIs 2.0 / 3.0
path($node) the node's XPath location, as a string 3.0
has-children($node) does it have child nodes 3.0
innermost($seq) / outermost($seq) strip ancestors / descendants from a node set 3.0
unparsed-text / parse-xml / serialize text & string I/O 2.0 / 3.0 
<xsl:if test="doc-available('prices.xml')">
  <xsl:value-of select="doc('prices.xml')/prices/total"/>
</xsl:if>

Diagnostics

Function Does Ver
trace($value, $label) log $value to the processor's trace output, return it unchanged 2.0
error([$code [, $desc]]) abort with an error — see error handling 2.0

trace is the printf-debugging of XSLT: wrap any sub-expression in it and watch what flows through without altering the result.

The bigger additions (their own pages)

For completeness, the major library growth covered elsewhere:

  • Regex & strings — tokenize, replace, matches → regex
  • Dates — format-date, current-dateTime, the *-from-* accessors → dates and times
  • Higher-order — for-each, filter, fold-left/-right, sort, apply → higher-order functions
  • Maps & arrays — the map:* and array:* namespaces → maps and arrays
  • JSON — parse-json, json-doc, json-to-xml, xml-to-json → JSON

Where to go next