goxml / goxpath / goxslt

Instructions

xsl:function

Defines a custom XPath function callable from any XPath expression in the stylesheet.

<xsl:function name="my:double" as="xs:integer"
    xmlns:my="http://example.com/my">
  <xsl:param name="n" as="xs:integer"/>
  <xsl:sequence select="$n * 2"/>
</xsl:function>

The function name must be a QName in a non-XSLT, non-built-in namespace. Each xsl:param declares one positional parameter; functions don’t have default values, so all parameters are required. The body is a sequence constructor whose result is returned. Use xsl:sequence (rather than xsl:value-of) to return typed values rather than text nodes.

Functions can be overloaded by arity: two xsl:function declarations with the same name but a different number of parameters are distinct functions.

Attributes

Attribute	Description
`name`	QName of the function. Required.
`as`	Sequence type of the return value.
`override-extension-function`	`yes` or `no`.
`visibility`	Visibility for package mode (`public`, `private`, …).

Examples

Recursive factorial:

<xsl:function name="my:fact" as="xs:integer"
    xmlns:my="http://example.com/my">
  <xsl:param name="n" as="xs:integer"/>
  <xsl:sequence select="
    if ($n &lt;= 1) then 1
    else $n * my:fact($n - 1)"/>
</xsl:function>

<!-- Usage: -->
<xsl:value-of select="my:fact(5)"/>  <!-- 120 -->

Two arities:

<xsl:function name="my:greet">
  <xsl:param name="who"/>
  <xsl:sequence select="my:greet($who, 'Hello')"/>
</xsl:function>

<xsl:function name="my:greet">
  <xsl:param name="who"/>
  <xsl:param name="word"/>
  <xsl:sequence select="concat($word, ', ', $who, '!')"/>
</xsl:function>

xsl:for-each-group xsl:if