XSLT, 2nd Edition

[2.0] Constructor Functions

XPath 2.0 introduces the idea of constructor functions, which are similar to constructor functions in object-oriented languages. As with object-oriented languages, the name of the constructor function is the name of the datatype. Here’s how to create a value of type xs:date:

<xsl:variable name="birthday" select="xs:date('1995-04-21')"/>

This takes the string 1995-04-21 and creates a new value of type xs:date. This can cause runtime errors, as you would expect. A stylesheet that contains this instruction won’t run at all:

<xsl:variable name="birthday" select="xs:date('next Tuesday')"/>

This is a static error because the stylesheet processor knows this instruction will fail. On the other hand, we’ll get a runtime error if we send bad data to the xs:date constructor while the stylesheet is being processed:

<xsl:variable name="birthday" select="xs:date(@birthday)"/>

This uses the birthday attribute of the current node to create a new xs:date value. If that attribute contains a value that can be cast as a xs:date, everything is fine; if the attribute doesn’t contain valid data, we get a runtime error.