Special Edition Using XSLT

Positional Predicates

As well as Boolean expressions, predicates can contain numerical expressions.

foo[5] 
foo[last()] 

These predicates match elements based on their document order in the node set.

Imagine this source document:

<person> 
    <name>Mr. Fish</name> 
    <address>The Sea</address> 
    <appearance>Shiny and scaly</appearance> 
<person> 

This expression produces a node set with three element nodes:

/person/* 

You can use a positional predicate on that node set to pull out the second node within it in document order:

/person/*[2] 

The result will be a node set containing just one node, the element <address>.

A more complex example would be to select the first <img> element in an XHTML document:

//img[1] 

The expression //img matches all