Learning XSLT

Chapter 5. XPath and XSLT Functions

XPath defines 27 functions that may be called in expressions, including predicates. XSLT adds 9 functions to the XPath mix. You have already seen a number of these functions at work in previous examples in this book, such as name( ), string-length( ), and substring( ).

??? briefly documents all of the XPath 1.0 functions, including arguments. Similarly, ??? describes the XSLT 1.0 functions. XPath functions are divided into 4 types: Boolean, node-set, number, and string.

Tip

Node tests such as text( ) and comment( ) look like functions but they are not really functions. Node tests simply test whether a given node matches a node type.

I’ll demonstrate a number of functions in this chapter, but other chapters in this book will expose you to more examples of functions. For additional details on XPath functions, see Section 4 of the XPath specification. You can read more about XSLT functions in Sections 12 through 15 of the XSLT specification.

Tip

This is an introductory book and it does not provide exhaustive explanations of all of the XPath functions, though it will give you a chance to use many of them. John Simpson’s XPath and XPointer (O’Reilly) explores XPath (and its derivative XPointer) in greater detail. Doug Tidwell’s XSLT (O’Reilly), provides an excellent reference that demonstrates all these functions, as does Michael Kay’s XSLT Programmer’s Reference (Wrox). Another resource is Mulberry Technologies’ XSLT and XPath Quick Reference at