XSLT Cookbook

Making Do Without Regular Expressions

Problem

You would like to perform regular-expression-like operations but you don’t want to resort to nonstandard extensions.

Solution

Several common regular-expression-like matches can be emulated in native XSLT. Table 1-1 lists the regular-expression matches by using Perl syntax along with their XSLT/XPath equivalent. The single character “C” is a proxy for any user-specified single character, and the string “abc” is a proxy for any user supplied-string of nonzero length.

Table 1-1. Regular-expression matches

$string =~ /^C*$/	translate($string,'C','') = ''
$string =~ /^C+$/	$string and translate($string,'C', '') = ''
$string =~ /C+/	contains($string,'C')
$string =~ /C{2,4}/	contains($string,'CC') and not(contains($string,'CCCCC'))
$string =~ /^abc/	starts-with($string,'abc')
$string =~ /abc$/	substring($string, string-length($string) - string-length('abc') + 1) = 'abc'
$string =~ /abc/	contains($string,'abc')
$string =~ /^[^C]*$/	translate($string,'C','') = $string
$string =~ /^\s$/	not(normalize-space($string))
$string =~ /\s/	translate(normalize-space($string),' ','') != $string
$string =~ /^\S$/	translate(normalize-space($string),' ','') = $string

Discussion

When it comes to brevity and power, nothing beats a good regular-expression engine. However, many simple matching operations can be emulated by more cumbersome yet effective XPath expressions. Many of these matches are facilitated by translate( ), which removes ...