RE: check the type of the $pattern argument to a regul

> This is one way to way check if a pattern is valid:
> 
> <xsl:stylesheet version="2.0"
> 	xmlns:regex="java.util.regex.Pattern"
> 	xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
> 	xmlns:saxon="http://saxon.sf.net/">
> 
> <xsl:template match="/">
> 	<xsl:value-of select="saxon:try(regex:compile(']['), 
> 'false')"/> </xsl:template>
> 
> </xsl:stylesheet>
> 
> This attempts to compile the regex using Java, and catches 
> the PatternSyntaxException using Saxon SA's saxon:try() 
> function.  In this case it returns "false" because "][" is invalid.

Java regular expressions and XPath regular expressions are not the same
thing!

Michael Kay
http://www.saxonica.com/