Re: [xsl] check the type of the $pattern argument to a regular expression?

[Abel Braaksma <abel.online@xxxxxxxxx>]

Andrew Welch wrote:
> 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.

Nice one! But note that there are quite some differences between Java 
regexes and XSLT regexes. You may be able to compile regexes that are 
valid in Java (i.e., matching emptiness, but there are also some 
syntactic differences), but not valid in XSLT.

Cheers,
-- Abel Braaksma