I *think* David's point is that the problem is mathematically insoluble: the
grammar for regular expressions is recursive, and regular expressions are
not powerful enough to process a language whose grammar is recursive.

Sorry I suggested it!

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

> -----Original Message-----
> From: bryan rasmussen [mailto:rasmussen.bryan@xxxxxxxxx] 
> Sent: 15 April 2007 09:45
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject: Re:  check the type of the $pattern argument to 
> a regular expression?
> 
> I thought that was the most likely solution, although it 
> might be that one would want to break the task into a 
> template and a number of regular expressions, anyway I was 
> wondering if anyone knew of such a solution already?
> 
> cheers,
> Bryan Rasmussen
> 
> On 4/15/07, David Carlisle <davidc@xxxxxxxxx> wrote:
> >
> > > Short of writing a regular expression that only matches valid 
> > > regular expressions (which sounds like an interesting 
> exercise for 
> > > the reader),
> >
> > along with other interesting exercises like trisecting angles and 
> > squaring the circle, presumably:-)
> >
> > David