From: Mark Davis (firstname.lastname@example.org)
Date: Sat Oct 13 2007 - 12:29:16 CDT
The complement operation is only discussed in UTS #18 with regard to
character classes, not as a general operation. If you feel the text is
unclear on that point, perhaps you can look it over and suggest where it
could be enhanced. You can file this via the reporting form.
On 10/13/07, Hans Aberg <email@example.com> wrote:
> On 10 Oct 2007, at 19:38, Mark Davis wrote:
> > Andy and I put together a paper of recommendations for the UTC at
> > http://docs.google.com/Doc?id=dfqr8rd5_32kv97tx .
> I suspect you will run into problems when mixing complement with the
> Kleene closure (zero or more concatenations) operator (and other
> operators generating an infinite number of strings in the associated
> So one safe way is to admit the usual set operations on character
> classes only, and letting regular expressions having only the usual
> operators acting on character classes.
> If you don't use such infinite generating operators, the restriction
> forms a graded algebra, and it seems me you want the complement with
> respect to the grading (length of strings) in the generated language.
> Hans Åberg
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