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Message-ID:  <19886.1152.703662.453176@morse.mittelbach-online.de>
Date:         Tue, 19 Apr 2011 23:54:08 +0200
Reply-To: Mailing list for the LaTeX3 project
              <LATEX-L@listserv.uni-heidelberg.de>
Sender: Mailing list for the LaTeX3 project <LATEX-L@listserv.uni-heidelberg.de>
From: Frank Mittelbach <frank.mittelbach@LATEX-PROJECT.ORG>
Subject: Re: The nature of popping from an empty sequence
To: LATEX-L@listserv.uni-heidelberg.de
In-Reply-To:  <4DAE0235.1020602@morningstar2.co.uk>
Precedence: list
Status: R

Joseph Wright writes:
 > On 19/04/2011 22:36, Frank Mittelbach wrote:
 > > Bruno Le Floch writes:
 > >  > > Within xtemplate, you'll find some places where we use the fact that the
 > >  > > keys do have catcodes to pull off some 'special effects'. Now, we also
 > >  > > remove spaces there, so spaces can also be used for said 'special
 > >  > > effects'. But such a change would require some alterations.
 > >  > 
 > >  > Ok, so my assumption was wrong. But really, playing with catcodes is evil
 > >  > ;-).
 > > 
 > > right and that was a fairly recent change in implementation, wasn't it. It
 > > might be worth while rethinking if we limit the nature of keys and their
 > > comparison even if we have to modify the xtemplate code for it
 > 
 > I'd have to check the detail, but from memory this was the most
 > convenient way to store the key order within the template itself. There
 > is nothing to stop us moving it back out again to a dedicated location.

I'm not claiming that the change to a restricted key set as suggested is the
"right thing" to do, but I agree with Bruno's sentiment on the evility :-) of
catcodes and thereis something to say for restricting "keys" to be string-like
objects, ie behaving like they "look".

frank