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Date:         Thu, 27 Aug 2015 21:18:58 +0100
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From: Joseph Wright <joseph.wright@MORNINGSTAR2.CO.UK>
Subject: Re: Catcode changes
To: LATEX-L@LISTSERV.UNI-HEIDELBERG.DE
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Status: R

On 27/08/2015 19:09, Joseph Wright wrote:
> On 27/08/2015 18:28, Lars Hellström wrote:
>> Bruno Le Floch skrev 2015-08-27 12.34:
>>> That's much harder.  Catcode changes are probably warranted in this
>>> case, since teaching TeX to nest parentheses in this way is tough.
>>
>> I seem to recall that I did demonstrate how to do that -- have TeX match
>> parentheses in an expression, using delimited arguments rather than
>> catcode changes -- in a mail to this very list several years ago... Yes,
>> it was on 2011-10-19 and the subject was "Re: Church booleans".
> 
> We do the same in xparse :-)
> 
>> PS: I maintain that that approach to evaluating infix boolean
>> expressions is far superior to what is currently offered in LaTeX3, but
>> Bruno just seems to *love* his &&, with all its shortcomings. ;-)
> 
> Will remind myself: as has been noted there is an issue with clearing up
> certain tokens with the current lazy evaluation method.
> 
> Joseph
> 

BTW, thread you mean starts

  http://article.gmane.org/gmane.comp.tex.latex.latex3/2719

I think the one you mean is

  http://article.gmane.org/gmane.comp.tex.latex.latex3/2754

Joseph

P.S. Boolean expressions are Morten's code, not Bruno's :-)