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 :-)