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Message-ID:  <4E9B4660.8020900@morningstar2.co.uk>
Date:         Sun, 16 Oct 2011 22:02:24 +0100
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From: Joseph Wright <joseph.wright@MORNINGSTAR2.CO.UK>
Subject: Re: Strings, and regular expressions
To: LATEX-L@listserv.uni-heidelberg.de
In-Reply-To:  <CANQYN6xiwms0LdCgW-6AQ9Pok9qbtc6k0ZgN40z6RK9+a=RdWg@mail.gmail.com>
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Status: R

On 10/10/2011 16:07, Bruno Le Floch wrote:
> The l3regex module allows for testing if a string matches a given
> regular expression, counting matches, extracting submatches, splitting
> at occurrences of a regular expression, and doing replacement (see
> documentation for function names).

I'm not sure about the approach on submatches. You say

% Submatches with numbers higher than $10$ are accessed in the same way,
% namely |\10|, |\11|, \emph{etc}. To insert in the replacement text
% a submatch followed by a digit, the digit must be entered using the
% |\x| escape sequence: for instance, to get the first submatch followed
% by the digit $7$, use |\1\x37|, because $7$ has character code |37|
% (in hexadecimal).

I wonder how likely it is that we'll need more than 9 submatches in the
sort of scenario that l3regex is likely to applied in. TeX programmers
are already used to the idea that we have up to 9 numbered parameters,
so why not limit to nine submatches and avoid the need to use "\x" syntax?

I wonder if \regex_set:Nn would be better as \regex_save:Nn. My
reasoning is that \<var>_set:Nn functions are used with a variable of
name \l_..._<var>, while here we are (currently) naming as \l_..._tl.
-- 
Joseph Wright