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Message-ID:  <55DC579E.30808@morningstar2.co.uk>
Date:         Tue, 25 Aug 2015 12:55:10 +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 25/08/2015 12:49, Bruno Le Floch wrote:
>> I guess I'd want to know a bit more about use cases. As I've said on
>> LaTeX-L, normally brace groups are an 'escape' mechanism from the
>> scanner, so I'm not sure I'd expect recursive replacement as a general
>> thing. I'm wondering if this is being used for something rather 'text
>> like', which might be handled by l3regex (slow but for a smaller number
>> of cases reasonable).
> 
> I'm not completely sure that l3regex will be slower in all cases than
> an approach based on my nested mappings.  Besides, if we find some
> common use-cases of regexes that can be optimized, I can work on that.
> For instance, I saw someone use \c{alpha}|\c{beta}|..., which is
> currently quite slow but can be optimized.

I'll take your word for it on performance! I think it's not a bad thing
to say \tl_replace_all:Nnn is fast(ish) but 'simple', l3regex is slower
but can 'everything' and avoid a proliferation of search-and-replace
functions.

Joseph