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Date:         Mon, 24 Aug 2015 07:30:53 +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 01:33, aparsloe wrote:
> It has taken me a while to get to grips with \tl_set_rescan:Nnn <tl var>
> {setup} {tokens}, not least the fact that *omission* from the setup
> means "revert to usual catcode". I think this is worth documenting in
> interface3.pdf, since it seems not unreasonable (at least it did to me)
> to suppose that if one has explicitly changed a catcode using
> \tl_set_rescan:Nnn, only a similarly explicit change would revert the
> catcode to its usual value. In particular it would be helpful to
> document the fact that using an empty setup { } reverts everything to
> usual values.
> 
> Andrew

I see what you mean: I'll add a note that any chars not set up
explicitly will have the *current* catcode applied. (That's not quite
the same as saying the 'usual' value.)

Worth noting perhaps that rescanning tokens is in general a bit tricky
to use safely. (Certainly if possible I find other ways of solving
problems.)
--
Joseph Wright