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Date: Thu, 10 Nov 2005 09:03:16 +0100
Reply-To: Mailing list for the LaTeX3 project <[log in to unmask]>
From: Uwe Lück <[log in to unmask]>
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At 07:52 10.11.05, Will Robertson wrote:

>Finally, somehow the topic of extensions to pdf-e-TeX came up, and
>there were some naive comments from me and some interesting comments
>from Morten. I proposed the idea of something like \previouschar,
>which we interpreted in two separate ways:
>  - it "would return the slot number of the most recently seen char
>or ligature node independently of whether we just saw a glue node or
>another char/lig node; any other node type could reset it to
>-1" [morten]
>  - it would actually be more like LaTeX's \@ifnextchar, and look at
>the input token list [me]
>Implicit in my thinking was that you could also eat up previous chars
>in the same was as \unskip with a sort of fine-grained \lastbox; to
>which idea Morten replied:
>   This is exactly what some languages need.
>   Since there are so many different node types the only safe
>   (IMO) way is to backtrack one node at a time so ideally we
>   would want the pair \lastchar and \unchar. And then we might
>   as well get one for each different node type. I guess someone
>   has to come up with a good idea about what to do with \discretionary
>   because I'm not at all sure what the semantics should be.

by accident, this occurred to me as well, if only for a
rather fun application. \lastchar and \unchar are perfect.

   Uwe Lück.