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Heiko Oberdiek <[log in to unmask]>
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Mailing list for the LaTeX3 project <[log in to unmask]>
Thu, 10 Nov 2005 11:09:46 +0100
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On Thu, Nov 10, 2005 at 09:03:16AM +0100, Uwe Lück wrote:

> Hello,
> 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 what kind of object is the return value of \lastchar?
A number is quite useless, because this misses the font property.

Yours sincerely
  Heiko <[log in to unmask]>