# [OS X TeX] Gobble left

Peter Pagin peter.pagin at philosophy.su.se
Thu Apr 21 15:35:46 EDT 2005

Thanks, Jonathan and Morten.
I'll have to try something else.

Best,
Peter

Morten Høgholm wrote:

> On Fri, 15 Apr 2005 08:22:28 +0200, Peter Pagin
> <peter.pagin at philosophy.su.se> wrote:
>
>> Hi, all.
>> Here's a TeX question, I guess. By means of
>>
>> \def\gobble #1{}
>>
>> a command \gobble is defined that deletes the next character (or
>> space)  to the right, or replaces it by whatever one puts between the
>> curly  brackets in the definition. My question is whether there is a
>> method for  doing the same to the character to the left, i.e.
>> preceding the  occurrence of the command.
>
>
> You can sometimes investigate what came right before your command and
> base  future actions on it but you can only remove a kern, skip or
> penalty.
>
> Some languages require this ability in order to do fully automated
> typesetting so it is something that'd be nice to have. However it
> would  require the engine to determine which character came before it
> and if it  was part of a ligature or not etc. and I doubt it's
> possible to implement  in the TeX engine - Jonathan can probably
> comment on this.

--
Peter Pagin
Professor
Department of Philosophy, Stockholm University
106 91 Stockholm, Sweden
tel: +46-8-162813, fax: +46-8-152226
email: peter.pagin at philosophy.su.se

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