🚀 go-pugleaf

In article <4648@undis.cs.chalmers.se>, jeffrey@cs.chalmers.se (Alan Jeffrey) writes:
> In article <1991May28.070140.16324@neon.Stanford.EDU> espie@ibis.Stanford.EDU (Marc Espie) writes:
>>So, now redefining !thing! to act like \mbox{thing} is not really 
>>difficult. Here is a quick answer, it should work with little or no
>>modification.
 
> Except that this will produce strange results for writers with a
> tendency to use exclaimation marks in their text!
 
> You could try
 
> \newtoks\everytext
> \newtoks\everyendtext
> \def\textshriek{!}
> \catcode`\!=\active
> \def!{\relax\ifmmode\expandafter\mathshriek\else\textshriek\fi}
> \def\mathshriek#1!{\hbox{\the\everytext#1\the\everyendtext}}
 
> This also gives you token lists \everytext and \everyendtext, which
> are used at the beginning and end of every !...! pair.  For example,
> if you want all of this text to be set in the upright font, with a
> quad space before and after, you could say

Alternatively, assign ! a mathcode of "8000. See p.155 of the
TeXbook for details (so am I the only one who knew about this
feature?)

> Exercise for the interested reader: why the \relax and why the
> \expandafter?  (The answers to these questions, as with any other you
> may have about life, the universe and everything, are kept within the
> covers of the TeXbook.)

Hmm, I don't think I've ever seen this use of \expandafter
before. I've more typically said:

\ifwhatever \let\next=\a\else\let\next=\b\fi \next

it still has uses but your technique is quite slick.

-dh
 
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