[texhax] making underscore a letter
Philip Taylor (Webmaster)
P.Taylor at Rhul.Ac.Uk
Thu Apr 19 15:15:11 CEST 2007
Morten Høgholm wrote:
> The usual trouble of trying to change catcodes on the fly: Once an
> argument is read, catcodes are locked and can't change, unless you go
> via \scantokens or a temporary file (which is what \scantokens is only
> much faster).
There is an alternative approach : use a tail-recursive
macro with a delimited parameter structure
(say \foo #1_#2\sentinel)
The first delimiter is "_" with its new catcode, and
the macro expands to yield
with the original catcode of "_". Tail recursion
is needed to cope with further "_"s in #2.
Suggested to DEK at TUG's tenth anniversary meeting.
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