# [texhax] The details of \csname, in this specific case

Reinhard Kotucha reinhard.kotucha at web.de
Mon Feb 25 21:46:06 CET 2013

On 2013-02-25 at 19:35:22 +0100, Uwe Lück wrote:

> > 4) How exactly does TeX come to interpret the #1 as a "character
> > token," aren't things above value 127 by default labeled "invalid?"
>
> I guess the same, and I had to care for this in the fifinddo package
> by a loop turning the character codes into "other".
> Your code may work due to earlier context that does the same.
> I have seen such a loop in the graphics package. From a glance at
> inputenc.sty (LaTeX) I guess that it turns them into "active"
>
> I cannot find an answer in The TeXbook quickly about TeX's
> (INITEX's) default (would require reading many pages).
> AFAIK The TeXbook originally was written
> when TeX took 7-bit characters. I would not be surprised
> if the default were left to the installation.
> After what I have experienced and seen, I would say that
> it is safe (at least) to "fix" those catcodes before

\$ tex -ini \\relax
This is TeX, Version 3.1415926 (TeX Live 2012) (INITEX)

*\showthe\catcode 222
> 12.
<*> \showthe\catcode 222

describes TeX 3, which is an 8-bit engine.

Regards,
Reinhard

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Reinhard Kotucha                                      Phone: +49-511-3373112
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