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Re: mathcode of non printable characters


> In plain.tex and consequently in lplain.tex there are \mathcode
> assignments for control-a (ASCII 1) and the like. A while ago I
> removed all these from lplain.tex (without someone noticing it, it
> seems). Is there any reason why these should remain?

The reason why they are there in the first place is that there
actually existed (do they still exist?) keyboards with special symbols
in the indicated positions.  Knuth used (and perhaps still does) such
a keyboard.  (See The TeXbook, pp. 135 and 369.)

Since I have never seen such a keyboard myself, I conclude that they
are not common.  So, in my opinion, you should not reintroduce these
assignments, at least not in lplain.tex, but perhaps in a style file
(if there is a demand for it).

> \mathcode`\ ="8000 % \space
> \mathcode`\'="8000 % ^\prime
> \mathcode`\_="8000 % \_
>
>
> I can see the reason for prime, but why the other two?

This is surely meant for some of Knuth's own esoteric macros?  I have
even looked through some of the most commonly available of Knuth's
files (plain.tex, manmac.tex, texbook.tex, and webmac.tex).  I didn't
find any constructions where the third definition has any effect.  The
first definition only makes a difference, if \obeyspaces is in force.

The second definition should of course be kept (otherwise most of my
files will look strange when printed :-).

---
Frank Jensen,   fj@iesd.auc.dk
Department of Mathematics and Computer Science
Aalborg University
DENMARK