# math axis

• To: math-font-discuss@cogs.susx.ac.uk
• Subject: math axis
• From: J%org Knappen <Joerg.Knappen@uni-mainz.de>
• Date: Tue, 24 Aug 1993 21:47 +0200

I had a discussion with Justin today, and we discovered that there are
actually (at least) two different methods for TeX to put things onto the
math axis:

1) Glyphs are actually centered to the math axis. For this purpose, the
value of math_axis is extracted from \textfont3 (cmex10 usually). This
method is used for centering all big operators (i.e. an atom of type
mathop and containing only one character).

2) TeX expects, that the glyph is already adjusted to the math axis. This
is true e.g. for the minus sign. Since the value of math_axis is size
dependent, it only coincides at 10pt size with the one of cmex10. In
larger sizes, the two math axes are drifting apart!

Cure:

I don't know. TeX could overwrite the value of math_axis for \textfont3 if a
12pt style is choosen. Or \textfont3 can be made size-dependent (a choice
several people prefer for the reason, that the delimeters become bigger and
weightier).

--J"org Knappen.

P.S. Some major gateway seems to be down, since my mail volume has
decreased very much. I'll probably get a bit out of synch.