[TUHS] GNU eqn clarifications and reforms

G. Branden Robinson g.branden.robinson at gmail.com
Sat Jun 17 05:38:57 AEST 2023

At 2023-06-17T05:19:46+1000, Damian McGuckin wrote:
> Getting back to groff, that final/terminating sigma, is it still
> pronounced as sigma.
> It certainly has no EQN equivalent name and its groff short symbol
> name is
> 	\(ts
> (terminal sigma) which is not like other greek letters.  Just
> wondering whether it needs a sentence to mention its abscence from
> EQN.

There are a few others, but they postdate Ossanna troff.  From
groff_char(7) in 1.23.0.rc4:

    ϵ        \[+e]   u03F5     variant epsilon (lunate)
    ϑ        \[+h]   u03D1     variant theta (cursive form)
    ϖ        \[+p]   u03D6     variant pi (similar to omega)
    φ        \[+f]   u03C6     variant phi (curly shape)
    ς        \[ts]   u03C2     terminal lowercase sigma +

I know of no reason to make these generally available by default in eqn,
though, any more than they already are.  You can type their special
characters in eqn input and assign spacing and style types to them.
(This typing system is a GNU eqn feature, not present in AT&T eqn).

In fact I have a coupled pair of reforms in mind for GNU eqn:
unfastening the definitions of the lowercase Greek special characters
from the typeface used for letters (variables), and then defining the
lowercase Greek letter eqn macro names ("alpha", "beta", ...) to
explicitly use the "letter" style type.


(For example:

define alpha ! type "letter" \(*a !


This should result in no change for historical documents (except on
terminals, where it will fix a bug), and give us some flexibility for
users of modern fonts where Greek letters are properly supported in text
fonts (i.e., in four styles).

The Graphic Systems C/A/T had uppercase Greek available _only_ upright
and lowercase Greek _only_ italic.  Modern typesetting systems are not
so limited.

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