Re: GNU eqn clarifications and reforms (was: EQN - special words)

[G. Branden Robinson]

Hi Damian,

At 2023-06-12T17:31:11+1000, Damian McGuckin wrote:
> 
> Looking the original user guide, it says
> 
>       By default, equations are set in 10-point
>       type (the same size as this guide)
> 
> That was 40+ years ago.

Yup.  10-point remains "standard" in groff, but the foregoing will be
pretty blatantly wrong for the X100-12 and X75-12 output devices.

I will not dwell on the question of how many people _use_ those...

> For 30+ years (by which time I had a decent laser
> print), I always thought that it should have read
> 
>       By default, equations are set in the font size
>       as currently active where an equation occurs in
>       a document.
> 
> Am I missing something?  What is correct in this day and age?

That is not _quite_ right.  It is true often enough that people will get
themselves into trouble by assuming it is _always_ true.  Here's eqn(1)
on master.  I added this text in a pair of commits on 26 and 30 May.

Caveats
[...]
    Delimited equations are set at the type size current at the
    beginning of the input line, not necessarily that immediately
    preceding the opening delimiter.

I feel uncertain whether we should say more about the default type size
in the _man page_, when we don't offer similar reassurances in tbl(1) or
pic(1).  Of course those preprocessors don't change the type size except
as directed by the input.  Why would they?

It is also true that a macro package or user could (re)define the 'EQ'
macro to change the type size even for non-delimited equations.  But
that seems like something that would only be undertaken by experts.

Regards,
Branden

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