[Groff] Question on -ms macro writing

[Greg Pavelcak]

I've been trying to get some ideas on macro writing by looking at
the existing tmac files, and I'm a little confused about the approach
in ms.  Why all of the aliases? NH is an alias for @NH; @NH uses
SH, which is an alias for @SH. It occurred to me that perhaps this
is a clever way to allow users to alter existing macro behavior.
For example, I could define SH in a file like this:

        .de SH
        address@hidden
        .fam H
        .ps 14
        ..

and use NH in the ordinary way, retaining its ms-prescribed
functionality but get Helvetica in my section headings.  I'm having
trouble getting this to work though. Have I missed the point, or
am I just doing something wrong?

Thanks.

Greg