Re: [Groff] Typesetting dashes

[Tadziu Hoffmann]

> I should like to typeset em dashes surrounded by thin,
> say 1/4th en, spaces.  To prevent a dash from starting a
> new line, the first space must be unbreakable.  The second
> one must be discardable.  Both spaces must be unstretchable.
> How to do it?

  .ds EM \R'SS \\n[.s]/2'\s'\\n[SS]'\ \s0\[em]\s'\\n[SS]'\: \s0
  This is\*[EM]in all respects\*[EM]quite tricky.

In the original troff (according to the Troff User's Manual)
a space was nominally 1/3 em and a thinspace was 1/6 em,
thus half a normal space.  In groff's TR font, a space
is nominally 1/4 em, but a thinspace is still only 1/6 em.
Isn't that strange?

Anyhow, 1/4 en thus corresponds to half a normal space in
groff's TR font.  Don't ask me why the "\:" converts the
following space into a nonstretchable (but discardable) space.



I'm not really happy with this solution.  I'd prefer space
that stretches proportionally to the font size, but this
doesn't seem to work in groff:  groff appears to compute the
total stretch divided by the number of spaces, and then *adds*
this to *all* spaces, independent of their nominal size.
I think this is wrong and should be changed.
What do you all think?