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Re: [Groff] .ss problem

From: Tadziu Hoffmann
Subject: Re: [Groff] .ss problem
Date: Fri, 18 May 2001 10:23:41 +0200

> > > > Before fixing, a general question.  In Unix troff, .ss is ignored
> > > > if in nroff mode.  Shall GNU troff behave identically if
> > > > compatibility mode is on?  Does it really make sense to `cripple'
> > > > GNU troff for compatibility reasons?

The interesting thing is that the Troff User's Manual states
that (Unix) nroff has an option to ``produce equally-spaced
words in adjusted lines, using full terminal resolution.''
If this implies that there are typewriter-like devices with
better-than-character-cell horizontal positioning, it makes one
wonder why `.ss' should be ignored completely in nroff, instead
of the more natural notion that `.ss' should accept all
arguments compatible with the horizontal resolution of the

Therefore, I would agree that source-level compatibility is
much more important than exactly mimicking seldom-used features
--- meaning, ``behaves as intended'' (whatever we choose to mean
by that) rather than ``behaving exactly as''.
(Did anybody ever rely on `.ss' being ignored in nroff, anyway?)

Remember, this issue is actually the largest ``philosophical''
difference between TeX and troff:  whereas TeX intends to give
the same formatting on all devices (which is then ``realized''
as best as possible by the DVI driver), troff attempts to give
the best formatting possible for the device.  On this premise,
it is permissible for ``my'' [g]troff to give different
formatting than ``your'' [g]troff for the same output device,
as long as macros and requests behave similarly in the sense
that they behave similarly when formatting for different output

With this in mind, I agree with everybody else in that it does
make sense to support `.ss' also in nroff mode.

> In that case I think it is more fair to say that we have a GNU troff
> but no GNU nroff.  Our troff just happens to be able to output to
> tty-like devices [...]

Well, actually that's really not too different from Unix troff:
According to The Manual,

  nroff necessarily cannot support all features of troff. Within
  that limitation, it is the same as troff, and in fact there is
  only a single program invoked by two different names.


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