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Re: [Groff] bug in GNU troff?


From: Werner LEMBERG
Subject: Re: [Groff] bug in GNU troff?
Date: Mon, 22 Jan 2001 10:10:45 +0100 (CET)

> First stab, how about this.
> 
>     .ta 1iR +1i
>     Margin  Right   Left
>     .br
>     x       x       Positive
>     .br
>     x       x\c
>             Negative
> 
> It gives
> 
>     Margin     Right          Left
>     x              x          Positive
>     x              x  Negative
> 
> Is that what you mean?

Yes!  Thanks a lot.  Seeing an actual example gives a meaning to the
tab behaviour.  I haven't thought about left and right justified tabs.

> ... there seems to me to be a difference between *extending* groff
> with long names, although incompatible with troff's parsing in a few
> cases, and re-defining the meaning on a tab in the input.  I agree,
> it is a question of judgement, but changing the meaning of tab on
> input just seems a step too far.

OK, you've convinced me that the default behaviour of a tab should
stay as it is.  Nevertheless, I will eventually add a request, say,
`.linetabs [0|1]', which will honour partial lines.

> Compatibility mode is too coarse a granularity.  If on then long
> names are sorely lacking.  A set of compatibility flags to control
> each group of extensions might help.

What `group of extensions' do you mean?  Is there anything else in
groff's default mode which you don't like?

> Does TeX suffer from being a museum?  Am I right in thinking Knuth
> has fixed its definition and therefore freedom to tweak and twiddle
> is limited?  Troff's definition is pretty fixed too, and wandering
> away from it might be unwise.

All programs which pass the `trip test' are allowed to be called TeX.
Knuth himself always thought that people will quickly start to modify
TeX (the program), suiting the actual needs.  It is an irony of
history that it took almost 20 years that this has started to happen:
pdfTeX, eTeX, Omega, NTS, ant, ...  Most of these programs have a
`compatibility mode' which exactly mimic TeX's behaviour.

I wish such a trip test existed for troff also -- running it tests
more than 99% of TeX's code.


    Werner

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