Re: [Groff] parsing a corner specification

[Dwight Aplevich]

Hello

If it helps, you are correct.  The dpic compass-corner
definitions are given in the documentation.  The "upper"
and "lower" keywords are not defined. I can only suggest
that instead of writing

B: A upper left

write

B: A.nw

which will work both for gpic and dpic.

DA

At 04:41 PM 19/08/2007, Joel E. Denny wrote:
> On Sun, 19 Aug 2007, Werner LEMBERG wrote:
>
> > > > I've searched the web and Open Group for some roff or pic
> > > > standards document.  So far, I haven't found one.  Does one exist?
> > >
> > >     <http://plan9.bell-labs.com/cm/cs/cstr/116.ps.gz>
> >
> > Search for `pic.ps' (made from `pic.ms') in case you have groff
> > installed.  This documentation contains a complete annotated grammar.
>
> Thanks.  It looks like both grammars exclude some constructs accepted by
> GNU pic.  For example:
>
>   B: A
>
> and:
>
>   B: A upper left
>
> > Note that GNU pic tries to be compatible with the AT&T pic; this
> > probably explains some of the strange grammar constructs
>
> How can I obtain a copy of AT&T pic?  This page makes it seem as if I
> won't have much luck:
>
>   http://troff.org/source.html
>
> It links to Plan 9, which has pic source here:
>
>   http://plan9.bell-labs.com/sources/plan9/sys/src/cmd/pic/
>
> Its lexer returns left as a CORNER token only when preceded by "." or
> followed by "of", so it can't be the inspiration for the GNU pic behavior
> I'm observing.
>
> The Heirloom project has similar source and its lexer does the same thing:
>
>   http://heirloom.cvs.sourceforge.net/heirloom/heirloom-doctools/pic/
>
> > On the other hand, you might also test with `dpic', which also
> > documents various differences of GNU pic, dpic, and the original AT&T
> > pic.
>
> Thanks.  In their list of differences, the most relevant item I found was
> this:
>
>   compass corners:
>     dpic consistently requires a dot before compass corners, so the gpic
>   line
>       "x" at center of last box
>     should be written for dpic as
>       "x" at .center of last box
>
> So, dpic accepts neither of my original examples:
>
>   B: A upper left
>   B: A left
>
> As far as I can tell, dpic does not recognize the "upper" keyword.  The
> second example must be changed to the following to be accepted by dpic:
>
>   B: A.left
>
> This is also accepted by GNU pic without switching to canonical LR(1).
>
> I'm getting the strong impression that I'm looking at a very obscure usage
> of GNU pic.  Would you agree?

Dwight Aplevich