Re: [Groff] parsing a corner specification

[Joel E. Denny]

On Sat, 18 Aug 2007, Larry Jones wrote:

> Joel E. Denny writes:
> > 
> > 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>

Thanks for that reference.  As far as I can tell, the grammar in Appendix 
A does not accept this sentence:

  B: A upper left

I believe it doesn't even accept this one:

  B: A

I'm guessing that I'm dealing with extensions to that specification.  If 
so, are they specific to Groff?  How do the Groff developers intend for 
them to work?