> > 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.
Note that GNU pic tries to be compatible with the AT&T pic; this
probably explains some of the strange grammar constructs (due to time
constraints I haven't checked your specific problem).
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.
Werner