sharing grammar rules across grammars?

[Jeremy Elson]

Hi,

I have two languages that have several features in common.  Is there
an easy way to share rules across grammars?  (Both grammars use the
same lexer; the token values are the same.)

Right now, I'm just doing cut-and-paste of the rules, which of course
is not a very good solution.  Is there a way to do an "#include" from
within the rules section of a bison input, so that I can put the
common rules into a separate file that is included by both .y files?

By the way, I'm also using the evil cut-and-paste method to make sure
that both of my grammars have the same "%token" declarations, in the
same order, so that both grammars use the same token values and
therefore can share a lexer.  Is there a better way to keep the token
values in sync across grammars?  In reading the past year of mailing
list archives, I've seen similar questions, but never a definitive
answer.

Thanks!

-Jeremy