multiple grammars/parser with common parts

[Thomas Lavergne]

Hi all,
I think I can now figure out how to write grammar files and use the 
semantic actions to create my objects with specified arguments. However, 
I have a question  more on the conception point of vie of complex 
packages using  bison/flex:
Here is the situation. Imagine I have classes representing geometrical 
objects (spheres, rectangles,...). I have an executable Exe1 which wants 
to perform the instantiation of objects while parsing an input file with 
bison's actions. That's fine with one bison parser interfaced with 
yyparse(). Now, let's imagine I want to write another executable Exe2 
which uses part of the same grammar (and underlying classes, hence the 
same grammar actions) along with other classes and grammar rules that 
are specific to him. I do not want to duplicate the common part of these 
two grammars because it is time consumming and will soon be a pain to 
maintain ; and I do not want Exe1 to learn for the part of grammar that 
is specific to Exe2 (and vice-versa).
The question is how can I have multiple parsers with common parts in 
their grammar (both symbolic and semantic)?

In my parser file (bison.y), I am allowed to use #include, #ifdef, 
etc... so I think I can manage this by compiling twice my bison.y but 
with different prefix (-p prefix) and some #ifdef EXE1 and #ifdef EXE2 
blocks. Anyway, I would like to know if there is any other solution 
(providing that this one works: not tested)?

Thanks for reading me and proposing your ideas.
Thomas