Re: Conditional generation of Grammar rules

[David Fang]

> Is there a way to conditionally generate grammar rules?
> For example, I need to do something like
>
> nonterminal X:
> #ifdef FEATURE
>  { rule 1 }
> #else
>  { rule 1; rule 2 }
> #endif
>
> I know that ifdefs dont work with the grammar but is there anything
> else that can be done? Or is it possible to make bison to read define
> variables from a make file?
>
> I want to avoid writing different parsers / recursive parsers to do this.

Hi,
        You could generate your .y file explicitly using cpp, going from
.y.in -> .y, and using a separaete header to define your feature sets.
(I do something similar with autoconf-configure, for example.)  Or you
could generate it with a more sophisticated preprocessor like m4.

Fang