Re: Conditional generation of Grammar rules

[Hans Aberg]

One way of handling this is to merge the two grammars, and making  
them selectable by a special token, which is then used at runtime.  
The .y grammar is entirely static, and is even thrown away by the LALR 
(1) algorithm that Bison uses, so the generated parser does not know  
anything about it, and in particular, cannot be accessed at all at  
parser runtime.

On 2 May 2006, at 18:37, Jeganatan, Srividhya wrote:

> All,
> 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.
>
> Thanks for your help.
>
> Srividhya.
>
>
>
>
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