Re: [boost] [proto] weird transform behaviour

From: Maurizio Vitale (mav_at_[hidden])
Date: 2007-05-10 14:35:58

Thanks Eric,

Eric Niebler <eric_at_[hidden]> writes:

>
> Yes, the assumption is that you will only be applying a transform to 
> expressions that match the grammar. You can enforce this via:
>
>    // make sure it matches
>    BOOST_MPL_ASSERT((matches<Expr, width_transform>));
>    // apply the transform
>    width_transform::call(expr, state, visitor);
>
> It would be nice if it failed loudly, instead of silently doing the 
> wrong thing, though. I'll looking into changing this.

Would be very nice to have, if doable. Otherwise, should be spelled out
very clearly in the documentation, in case it is not now.

In my case there's one grammar passed to the domain, but then there're
many others embedded in transforms and their structure is typically
different. For instance, in the general grammar you typically have one
pattern capturing all binary expressions, but then for specific
transforms you may need to have more refined patterns and it is
probably rather easy to forget to cover some parts of the space
covered by the general grammar.

Regards,

        Maurizio