[boost] Re: Re: Re: Spirit and typeof [was typeof]

From: Arkadiy Vertleyb (vertleyb_at_[hidden])
Date: 2004-05-05 12:53:09

"Reece Dunn" <msclrhd_at_[hidden]> wrote

> This was what I was thinking. But is there a way of handling the grammar
> template as a special case, e.g.:
>
>    template< typename T >
>    class deduce_type
>    {
>       typedef ... type;
>    };
>
>    template< typename DerivedT >
>    class deduce_type< boost::spirit::grammar< DerivedT > >
>    {
>       typedef DerivedT::type type;
>    };
>
> I am not saying that this is what it will look like as I am not up to
speed
> with your typeof mechanism, but if something similar could be implemented,
> it would make custom grammars more powerful (may even reduce the number of
> types that need explicit registration).

Hmmm, I am afraid this might not be possible...  Once your DerivedT is
present anywhere in the template tree, the typeof mechanism needs to know
about it in order to be able to encode/decode it.  This applies to any type
or template.  The library-defined types/templates can (and should) be
registered by the library, but once a user defines a new type, it has to be
registered too, by the user.

Regards,
Arkadiy