Re: [ublas] Numeric traits for ublas bounded_vector and matrix

Subject: Re: [ublas] Numeric traits for ublas bounded_vector and matrix
From: Rutger ter Borg (rutger_at_[hidden])
Date: 2010-02-23 11:38:05

Jesse Perla wrote:

> 
> Note here that the ::type is necessary here.  But now that I look at it,
> The problem may be that the result_of in this specific case doesn't use
> metafunction forwarding, whereas my naive implementation of static_size
> did... And hence it had the nested value automatically.
> 
> Also note that the following does NOT compile and looks like it should:
> 
> static const int N2 = boost::mpl::if_<
>     boost::numeric::bindings::has_static_size< double[10] >,
> boost::numeric::bindings::result_of::size< double[10] >,
>     boost::mpl::int_<0>
>>::type::value;
> 
> static const int J2 = boost::mpl::if_<
>     boost::numeric::bindings::has_static_size< std::vector<double> >,
>     boost::numeric::bindings::result_of::size< std::vector<double> >,
>     boost::mpl::int_<0>
>>::type::value;
> 

This compiles,

    static const int N = boost::mpl::if_<
        bindings::has_static_size< double[10] >,
        bindings::result_of::size< double[10] >::type,
        boost::mpl::int_<0>
    >::type::value;

    std::cout << N << std::endl;

    static const int J = boost::mpl::if_<
        bindings::has_static_size< std::vector<double> >,
        bindings::result_of::size< std::vector<double> >::type,
        boost::mpl::int_<0>
    >::type::value;

    std::cout << J << std::endl;

but indeed, perhaps the result_of::size needs extra mpl-stuff so that it is 
a better mpl-citizen. Perhaps it needs an extra typedef or something 
(apply?), that's an area of the mpl I've haven't used that much yet, so 
hints are welcome.

Cheers,

Rutger