Re: [Boost-users] MPL Map of types to integral values

From: Cromwell Enage (sponage_at_[hidden])
Date: 2007-11-16 21:22:21

--- Robert Dailey wrote:
> So far, this is all I've been able to come up with:
> 
> #include <boost/mpl/map.hpp>
> #include <boost/mpl/at.hpp>
> 
> namespace detail
> {
>     template< unsigned int t_value >
>     struct integral
>     {
>         static const unsigned int value = t_value;
>     };
> 
>     typedef boost::mpl::map<   
> boost::mpl::pair<float, integral<GL_FLOAT>
> >,
>                                
> boost::mpl::pair<double, integral<GL_DOUBLE>
> >
>                             > glTypeMap;
> };
> 
> template< typename t_type >
> struct Vertex
> {
>     static const unsigned int type =
> boost::mpl::at<detail::glTypeMap,
> t_type>::type::value;
>     t_type x, y, z;
> };

Try this:

#include <boost/mpl/integral_c.hpp>
#include <boost/mpl/map.hpp>
#include <boost/mpl/at.hpp>

namespace detail {
    using namespace boost;
    using namespace mpl;

    typedef map<
        pair<
            float
          , integral_c<unsigned int,GL_FLOAT>
        >
      , pair<
            double
          , integral_c<unsigned int,GL_DOUBLE>
        >
    > glTypeMap;

    template <typename t_type>
    struct Vertex
    {
        static const unsigned int type =
            at<glTypeMap,t_type>::type::value;
        t_type x, y, z;
    };
}  // namespace detail

                              HTH,
                              Cromwell D. Enage

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