promote.h

#pragma once 
 
#include <cgv/type/func/drop_const.h>
#include <cgv/type/func/make_const.h>
#include <cgv/type/ctrl/if_.h>
 
namespace cgv {
    namespace type {
        namespace func {
            namespace Promote {
                template <typename T> struct promotion_rank { enum { rank = 1000 }; };
                template <> struct promotion_rank<bool>           { enum { rank =   0 }; };
                template <> struct promotion_rank<char>           { enum { rank =  10 }; };
                template <> struct promotion_rank<unsigned char>  { enum { rank =  20 }; };
                template <> struct promotion_rank<short>          { enum { rank =  30 }; };
                template <> struct promotion_rank<unsigned short> { enum { rank =  40 }; };
                template <> struct promotion_rank<int>            { enum { rank =  50 }; };
                template <> struct promotion_rank<unsigned int>   { enum { rank =  60 }; };
                template <> struct promotion_rank<long>           { enum { rank =  70 }; };
                template <> struct promotion_rank<unsigned long>  { enum { rank =  80 }; };
                template <> struct promotion_rank<float>          { enum { rank =  90 }; };
                template <> struct promotion_rank<double>         { enum { rank = 100 }; };
            }
            template <typename T1, typename T2> 
            struct promote
            {
                static const bool favour_first = 
                    (unsigned int) Promote::promotion_rank<T1>::rank >(unsigned int) Promote::promotion_rank<T2>::rank;
                typedef typename ctrl::if_<favour_first, T1, T2>::type type;
            };
            template <> struct promote<int,float>           { typedef double type; };
            template <> struct promote<float,int>           { typedef double type; };
            template <> struct promote<unsigned int,float>  { typedef double type; };
            template <> struct promote<float,unsigned int>  { typedef double type; };
            template <> struct promote<long,float>          { typedef double type; };
            template <> struct promote<float,long>          { typedef double type; };
            template <> struct promote<unsigned long,float> { typedef double type; };
            template <> struct promote<float,unsigned long> { typedef double type; };
        }
    }
}