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; };
                }
        }
}