traits/promote3.hpp

The following code example is taken from the book
C++ Templates - The Complete Guide
by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002
© Copyright David Vandevoorde and Nicolai M. Josuttis 2002


#define MK_PROMOTION(T1,T2,Tr)             \
    template<> class Promotion<T1, T2> {   \
      public:                              \
        typedef Tr ResultT;                \
    };                                     \
                                           \
    template<> class Promotion<T2, T1> {   \
      public:                              \
        typedef Tr ResultT;                \
    };