I think that "numeric_cast" should be able to cast to and from enum types, so that it can be used as follows:

#include <cstdint>

#include <iostream>

using std::cout;

using std::endl;

enum class Frog { Blue, Yellow, Pink = 0xFFFFu };

enum class Toad : std::uint8_t { Purple, Orange = 0x7f };

int main(void)

{

    try { numeric_cast<Toad>( Frog::Pink ); } catch(std::exception const &e) { cout << e.what() << endl; }

    std::uint32_t my_32_bit_var = 0xffffffffU;

    try { numeric_cast<std::uint16_t>(my_32_bit_var); } catch(std::exception const &e) { cout << e.what() << endl; }

    try { numeric_cast<std::uint8_t>( Frog::Pink ); } catch(std::exception const &e) { cout << e.what() << endl; }

    try { numeric_cast<Toad>(0x1FFu); } catch(std::exception const &e) { cout << e.what() << endl; }

}

In order to achieve this behaviour, I've created my own "numeric_cast" in the global namespace as follows:

#include <type_traits> // is_enum, underlying_type

#include <boost/numeric/conversion/cast.hpp> // numeric_cast

template<bool T_is_an_enum, typename T>

struct numeric_cast_helper {

    typedef T type;

};

template<typename T>

struct numeric_cast_helper<true, T> {

    typedef typename std::underlying_type<T>::type type;

};

template<typename A, typename B>

A numeric_cast(B const b)

{

    return

    static_cast<A>(

        boost::numeric_cast<typename numeric_cast_helper<std::is_enum<A>::value, A>::type>

        (

            static_cast<typename numeric_cast_helper<std::is_enum<B>::value, B>::type>(b)

        )

    );

}

Should the Boost Numeric library be changed so that numeric_cast can work with enum's?