enum_as_flags.hpp

enum_as_flags.hpp

#ifndef COPYRAT90_ENUM_AS_FLAGS_HPP
#define COPYRAT90_ENUM_AS_FLAGS_HPP

#include <type_traits>

#define ENUM_AS_FLAGS(Enum) \
    static_assert(std::is_enum<Enum>::value, "Template argument for Enum is not an enum."); \
\
    constexpr bool operator!(Enum a) { \
        using Int = typename std::underlying_type<Enum>::type; \
        return !static_cast<Int>(a); \
    } \
\
    constexpr Enum operator~(Enum a) { \
        using Int = typename std::underlying_type<Enum>::type; \
        return static_cast<Enum>(~static_cast<Int>(a)); \
    } \
\
    constexpr Enum operator|(Enum a, Enum b) { \
        using Int = typename std::underlying_type<Enum>::type; \
        return static_cast<Enum>(static_cast<Int>(a) | static_cast<Int>(b)); \
    } \
\
    constexpr Enum& operator|=(Enum& a, Enum b) { \
        return a = a | b; \
    } \
\
    constexpr Enum operator&(Enum a, Enum b) { \
        using Int = typename std::underlying_type<Enum>::type; \
        return static_cast<Enum>(static_cast<Int>(a) & static_cast<Int>(b)); \
    } \
\
    constexpr Enum& operator&=(Enum& a, Enum b) { \
        return a = a & b; \
    } \
\
    constexpr Enum operator^(Enum a, Enum b) { \
        using Int = typename std::underlying_type<Enum>::type; \
        return static_cast<Enum>(static_cast<Int>(a) ^ static_cast<Int>(b)); \
    } \
\
    constexpr Enum& operator^=(Enum& a, Enum b) { \
        return a = a ^ b; \
    }

#endif

usage.cpp

#include "enum_as_flags.hpp"

enum class MyFlags {
    NONE = 0,
    A = 1 << 0,
    B = 1 << 1,
    C = 1 << 2,
    D = 1 << 3,
    ALL = A | B | C | D
};

ENUM_AS_FLAGS(MyFlags);

int main() {
    constexpr MyFlags f = MyFlags::A | MyFlags::B;

    // Check if `f` has `MyFlags::A` in it
    static_assert(!!(f & MyFlags::A));
}