Enum comparison without a + operator

[yan-zaretskiy]

Is it possible to avoid the plus operator for the comparisons between an Enum and Enum::_enumerated?

[yan-zaretskiy]

I tried to define

bool operator==(MyEnum left, MyEnum::_enumerated right) {
  return left._to_integral() == right;
}

This seems to work. Am I thinking along the correct lines?

[aantron]

Every way I know (knew) of avoiding the + operator had the side effect of introducing ambiguous overload resolution elsewhere. See comments here:

#23 (comment)
#13 (comment)

I grant that I may have missed something. Have you run the tests with your modification?

[yan-zaretskiy]

Hmm, trying to build tests complains about the absence of the cxxtest/tests.cc file...
Nevermind, install cxxtest...

[yan-zaretskiy]

All errors I see are in the 101-special-values.cc file where you define the invalid_t and default_t types, other tests can be built and they pass.

[yan-zaretskiy]

So, just for the reference, cause I don't really know what I'm doing, I added the following lines:

BETTER_ENUMS_UNUSED BETTER_ENUMS_CONSTEXPR_                                    \
inline bool operator ==(const Enum &a, const Enum::_enumerated &b)             \
    { return a._to_integral() == b; }                                          \
                                                                               \
BETTER_ENUMS_UNUSED BETTER_ENUMS_CONSTEXPR_                                    \
inline bool operator ==(const Enum::_enumerated &a, const Enum &b)             \
    { return a == b._to_integral(); }                                          \
                                                                               \
BETTER_ENUMS_UNUSED BETTER_ENUMS_CONSTEXPR_                                    \
inline bool operator !=(const Enum &a, const Enum::_enumerated &b)             \
    { return a._to_integral() != b; }                                          \
                                                                               \
BETTER_ENUMS_UNUSED BETTER_ENUMS_CONSTEXPR_                                    \
inline bool operator !=(const Enum::_enumerated &a, const Enum &b)             \
    { return a != b._to_integral(); }                                          \