C++17 interop: std::optional

[jaskij]

In my embedded project, I utilize std::optional heavily. Unfortunately, better_enum::optional doesn't have a built in conversion.

I can see two options:

• in C++17 and newer projects, replace better_enum::optional with std::optional
• provide a conversion function to std::optional

Here's a member conversion function I threw together quickly:

    #if defined(__cpp_lib_optional) && (__cpp_lib_optional >= 201606L)
    BETTER_ENUMS_CONSTEXPR_ operator std::optional<T>() const {
        if(*this) {return {_value};}
        else {return std::nullopt;}
    }
    #endif

[aantron]

Thank you! Would you be willing to propose this as a PR?

[jaskij]

Sure thing. I wasn't sure if that quickly put together operator was good enough, but if it is, I'll go ahead and submit a PR.