support for string_view

[akonskarm]

Hi

Have you considered adding support for string_view for the _from_string methods?
It doesn't convert to char * so _names_match, _from_string and _from_string_loop would need to be overloaded.

BETTER_ENUM(Channel, char, Red = 1, Green, Blue)
int main() {
  std::experimental::string_view s("Blue");
  auto c = Channel::_from_string_nothrow(s);
  std::cout << *c << std::endl;
  return(0);
}

[aantron]

Hi :)

I've looked at it briefly, and it seems like a good thing to add. I haven't had time to properly do it, though.

[aantron]

One minor annoyance is it will probably need conditional compilation, based on compiler version and an override macro to force the overloads to be enabled for when the version detection does the wrong thing.

[akonskarm]

Yes, also because some compiler versions support only <experimental/string_view> and newer ones have <string_view>

The code below worked for me

BETTER_ENUMS_CONSTEXPR_ inline bool _names_match(const char *stringizedName,
                                                 std::experimental::string_view &referenceName,
                                                 std::size_t index = 0)
{
    return
        _ends_name(stringizedName[index]) ? index == referenceName.size() :
        index == referenceName.size() ? false :
        stringizedName[index] != referenceName[index] ? false :
        _names_match(stringizedName, referenceName, index + 1);
}

    BETTER_ENUMS_CONSTEXPR_ static _optional                                    \
    _from_string_nothrow(std::experimental::string_view s);                     \
\
    BETTER_ENUMS_CONSTEXPR_ static _optional_index                              \
    _from_string_loop(std::experimental::string_view &s, std::size_t index = 0);\

BETTER_ENUMS_CONSTEXPR_ inline Enum::_optional_index                            \
Enum::_from_string_loop(std::experimental::string_view &s, std::size_t index)   \
{                                                                               \
    return                                                                      \
        index == _size() ? _optional_index() :                                  \
        ::better_enums::_names_match(                                           \
            BETTER_ENUMS_NS(Enum)::_raw_names()[index], s) ?                    \
            _optional_index(index) :                                            \
            _from_string_loop(s, index + 1);                                    \
}                                                                               \
\
BETTER_ENUMS_CONSTEXPR_ inline Enum::_optional                                  \
Enum::_from_string_nothrow(std::experimental::string_view s)                    \
{                                                                               \
    return                                                                      \
        ::better_enums::_map_index<Enum>(                                       \
            BETTER_ENUMS_NS(Enum)::_value_array, _from_string_loop(s));         \
}

[aantron]

Thanks for that.

I won't have the time to integrate it in the immediate future (because of all that conditional compilation testing that would be needed).

If you'd like to give it a try, you're welcome to open a PR and test in the Better Enums CI setup. I think it might need to be updated to use some more recent compilers in its build rows.

I'm not sure what to do about std::experimental. Is it right that that namespace is not forwards-compatible (I never knew whether it is or isn't, actually), or something in there is guaranteed to stay? If not, we would probably want to avoid it entirely, and support only compilers that have std::string_view.

[sdebionne]

I am also interested in this feature. I think support for std::string_view is good enough. I might have a shot at this, is there anyone currently working on this feature request?

[aantron]

Thanks. Not to my knowledge.