std::experimental::ranges::Readable_C++中文网
template < class In >
concept bool Readable =
requires {
typename ranges::value_type_t<In>;
typename ranges::reference_t<In>;
typename ranges::rvalue_reference_t<In>;
} &&
ranges::CommonReference<
ranges::reference_t<In>&&, ranges::value_type_t<In>&
> &&
ranges::CommonReference<
ranges::reference_t<In>&&, ranges::rvalue_reference_t<In>&&
> &&
ranges::CommonReference<
ranges::rvalue_reference_t<In>&&, const ranges::value_type_t<In>&