meta::weakly_equality_comparable_with¶
Defined in header <mgs/meta/concepts/weakly_equality_comparable_with.hpp>.
template <typename T, typename U>
concept weakly_equality_comparable_with =
requires(std::remove_reference_t<T> const& t,
std::remove_reference_t<U> const& u) {
{ t == u } -> meta::boolean;
{ t != u } -> meta::boolean;
{ u == t } -> meta::boolean;
{ u != t } -> meta::boolean;
};
Pre-C++20 implementation of the exposition-only weakly-equality-comparable-with concept.
Concept emulation¶
namespace mgs {
namespace meta {
template <typename T, typename U>
struct is_weakly_equality_comparable_with { /* ... */ };
template <typename T, typename U>
constexpr auto is_weakly_equality_comparable_with_v =
is_weakly_equality_comparable_with<T, U>::value;
template <typename T, typename U,
typename = std::enable_if_t<is_weakly_equality_comparable_v<T, U>>>
using weakly_equality_comparable_with = T;
} // namespace meta
} // namespace mgs
Example¶
#include <mgs/meta/concepts/weakly_equality_comparable_with.hpp>
struct A {};
struct B {};
bool operator==(A, A);
bool operator!=(A, A);
bool operator==(B, B);
bool operator!=(B, B);
bool operator==(A, B);
bool operator==(B, A);
bool operator!=(A, B);
bool operator!=(B, A);
static_assert(is_weakly_equality_comparable_with_v<int, float>, "");
static_assert(is_weakly_equality_comparable_with_v<A, B>, "");
static_assert(!is_equality_comparable_with_v<A, B>, "");