meta::common_reference_with¶

Defined in header <mgs/meta/concepts/common_reference_with.hpp>.

template <typename T, typename U>
concept common_reference_with =
   meta::same_as<meta::common_reference_t<T, U>, meta::common_reference_t<U, T>> &&
   meta::convertible_to<T, meta::common_reference_t<T, U>> &&
   meta::convertible_to<U, meta::common_reference_t<T, U>>;

Pre-C++20 implementation of the std::common_reference_with concept.

Concept emulation¶

namespace mgs {
namespace meta {

template <typename T, typename U>
struct has_common_reference_with { /* ... */ };

template <typename T, typename U>
constexpr auto has_common_reference_with_v = has_common_reference_with<T, U>::value;

template <typename T, typename U,
          typename = std::enable_if_t<has_common_reference_with_v<T, U>>>
using common_reference_with = T;

} // namespace meta
} // namespace mgs

Example¶

#include <mgs/meta/concepts/common_reference_with.hpp>

using namespace mgs::meta;

static_assert(has_common_reference_with_v<int&, short&>, "");
static_assert(has_common_reference_with_v<int const&, int volatile&>, "");
static_assert(!has_common_reference_with_v<int, char (&)[]>, "");

See also¶