std::common_reference_with

Defined in header <concepts>
template < class T, class U > concept common_reference_with = std::same_as < std::common_reference_t <T, U>, std::common_reference_t <U, T>> && std::convertible_to <T, std::common_reference_t <T, U>> && std::convertible_to <U, std::common_reference_t <T, U>> ;		(since C++20)

The concept common_reference_with<T, U> specifies that two types T and U share a common reference type (as computed by std::common_reference_t

Semantic requirements

T and U model std::common_reference_with<T, U> only if, given equality-preserving expressions t1, t2, u1 and u2 such that decltype((t1)) and decltype((t2)) are both T and decltype((u1)) and decltype((u2)) are both U

• std::common_reference_t <T, U> (t1) equals std::common_reference_t <T, U> (t2) if and only if t1 equals t2
• std::common_reference_t <T, U> (u1) equals std::common_reference_t <T, U> (u2) if and only if u1 equals u2

In other words, the conversion to the common reference type must preserve equality.

References

See also

common_referencebasic_common_reference (C++20)	determines the common reference type of a group of types (class template)
common_with (C++20)	specifies that two types share a common type (concept)
common_type (C++11)	determines the common type of a group of types (class template)