std::common_reference_with - cppreference.com (original) (raw)

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) to which both can be converted.

[edit] 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; and
• 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.

[edit] References

• C++23 standard (ISO/IEC 14882:2024):

• 18.4.5 Concept common_reference_with [concept.commonref]

• C++20 standard (ISO/IEC 14882:2020):

• 18.4.5 Concept common_reference_with [concept.commonref]

[edit] See also