std::common_reference_with
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common_reference_with
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Exposition-only concepts
(C++20)
Defined in header
<concepts>
template< class T, class U >
(since C++20)
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>> &&
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
t1equalst2; and - std::common_reference_t <T, U>(u1) equals std::common_reference_t <T, U>(u2) if and only if
u1equalsu2.
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]
- 18.4.5 Concept
- C++20 standard (ISO/IEC 14882:2020):
- 18.4.5 Concept
common_reference_with[concept.commonref]
- 18.4.5 Concept