Difference between revisions of "cpp/concepts/common reference with"
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| − | {{cpp/title|common_reference_with}} | + | {{cpp/title|common_reference_with {{mark since c++20}}}} |
{{cpp/concepts/navbar}} | {{cpp/concepts/navbar}} | ||
{{ddcl|header=concepts|since=c++20|1= | {{ddcl|header=concepts|since=c++20|1= | ||
template< class T, class U > | template< class T, class U > | ||
concept common_reference_with = | 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>>; | |
}} | }} | ||
The concept {{tt|common_reference_with<T, U>}} specifies that two types {{tt|T}} and {{tt|U}} share a ''common reference type'' (as computed by {{lc|std::common_reference_t}}) to which both can be converted. | The concept {{tt|common_reference_with<T, U>}} specifies that two types {{tt|T}} and {{tt|U}} share a ''common reference type'' (as computed by {{lc|std::common_reference_t}}) to which both can be converted. | ||
| Line 17: | Line 17: | ||
In other words, the conversion to the common reference type must [[cpp/concepts#Equality preservation|preserve equality]]. | In other words, the conversion to the common reference type must [[cpp/concepts#Equality preservation|preserve equality]]. | ||
| − | {{ | + | ===References=== |
| + | {{ref std c++23}} | ||
| + | {{ref std|section=18.4.5|title=Concept {{tt|common_reference_with}}|id=concept.commonref}} | ||
| + | {{ref std end}} | ||
| + | {{ref std c++20}} | ||
| + | {{ref std|section=18.4.5|title=Concept {{tt|common_reference_with}}|id=concept.commonref}} | ||
| + | {{ref std end}} | ||
===See also=== | ===See also=== | ||
Latest revision as of 10:02, 7 September 2024
| Defined in header <concepts>
|
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| template< class T, class U > concept common_reference_with = |
(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) 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
[edit] See also
| determines the common reference type of a group of types (class template) | |
| (C++20) |
specifies that two types share a common type (concept) |
| (C++11) |
determines the common type of a group of types (class template) |
