std::swappable, std::swappable_with
Defined in header <concepts> | ||
|---|---|---|
template< class T >
concept swappable =
requires(T& a, T& b) {
ranges::swap(a, b);
};
| (1) | (since C++20) |
template< class T, class U >
concept swappable_with =
std::common_reference_with<T, U> &&
requires(T&& t, U&& u) {
ranges::swap(std::forward<T>(t), std::forward<T>(t));
ranges::swap(std::forward<U>(u), std::forward<U>(u));
ranges::swap(std::forward<T>(t), std::forward<U>(u));
ranges::swap(std::forward<U>(u), std::forward<T>(t));
};
| (2) | (since C++20) |
The concept swappable<T> specifies that lvalues of type T are swappable.
The concept swappable_with<T, U> specifies that expressions of the type and value category encoded by T and U are swappable with each other. swappable_with<T, U> is satisfied only if a call to ranges::swap(t, u) exchanges the value of t and u, that is, given distinct objects t2 equal to t and u2 equal to u, after evaluating either ranges::swap(t, u) or ranges::swap(u, t), t2 is equal to u and u2 is equal to t.
Equality preservation
Expressions declared in requires expressions of the standard library concepts are required to be equality-preserving (except where stated otherwise).
References
- C++23 standard (ISO/IEC 14882:2024):
- 18.4.9 Concept
swappable[concept.swappable] - C++20 standard (ISO/IEC 14882:2020):
- 18.4.9 Concept
swappable[concept.swappable]
See also
|
(C++17)(C++17)(C++17)(C++17) | checks if objects of a type can be swapped with objects of same or different type (class template) |
|
(C++26)(C++26)(C++26)(C++26) | checks if objects of one reflected type can be swapped with objects of same or different other reflected type (function) |
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