std::swappable, std::swappable_with

 

C++

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Technical specifications

Symbols index

External libraries

 

Concepts library

Core language concepts same_as derived_from convertible_to common_reference_with      common_with integral signed_integral unsigned_integral floating_point swappableswappable_with destructible constructible_from default_initializable move_constructible copy_constructible assignable_from

Comparison concepts equality_comparableequality_comparable_with totally_orderedtotally_ordered_with Object concepts movable copyable semiregular regular Callable concepts invocableregular_invocable predicate relation equivalence_relation strict_weak_order

Exposition-only concepts boolean-testable

 

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).