< cpp‎ | utility
Defined in header <concepts>
inline namespace /* unspecified */ {

    inline constexpr /* unspecified */ swap = /* unspecified */;

(since C++20)
(customization point object)
Call signature
template< class T, class U >

    requires /* see below */

constexpr void swap(T&& t, U&& u) noexcept(/* see below */);

Exchanges the values referenced by t and u.

A call to ranges::swap is equivalent to:

1) (void)swap(std::forward<T>(t), std::forward<U>(u)), if that expression is valid, where the overload resolution is performed with the following candidates:
If the function selected by overload resolution does not exchange the values referenced by t and u, the program is ill-formed; no diagnostic required.
2) Otherwise, (void)ranges::swap_ranges(t, u), if T and U are lvalue references to array types of equal extent (but possibly different element types) and ranges::swap(*t, *u) is a valid expression;
3) Otherwise, if T and U are both V& for some type V that meets the syntactic requirements of MoveConstructible<V> and Assignable<V&, V>, exchanges the referenced values as if by V v{std::move(t)}; t = std::move(u); u = std::move(v);. If the semantic requirements of either concept are not satisfied, the program is ill-formed; no diagnostic required.
4) In all other cases, a call to ranges::swap is ill-formed.

ranges::swap can be used in a constant expression if every function it calls (as specified above) can be so used.


[edit] Customization point objects

The name ranges::swap denotes a customization point object, which is a function object of a literal Semiregular class type (denoted, for exposition purposes, as SwapT). All instances of SwapT are equal. Thus, ranges::swap can be copied freely and its copies can be used interchangeably.

Given a set of types Args..., if std::declval<Args>()... meet the requirements for arguments to ranges::swap above, SwapT will satisfy std::Invocable<const SwapT&, Args...>. Otherwise, no function call operator of SwapT participates in overload resolution.

[edit] Exceptions

noexcept specification:  
noexcept(noexcept((void)swap(std::forward<T>(t), std::forward<T>(u))))
, where swap is found as described above.
noexcept specification:  
noexcept(noexcept(ranges::swap(*t, *u)))
noexcept specification:  

[edit] Example

[edit] See also

specifies that a type can be swapped or that two types can be swapped with each other
(concept) [edit]
swaps the values of two objects
(function template) [edit]