std::ranges::swap (3) - Linux Manuals

std::ranges::swap: std::ranges::swap


std::ranges::swap - std::ranges::swap


Defined in header <concepts>
inline namespace /* unspecified */ { (since C++20)
inline constexpr /* unspecified */ swap = /* unspecified */; (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:

* template<class T> void swap(T&, T&) = delete;
* template<class T, std::size_t N> void swap(T(&)[N], T(&)[N]) = delete;
* any declarations of swap found by argument-dependent_lookup.

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.

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.


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:
noexcept(std::is_nothrow_move_constructible_v<V> &&


 This section is incomplete
 Reason: no example

See also

Swappable specifies that a type can be swapped or that two types can be swapped with each other
SwappableWith (concept)

              swaps the values of two objects
swap (function template)