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std::swap

Defined in header <algorithm>
Defined in header <utility>
(until C++11)
(since C++11)
template< class T >
void swap( T& a, T& b );
(1)
template< class T2, size_t N >
void swap( T2 (&a)[N], T2 (&b)[N]);
(2) (since C++11)

Exchanges the given values.

1) Swaps the values a and b. This overload does not participate in overload resolution unless std::is_move_constructible_v<T> && std::is_move_assignable_v<T> is true. (since C++17)
2) Swaps the arrays a and b. In effect calls std::swap_ranges(a, a+N, b). This overload does not participate in overload resolution unless std::is_swappable_v<T> is true. (since C++17)

Parameters

a, b - the values to be swapped
Type requirements
- T must meet the requirements of MoveAssignable and MoveConstructible.
- T2 must meet the requirements of Swappable.

Return value

(none).

Exceptions

1)
(none) (until C++11)
noexcept specification:
(since C++11)
2)
noexcept specification:
noexcept(noexcept(swap(*a, *b)))
(until C++17)
noexcept specification:
noexcept(std::is_nothrow_swappable_v<T>)
(since C++17)

Complexity

1) Constant
2) Linear in N

Specializations

std::swap may be specialized in namespace std for user-defined types, but such specializations are not found by ADL (the namespace std is not the associated namespace for the user-defined type). The expected way to make a user-defined type swappable is to provide a non-member function swap in the same namespace as the type: see Swappable for details.

The following overloads are already provided by the standard library:

specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap() algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap() algorithm
(function template)
specializes the std::swap algorithm
(function template)
specialization of std::swap for unique_lock
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function template)
specializes the std::swap algorithm
(function)
specializes the std::swap algorithm
(function)
specializes the std::swap algorithm
(function)
swaps two paths
(function)

Example

#include <algorithm>
#include <iostream>
 
int main()
{
   int a = 5, b = 3;
 
   // before
   std::cout << a << ' ' << b << '\n';
 
   std::swap(a,b);
 
   // after
   std::cout << a << ' ' << b << '\n';
}

Output:

5 3
3 5

See also

swaps the elements pointed to by two iterators
(function template)
swaps two ranges of elements
(function template)

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