Difference between revisions of "cpp/algorithm/swap"

Revision as of 11:27, 13 March 2016

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 is overload resolution unless std::is_move_constructible_v<T> && std::is_move_assignable_v<T>(since C++17)

2) Swaps the arrays a and b. In effect calls std::swap_ranges(a, a+N, b).

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 Template:concept for details.

The following overloads are already provided by the standard library:

std::swap(std::pair) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::tuple) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::shared_ptr) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::weak_ptr) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::unique_ptr) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::function) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::basic_string)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::array) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::deque)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::forward_list) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::list)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::vector)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::map)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::multimap)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::set)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::multiset)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::unordered_map) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::unordered_multimap) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::unordered_set) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::unordered_multiset) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::queue) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::priority_queue) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::stack) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::valarray) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::basic_stringbuf) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::basic_istringstream) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::basic_ostringstream) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::basic_stringstream) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::basic_filebuf) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::basic_ifstream) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::basic_ofstream) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::basic_fstream) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::basic_regex) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::match_results) (C++11)	specializes the `std::swap` algorithm (function template) [edit]
swap(std::) ({{{1}}})	specializes the std::swap algorithm (function) [edit]
std::swap(std::unique_lock) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::promise) (C++11)	specializes the std::swap algorithm (function template) [edit]
std::swap(std::packaged_task) (C++11)	specializes the std::swap algorithm (function template) [edit]

Example

Run this code

#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

@@ Line 15: / Line 15: @@
 Exchanges the given values.
-@1@ Swaps the values {{tt|a}} and {{tt|b}}.
+@1@ Swaps the values {{tt|a}} and {{tt|b}}. {{rev inl|since=c++17|This overload does not participate is overload resolution unless {{c|std::is_move_constructible_v<T> && std::is_move_assignable_v<T>}}}}
 @2@ Swaps the arrays {{tt|a}} and {{tt|b}}. In effect calls {{c|std::swap_ranges(a, a+N, b)}}.
@@ Line 39: / Line 39: @@
 }}
 }}{{rev end}}
-@2@ {{noexcept|noexcept(swap(*a, *b))}}
+@2@ {{rev begin}}
+{{rev|until=c++17|{{noexcept|noexcept(swap(*a, *b))}}}}
+{{rev|since=c++17|{{noexcept|std::is_nothrow_swappable_v<T>}}}}{{rev end}}
 ===Complexity===

Compiler support
Freestanding and hosted
Language
Standard library
Standard library headers
Named requirements
Feature test macros (C++20)
Language support library
Concepts library (C++20)
Metaprogramming library (C++11)
Diagnostics library
General utilities library
Strings library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Numerics library
Localizations library
Input/output library
Filesystem library (C++17)
Regular expressions library (C++11)
Concurrency support library (C++11)
Execution support library (C++26)
Technical specifications
Symbols index
External libraries

`noexcept` specification: noexcept(noexcept(swap(a, b)))	(until C++17)
`noexcept` specification: noexcept(std::is_nothrow_swappable_v<T>)	(since C++17)

iter_swap	swaps the elements pointed to by two iterators (function template) [edit]
swap_ranges	swaps two ranges of elements (function template) [edit]

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Difference between revisions of "cpp/algorithm/swap"

Revision as of 11:27, 13 March 2016

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a, b	-	the values to be swapped
Type requirements Template:par req concept Template:par req concept

(none)	(until C++11)
`noexcept` specification: noexcept( std::is_nothrow_move_constructible<T>::value && std::is_nothrow_move_assignable<T>::value )	(since C++11)