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Difference between revisions of "cpp/algorithm/swap"

From cppreference.com
< cpp‎ | algorithm
(use templates)
m (Use since= and until= params of {{dcl}} template.)
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void swap( T& a, T& b );
 
void swap( T& a, T& b );
 
}}
 
}}
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{{dcl | num=2 | notes={{mark since c++11}} |
+
{{dcl | num=2 | since=c++11 |
 
template< class T2, size_t N >
 
template< class T2, size_t N >
 
void swap( T2 (&a)[N], T2 (&b)[N]);
 
void swap( T2 (&a)[N], T2 (&b)[N]);

Revision as of 15:31, 1 July 2013

 
C++
 
Algorithm library
Constrained algorithms and algorithms on ranges (C++20)
Constrained algorithms, e.g. ranges::copy, ranges::sort, ...
Execution policies (C++17)
Non-modifying sequence operations
Batch operations
(C++17)
Search operations
(C++11)                (C++11)(C++11)

Modifying sequence operations
Copy operations
(C++11)
(C++11)
(C++11)
Swap operations
swap
Transformation operations
Generation operations
Removing operations
Order-changing operations
(until C++17)(C++11)
(C++20)(C++20)
Sampling operations
(C++17)

Sorting and related operations
Partitioning operations
Sorting operations
Binary search operations
(on partitioned ranges)
Set operations (on sorted ranges)
Merge operations (on sorted ranges)
Heap operations
Minimum/maximum operations
(C++11)
(C++17)
Lexicographical comparison operations
(C++20)
Permutation operations
C library
Numeric operations
Operations on uninitialized memory
 
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.

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

Contents

Parameters

a, b - the values to be swapped
Type requirements

Template:par req concept Template:par req concept

Return value

(none)

Exceptions

1)
noexcept specification:  
noexcept(noexcept(

    std::is_nothrow_move_constructible<T>::value &&
    std::is_nothrow_move_assignable<T>::value

))
2)
noexcept specification:  
noexcept(noexcept(swap(*a, *b)))

Complexity

1) Constant

2) Linear in N

Specializations

Both custom specializations and overloads of the std::swap algorithm are allowed, but the overloads are generally preferred since specializations of a function template aren't allowed for template classes. Library functions always use the user-provided overloads when swapping, if they are found by argument-dependent lookup (as per Template:concept concept).

The following overloads are already provided by the standard library:

(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
specializes the std::swap algorithm
(function template) [edit]
specializes the std::swap algorithm
(function template) [edit]
specializes the std::swap algorithm
(function template) [edit]
specializes the std::swap algorithm
(function template) [edit]
specializes the std::swap algorithm
(function template) [edit]
specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
({{{1}}})
 specializes the std::swap algorithm
(function) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(C++11)
 specializes the std::swap algorithm
(function template) [edit]
(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

See also

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