std::swap
STD：互换
| Defined in header | | (until C++11)(since C++11) |
|---|---|---|
| template< class T > void swap( T& a, T& b | (1) | |
| template< class T2, std::size_t N > void swap( T2 (&a)N, T2 (&b)N | (2) | (since C++11) |
交换给定的值。
1%29交换值a和b此重载不参与过载解决，除非std::is_move_constructible_v<T>&&std::is_move_assignable_v<T>是true.%28自C++17%29
2%29交换数组a和b.实际上是打电话std::swap_ranges(a, a+N, b)此重载不参与过载解决，除非std::is_swappable_v<T2>是true.%28自C++17%29
参数
| a, b | - | the values to be swapped |
|---|
类型要求
-T必须符合可转让和可移动的要求。
-T2必须符合可互换的要求。
返回值
%280%29
例外
1%29
| (none) | (until C++11) |
|---|---|
| noexcept specification: noexcept( std::is_nothrow_move_constructible<T>::value && std::is_nothrow_move_assignable<T>::value. ) | (since C++11) |
2%29
| noexcept specification: noexcept(noexcept(swap(*a, *b))) | (until C++17) |
|---|---|
| noexcept specification: noexcept(std::is_nothrow_swappable_v<T2>) | (since C++17) |
复杂性
1%29常数
2%29线性在N中
专门性
std::swap可能是专攻命名空间STD对于用户定义的类型，但是这些专门化并不是由ADL%28命名空间std不是用户定义类型%29的关联命名空间。使用户定义的类型可交换的预期方法是在与类型相同的命名空间中提供非成员函数交换：Swappable关于细节。
标准库已经提供了以下重载：
| std::swap(std::pair) (C++11) | specializes the std::swap algorithm (function template) |
|---|---|
| std::swap(std::tuple) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::shared_ptr) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::weak_ptr) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::unique_ptr) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::function) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::basic_string) | specializes the std::swap algorithm (function template) |
| std::swap(std::array) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::deque) | specializes the std::swap algorithm (function template) |
| std::swap(std::forward_list) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::list) | specializes the std::swap algorithm (function template) |
| std::swap(std::vector) | specializes the std::swap algorithm (function template) |
| std::swap(std::map) | specializes the std::swap algorithm (function template) |
| std::swap(std::multimap) | specializes the std::swap algorithm (function template) |
| std::swap(std::set) | specializes the std::swap algorithm (function template) |
| std::swap(std::multiset) | specializes the std::swap algorithm (function template) |
| std::swap(std::unordered_map) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::unordered_multimap) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::unordered_set) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::unordered_multiset) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::queue) | specializes the std::swap algorithm (function template) |
| std::swap(std::priority_queue) | specializes the std::swap algorithm (function template) |
| std::swap(std::stack) | specializes the std::swap algorithm (function template) |
| std::swap(std::valarray) (C++11) | specializes the std::swap() algorithm (function template) |
| std::swap(std::basic_stringbuf) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::basic_istringstream) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::basic_ostringstream) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::basic_stringstream) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::basic_filebuf) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::basic_ifstream) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::basic_ofstream) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::basic_fstream) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::basic_regex) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::match_results) (C++11) | specializes the std::swap() algorithm (function template) |
| std::swap(std::thread) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::unique_lock) (C++11) | specialization of std::swap for unique_lock (function template) |
| std::swap(std::promise) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::packaged_task) (C++11) | specializes the std::swap algorithm (function template) |
| std::swap(std::optional) (C++17) | specializes the std::swap algorithm (function) |
| std::swap(std::any) (C++17) | specializes the std::swap algorithm (function) |
| std::swap(std::variant) (C++17) | specializes the std::swap algorithm (function) |
| swap(std::filesystem::path) | swaps two paths (function) |
例
二次
#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';
}
二次
产出：
二次
5 3
3 5
二次
另见
| iter_swap | swaps the elements pointed to by two iterators (function template) |
|---|---|
| swap_ranges | swaps two ranges of elements (function template) |
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