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| Member functions | ||||
pair::swap (C++11) | ||||
| Non-member functions | ||||
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20) | ||||
(C++11) | ||||
(C++11) | ||||
| Helper classes | ||||
(C++11) | ||||
(C++11) | ||||
(C++23) | ||||
(C++23) | ||||
(C++11) | ||||
| Deduction guides(C++17) |
| (1) | ||
void swap( pair& other)noexcept(/* see below */); | (since C++11) (until C++20) | |
constexprvoid swap( pair& other)noexcept(/* see below */); | (since C++20) | |
constexprvoid swap(const pair& other)constnoexcept(/* see below */); | (2) | (since C++23) |
Swapsfirst withother.first andsecond withother.second, as if byusingstd::swap; swap(first, other.first); swap(second, other.second);.
If either selected | (until C++23) |
2) The program is ill-formed if eitherstd::is_swappable_v<const T1> orstd::is_swappable_v<const T2> is nottrue. If either selected | (since C++23) |
Contents |
| other | - | pair of values to swap |
(none)
noexcept specification: noexcept( noexcept(swap(first, other.first))&& In the expression above, the identifier | (until C++17) |
1) noexcept specification: noexcept( std::is_nothrow_swappable_v<first_type>&& 2) noexcept specification: noexcept( std::is_nothrow_swappable_v<const first_type>&& | (since C++17) |
#include <iostream>#include <utility>#include <string>int main(){std::pair<int,std::string> p1(10,"test"), p2; p2.swap(p1);std::cout<<"("<< p2.first<<", "<< p2.second<<")\n"; #if __cpp_lib_ranges_zip >= 202110L// Using the C++23 const qualified swap overload// (swap is no longer propagating pair constness)int i1=10, i2{};std::string s1("test"), s2;conststd::pair<int&,std::string&> r1(i1, s1), r2(i2, s2); r2.swap(r1);std::cout<<"("<< i2<<", "<< s2<<")\n";#endif}
Possible output:
(10, test)(10, test)
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 2456 | C++11 | thenoexcept specification is ill-formed | made to work |
| swaps the values of two objects (function template)[edit] | |
swaps the contents of twotuples(public member function of std::tuple<Types...>)[edit] |
