std::pair<T1,T2>::swap (3) - Linux Manuals

std::pair<T1,T2>::swap: std::pair<T1,T2>::swap

NAME

std::pair<T1,T2>::swap - std::pair<T1,T2>::swap

Synopsis

void swap(pair& other) noexcept(/* see below */); (since C++11)
                                                             (until C++20)
constexpr void swap(pair& other) noexcept(/* see below */); (since C++20)

Swaps first with other.first and second with other.second.

Parameters

other - pair of values to swap

Return value

(none)

Exceptions

noexcept specification:
noexcept(
noexcept(swap(first, other.first)) && (until C++17)
noexcept(swap(second, other.second))
)
In the expression above, the identifier swap is looked up in the same manner as the one used by the C++17 std::is_nothrow_swappable trait.
noexcept specification:
noexcept(
std::is_nothrow_swappable_v<first_type> && (since C++17)
std::is_nothrow_swappable_v<second_type>
)

Example

// Run this code

  #include <iostream>
  #include <utility>
  #include <string>
  int main()
  {
      std::pair<int, std::string> p1, p2;
      p1 = std::make_pair(10, "test");
      p2.swap(p1);
      std::cout << "(" << p2.first << ", " << p2.second << ")\n";
  }

Output:

  (10, test)

Defect reports

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 the noexcept specification is ill-formed made to work