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std::multiset::swap(3)	       C++ Standard Libary	  std::multiset::swap(3)

NAME
     std::multiset::swap - std::multiset::swap

Synopsis
	void swap( multiset& other );				 (until C++17)
	void swap( multiset& other ) noexcept(/* see below */);  (since C++17)

	Exchanges  the	contents  of the container with those of other. Does not
     invoke any
	move, copy, or swap operations on individual elements.

	All iterators and references remain valid. The end() iterator is invali-
     dated.

	The Compare objects must be Swappable, and they are exchanged using  un-
     qualified call
	to non-member swap.

	If		std::allocator_traits<allocator_type>::propagate_on_con-
     tainer_swap::value
	is true, then the allocators are exchanged using an unqualified call  to
     (since
	non-member swap. Otherwise, they are not swapped (and if get_allocator()
     !=   C++11)
	other.get_allocator(), the behavior is undefined).

Parameters
	other - container to exchange the contents with

Return value
	(none)

Exceptions
	Any exception thrown by the swap of the Compare objects.	  (until
     C++17)
	noexcept specification:
	noexcept(std::allocator_traits<Allocator>::is_always_equal::value (since
     C++17)
	&& std::is_nothrow_swappable<Compare>::value)

Complexity
	Constant.

Example
     // Run this code

      #include <functional>
      #include <iostream>
      #include <set>

      template<class Os, class Co>
      Os& operator<<(Os& os, const Co& co)
      {
	  os << '{';
	  for (auto const& i : co)
	      os << ' ' << i;
	  return os << " } ";
      }

      int main()
      {
	  std::multiset<int> a1{3, 1, 3, 2}, a2{5, 4, 5};

	  auto it1 = std::next(a1.begin());
	  auto it2 = std::next(a2.begin());

	  const int& ref1 = *(a1.begin());
	  const int& ref2 = *(a2.begin());

	  std::cout  << a1 << a2 << *it1 << ' ' << *it2 << ' ' << ref1 << ' ' <<
     ref2 << '\n';
	  a1.swap(a2);
	  std::cout << a1 << a2 << *it1 << ' ' << *it2 << ' ' << ref1 << ' '  <<
     ref2 << '\n';

	  //  Note  that every iterator referring to an element in one container
     before the swap
	  // refers to the same element in the other container after  the  swap.
     Same is true
	  // for references.

	  struct Cmp : std::less<int>
	  {
	      int id{};
	      Cmp(int i) : id{i} {}
	  };

	  std::multiset<int,  Cmp>  s1{{2,  2,	1, 1}, Cmp{6}}, s2{{4, 4, 3, 3},
     Cmp{9}};

	  std::cout << s1 << s2 << s1.key_comp().id << ' '  <<	s2.key_comp().id
     << '\n';
	  s1.swap(s2);
	  std::cout  <<  s1 << s2 << s1.key_comp().id << ' ' << s2.key_comp().id
     << '\n';

	  // So, comparator objects (Cmp) are also exchanged after the swap.
      }

Output:
      { 1 2 3 3 } { 4 5 5 } 2 5 1 4
      { 4 5 5 } { 1 2 3 3 } 2 5 1 4
      { 1 1 2 2 } { 3 3 4 4 } 6 9
      { 3 3 4 4 } { 1 1 2 2 } 9 6

See also
	std::swap(std::multiset) specializes the std::swap algorithm
				 (function template)

Category:
	  * conditionally noexcept

http://cppreference.com 	   2024.06.10		  std::multiset::swap(3)
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