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std::unorde...ltiset::swap(3) C++ Standard Libarystd::unorde...ltiset::swap(3)

NAME
       std::unordered_multiset::swap - std::unordered_multiset::swap

Synopsis
	  void	       swap(	    unordered_multiset&	       other	    );
       (since C++11)
									     (un-
       til C++17)
	  void swap( unordered_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 past-the-end iterator
       is invalidated.

	  The Hash and KeyEqual	objects	must be	Swappable, and	they  are  ex-
       changed using
	  unqualified calls 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_alloca-
       tor() !=	  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 Hash	or  KeyEqual  objects.
       (until C++17)
	  noexcept specification:
	  noexcept(std::allocator_traits<Allocator>::is_always_equal::value
									    (since
       C++17)
	  && std::is_nothrow_swappable<Hash>::value

	  && std::is_nothrow_swappable<key_equal>::value)

Complexity
	  Constant.

Example
       // Run this code

	#include <iostream>
	#include <unordered_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::unordered_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 con-
       tainer before the swap
	    // refers to the same element in the  other	 container  after  the
       swap. Same is true
	    // for references.
	}

Possible output:
	{ 2 3 3	1 } { 4	5 5 } 3	5 2 4
	{ 4 5 5	} { 2 3	3 1 } 3	5 2 4

See also
	  std::swap(std::unordered_multiset)  specializes  the std::swap algo-
       rithm
	  (C++11)			     (function template)

http://cppreference.com		  2022.07.31	 std::unorde...ltiset::swap(3)

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