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

NAME
       std::set::swap -	std::set::swap

Synopsis
	  void swap( set& other	);			      (until C++17)
	  void swap( set& 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 in-
       validated.

	  The Compare objects must be Swappable, and they are exchanged	 using
       unqualified 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_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   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::set<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.

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

	    std::set<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	} { 4 5	} 2 5 1	4
	{ 4 5 }	{ 1 2 3	} 2 5 1	4
	{ 1 2 }	{ 3 4 }	6 9
	{ 3 4 }	{ 1 2 }	9 6

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

Category:
	    * conditionally noexcept

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

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