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std::iter_swap(3)	       C++ Standard Libary	       std::iter_swap(3)

NAME
     std::iter_swap - std::iter_swap

Synopsis
	Defined in header <algorithm>
	template< class ForwardIt1, class ForwardIt2 >	(constexpr since C++20)
	void iter_swap( ForwardIt1 a, ForwardIt2 b );

	Swaps the values of the elements the given iterators are pointing to.

	If  any  of the following conditions is satisfied, the behavior is unde-
     fined:

	  * a or b is not dereferenceable.
	  * *a is not Swappable with *b.

Parameters
	a, b		 -	       iterators to the elements to swap

Type requirements
	-
	ForwardIt1, ForwardIt2 must meet the requirements of LegacyForwardItera-
     tor.

Return value
	(none)

Complexity
	Constant.

Notes
	This function template models the semantics of the swap operation  given
     by
	Swappable.  That is, overloads of swap found by ADL and the fall back of
     std::swap
	are considered.

Possible implementation
	template<class ForwardIt1, class ForwardIt2>
	constexpr //< since C++20
	void iter_swap(ForwardIt1 a, ForwardIt2 b)
	{
	    using std::swap;
	    swap(*a, *b);
	}

Example
	The following is an implementation of selection sort in C++.

     // Run this code

      #include <algorithm>
      #include <iostream>
      #include <random>
      #include <string_view>
      #include <vector>

      template<class ForwardIt>
      void selection_sort(ForwardIt begin, ForwardIt end)
      {
	  for (ForwardIt it = begin; it != end; ++it)
	      std::iter_swap(it, std::min_element(it, end));
      }

      void println(std::string_view rem, std::vector<int> const& v)
      {
	  std::cout << rem;
	  for (int e : v)
	      std::cout << e << ' ';
	  std::cout << '\n';
      }

      template<int min, int max>
      int rand_int()
      {
	  static std::uniform_int_distribution dist(min, max);
	  static std::mt19937 gen(std::random_device{}());
	  return dist(gen);
      }

      int main()
      {
	  std::vector<int> v;
	  std::generate_n(std::back_inserter(v), 20, rand_int<-9, +9>);

	  std::cout << std::showpos;
	  println("Before sort: ", v);
	  selection_sort(v.begin(), v.end());
	  println("After sort:	", v);
      }

Possible output:
      Before sort: -9 -3 +2 -8 +0 -1 +8 -4 -5 +1 -4 -5 +4 -9 -8 -6 -6 +8 -4 -6
      After sort:  -9 -9 -8 -8 -6 -6 -6 -5 -5 -4 -4 -4 -3 -1 +0 +1 +2 +4 +8 +8

	Defect reports

	The following behavior-changing defect	reports  were  applied	retroac-
     tively to
	previously published C++ standards.

	  DR	 Applied  to	  Behavior as published 	     Correct be-
     havior
	LWG 187 C++98	   it was unspecified whether swap the effect is equiva-
     lent to
			   is used			   swap(*a, *b)

See also
	swap	    swaps the values of two objects
		    (function template)
	swap_ranges swaps two ranges of elements
		    (function template)
	iter_swap   swaps the objects pointed to by two adjusted underlying  it-
     erators
	(C++20)     (function template)
	iter_swap   swaps the objects pointed to by two underlying iterators
	(C++20)     (function template)
	iter_swap   swaps the values referenced by two dereferenceable objects
	(C++20)     (customization point object)

http://cppreference.com 	   2024.06.10		       std::iter_swap(3)
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