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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 un-
       defined:

	    * 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 LegacyFor-
       wardIterator.

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
       behavior
	  LWG 187 C++98	     it	was unspecified	whether	 swap  the  effect  is
       equivalent 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
       iterators
	  (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  ob-
       jects
	  (C++20)     (customization point object)

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

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