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

NAME
     std::uninitialized_move_n - std::uninitialized_move_n

Synopsis
	Defined in header <memory>
	template< class InputIt, class Size, class NoThrowForwardIt >

	std::pair<InputIt,  NoThrowForwardIt>				     (1)
     (since C++17)
	    uninitialized_move_n( InputIt first, Size count,

				  NoThrowForwardIt d_first );
	template< class ExecutionPolicy, class ForwardIt,

		  class Size, class NoThrowForwardIt >
	std::pair<ForwardIt,  NoThrowForwardIt> 			     (2)
     (since C++17)
	    uninitialized_move_n( ExecutionPolicy&& policy, ForwardIt
	first,

				  Size count, NoThrowForwardIt d_first );

	1) Moves count elements from a range beginning at first to an uninitial-
     ized memory
	area  beginning  at  d_first  as  if  by for (; n > 0; ++d_first, (void)
     ++first, --n)
	    ::new (static_cast<void*>(std::addressof(*d_first)))
		typename
	std::iterator_traits<NoThrowForwardIt>::value_type(std::move(*first));
	If an exception is thrown during the  initialization,  some  objects  in
     first + [0, n)
	are  left in a valid but unspecified state, and the objects already con-
     structed are
	destroyed in an unspecified order.

	If d_first + [0, n) overlaps with  first  +  [0,  n),  the  behavior  is
     (since C++20)
	undefined.

	2) Same as (1), but executed according to policy. This overload partici-
     pates in
	overload resolution only if

	std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>    is    true.
     (until
										  C++20)
	std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>      is
     true. (since
										  C++20)

Parameters
	first		   -	      the beginning of the range of the elements
     to move
	d_first 	   -	      the beginning of the destination range
	count		   -	      the number of elements to move
	policy		   -	      the execution policy to use. See execution
     policy for
				      details.

Type requirements
	-
	InputIt must meet the requirements of LegacyInputIterator.
	-
	ForwardIt must meet the requirements of LegacyForwardIterator.
	-
	NoThrowForwardIt must meet the requirements of LegacyForwardIterator.
	-
	No  increment,	assignment, comparison, or indirection through valid in-
     stances of
	NoThrowForwardIt may throw exceptions.

Return value
	A pair whose first element is an iterator to the element past  the  last
     element moved
	in the source range, and whose second element is an iterator to the ele-
     ment past the
	last element moved in the destination range.

Complexity
	Linear in count.

Exceptions
	The overload with a template parameter named ExecutionPolicy reports er-
     rors as
	follows:

	  *  If  execution of a function invoked as part of the algorithm throws
     an exception
	    and ExecutionPolicy is one of the standard policies,  std::terminate
     is called.
	    For  any  other  ExecutionPolicy, the behavior is implementation-de-
     fined.
	  * If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Possible implementation
     template<class InputIt, class Size, class	NoThrowForwardIt>  std::pair<In-
     putIt, NoThrowForwardIt>
	 uninitialized_move_n(InputIt	first,	 Size	count,	NoThrowForwardIt
     d_first) {
	 using	   Value     =	   typename	std::iterator_traits<NoThrowFor-
     wardIt>::value_type;
	 NoThrowForwardIt current = d_first;
	 try
	 {
	     for (; count > 0; ++first, (void) ++current, --count)
		 ::new		  (static_cast<void*>(std::addressof(*current)))
     Value(std::move(*first));
	 }
	 catch (...)
	 {
	     std::destroy(d_first, current);
	     throw;
	 }
	 return {first, current}; }

Example
     // Run this code

      #include <cstdlib>
      #include <iomanip>
      #include <iostream>
      #include <memory>
      #include <string>

      void print(auto rem, auto first, auto last)
      {
	  for (std::cout << rem; first != last; ++first)
	      std::cout << std::quoted(*first) << ' ';
	  std::cout << '\n';
      }

      int main()
      {
	  std::string in[]{"One", "Definition", "Rule"};
	  print("initially, in: ", std::begin(in), std::end(in));

	  if (
	      constexpr auto sz = std::size(in);
	      void*	out	 =	std::aligned_alloc(alignof(std::string),
     sizeof(std::string) * sz))
	  {
	      try
	      {
		  auto first{static_cast<std::string*>(out)};
		  auto last{first + sz};
		  std::uninitialized_move_n(std::begin(in), sz, first);

		  print("after move, in: ", std::begin(in), std::end(in));
		  print("after move, out: ", first, last);

		  std::destroy(first, last);
	      }
	      catch (...)
	      {
		  std::cout << "Exception!\n";
	      }
	      std::free(out);
	  }
      }

Possible output:
      initially, in: "One" "Definition" "Rule"
      after move, in: "" "" ""
      after move, out: "One" "Definition" "Rule"

	Defect reports

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

	   DR	 Applied to		 Behavior as published		    Cor-
     rect behavior
	LWG 3870 C++20	    this algorithm might create objects on a const  kept
     disallowed
			    storage

See also
	uninitialized_move	     moves a range of objects to  an  uninitial-
     ized area of
	(C++17) 		     memory
				     (function template)
	uninitialized_copy_n	     copies a number of objects to an uninitial-
     ized area of
	(C++11) 		     memory
				     (function template)
	ranges::uninitialized_move_n  moves a number of objects to an uninitial-
     ized area of
	(C++20) 		     memory
				     (niebloid)

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