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

NAME
     std::counted_iterator - std::counted_iterator

Synopsis
	Defined in header <iterator>
	template< std::input_or_output_iterator I >  (since C++20)
	class counted_iterator;

	std::counted_iterator  is an iterator adaptor which behaves exactly like
     the
	underlying iterator, except that it keeps track of the distance  to  the
     end of its
	range.	This  iterator	is equal to std::default_sentinel if and only if
     its count
	reaches zero.

Member types
	Member type	  Definition
	iterator_type	  I
	value_type	  std::iter_value_t<I> if I models  indirectly_readable;
     otherwise,
			  not defined
	difference_type   std::iter_difference_t<I>
	iterator_concept  I::iterator_concept if present; otherwise, not defined
	iterator_category  I::iterator_category  if  present; otherwise, not de-
     fined

Member objects
	Member name	  Definition
	current (private) the underlying iterator which base() accesses
			  (exposition-only member object*)
			  the distance between the underlying iterator	and  the
     end of its
	length (private)  range
			  (exposition-only member object*)

Member functions
	constructor	constructs a new iterator adaptor
	(C++20) 	(public member function)
	operator=	assigns another iterator adaptor
	(C++20) 	(public member function)
	base		accesses the underlying iterator
	(C++20) 	(public member function)
	count		returns the distance to the end
	(C++20) 	(public member function)
	operator*	accesses the pointed-to element
	operator->	(public member function)
	(C++20)
	operator[]	accesses an element by index
	(C++20) 	(public member function)
	operator++
	operator++(int)
	operator+=
	operator+	advances or decrements the iterator
	operator--	(public member function)
	operator--(int)
	operator-=
	operator-
	(C++20)

Non-member functions
	operator==			   compares the distances to the end
	operator<=>			   (function template)
	(C++20)
	operator==(std::default_sentinel)   checks if the distance to the end is
     equal to 0
	(C++20) 			   (function template)
	operator+			   advances the iterator
	(C++20) 			   (function template)
	operator-			   computes the distance between two it-
     erator
	(C++20) 			   adaptors
					   (function template)
	operator-(std::default_sentinel_t) computes the signed distance  to  the
     end
	(C++20) 			   (function template)
	iter_move			   casts the result of dereferencing the
     underlying
	(C++20) 			    iterator  to  its  associated rvalue
     reference type
					   (function)
	iter_swap			   swaps the objects pointed to  by  two
     underlying
	(C++20) 			   iterators
					   (function template)

Helper classes
						    provides  uniform  interface
     to the
	std::iterator_traits<std::counted_iterator>    properties     of     the
     std::counted_iterator
	(C++20) 				    type
						    (class  template specializa-
     tion)

Example
     // Run this code

      #include <algorithm>
      #include <iostream>
      #include <iterator>
      #include <string>
      #include <vector>

      using std::operator""s;

      void print(auto const remark, auto const& v)
      {
	  const auto size = std::ssize(v);
	  std::cout << remark << '[' << size << "] { ";
	  for (auto it = std::counted_iterator{std::cbegin(v), size};
	       it != std::default_sentinel; ++it)
	      std::cout << *it << (it.count() > 1 ? ", " : " ");
	  std::cout << "}\n";
      }

      int main()
      {
	  const auto src = {"Arcturus"s,  "Betelgeuse"s,  "Canopus"s,  "Deneb"s,
     "Elnath"s};
	  print("src", src);
	  std::vector<decltype(src)::value_type> dst;
	  std::ranges::copy(std::counted_iterator{src.begin(), 3},
			    std::default_sentinel,
			    std::back_inserter(dst));
	  print("dst", dst);
      }

Output:
      src[5] { Arcturus, Betelgeuse, Canopus, Deneb, Elnath }
      dst[3] { Arcturus, Betelgeuse, Canopus }

	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
			   member  typedefs are not provided member typedefs are
     added to
			   std::incrementable_traits	    account  for  itera-
     tor_traits fix
	P2259R1 C++20	   is specialized for		    redundant
			   counted_iterator			     std::incre-
     mentable_traits
							    specialization    is
     removed

See also
	default_sentinel_t default sentinel for use with iterators that know the
     bound of
	(C++20) 	   their range
			   (class)
	views::counted	   creates a subrange from an iterator and a count
	(C++20) 	   (customization point object)
	ranges::take_view   a view consisting of the first N elements of another
     view
	views::take	   (class template) (range adaptor object)
	(C++20)

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