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std::counte...ted_iterator(3)  C++ Standard Libary std::counte...ted_iterator(3)

NAME
     std::counted_iterator::counted_iterator	    -	     std::counted_itera-
     tor::counted_iterator

Synopsis
	constexpr counted_iterator()  requires				     (1)
     (since C++20)
	std::default_initializable<I> = default;
	constexpr  counted_iterator(  I x, std::iter_difference_t<I> n );    (2)
     (since C++20)
	template< class I2 >

	    requires std::convertible_to<const I2&,  I> 		     (3)
     (since C++20)

		constexpr counted_iterator( const counted_iterator<I2>&
	other );

	Constructs a new iterator adaptor.

	1)  Default  constructor.  Value-initializes the underlying iterator and
     initialized
	the underlying length with 0. Operations on the resulting iterator  have
     defined
	behavior if and only if the corresponding operations on a value-initial-
     ized I also
	have defined behavior.
	2)  The underlying iterator is initialized with std::move(x) and the un-
     derlying
	length is initialized with n. The behavior is undefined if  n  is  nega-
     tive.
	3)  The  underlying  iterator  and  length are initialized with those of
     other.

Parameters
	x     - iterator to adapt
	n     - distance to the end
	other - iterator adaptor to convert

Example
     // Run this code

      #include <algorithm>
      #include <initializer_list>
      #include <iostream>
      #include <iterator>

      int main()
      {
	  static constexpr auto pi = {3, 1, 4, 1, 5, 9, 2};

	  // (1) default constructor:
	  constexpr  std::counted_iterator<std::initializer_list<int>::iterator>
     i1{};
	  static_assert(i1 == std::default_sentinel);
	  static_assert(i1.count() == 0);

	  // (2) initializes the iterator and length respectively:
	  constexpr  std::counted_iterator<std::initializer_list<int>::iterator>
     i2{
	      pi.begin(), pi.size() - 2
	  };
	  static_assert(i2.count() == 5);
	  static_assert(*i2 == 3 && i2[1] == 1);

	  // (3) converting-constructor:
	  std::counted_iterator<std::initializer_list<const	 int>::iterator>
     i3{i2};

	  std::ranges::copy(i3, std::default_sentinel,
	      std::ostream_iterator<const int>{std::cout, " "});
      }

Output:
      3 1 4 1 5

See also
	operator= assigns another iterator adaptor
	(C++20)   (public member function)

http://cppreference.com 	   2024.06.10	   std::counte...ted_iterator(3)
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