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std::common...mon_iterator(3)  C++ Standard Libary std::common...mon_iterator(3)

NAME
     std::common_iterator::common_iterator - std::common_iterator::common_itera-
     tor

Synopsis
	constexpr  common_iterator()  requires std::default_initializable<I> (1)
     (since C++20)
	= default;
	constexpr common_iterator( I i	);				     (2)
     (since C++20)
	constexpr  common_iterator(  S s );				     (3)
     (since C++20)
	template< class I2, class S2 >

	requires std::convertible_to<const I2&, I>  &&			     (4)
     (since C++20)
		 std::convertible_to<const S2&, S>

	constexpr common_iterator( const common_iterator<I2, S2>& x );

	Constructs  a new iterator adaptor, effectively initializes the underly-
     ing
	std::variant<I, S> member object var to hold an I (iterator) or S  (sen-
     tinel) object.

	1) Default constructor. Default-initializes var. After construction, var
     holds a
	value-initialized I object. Operations on the resulting iterator adaptor
     have
	defined behavior if and only if the corresponding operations on a value-
     initialized
	I also have defined behavior.
	2) After construction, var holds an I object move-constructed from i.
	3) After construction, var holds an S object move-constructed from s.
	4)  After  construction, var holds an I or S object initialized from the
     I2 or S2 held
	by x.var, if x.var holds that alternative, respectively. The behavior is
     undefined
	if x is in an invalid state, that is, x.var.valueless_by_exception()  is
     equal to
	true.

Parameters
	i - iterator to adapt
	s - sentinel to adapt
	x - iterator adaptor to copy

Example
     // Run this code

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

      int main()
      {
	  std::vector v{3, 1, 4, 1, 5, 9, 2};

	  using CI = std::common_iterator<
			 std::counted_iterator<std::vector<int>::iterator>,
			 std::default_sentinel_t>;
	  CI unused; // (1)
	  CI start{std::counted_iterator{std::next(begin(v)), ssize(v) - 2}}; //
     (2)
	  CI finish{std::default_sentinel}; // (3)
	  CI first{start}; // (4)
	  CI last{finish}; // (4)

	  std::copy(first, last, std::ostream_iterator<int>{std::cout, " "});
	  std::cout << '\n';

	  std::common_iterator<
	      std::counted_iterator<
		  std::ostream_iterator<double>>,
		  std::default_sentinel_t>
		  beg{std::counted_iterator{std::ostream_iterator<dou-
     ble>{std::cout,";	"}, 5}},
		  end{std::default_sentinel};
	  std::iota(beg, end, 3.1);
	  std::cout << '\n';
      }

Output:
      1 4 1 5 9
      3.1;  4.1;  5.1;	6.1;  7.1;

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

http://cppreference.com 	   2024.06.10	   std::common...mon_iterator(3)
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