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std::common_iterator<I,S>::common_iterator

constexpr common_iterator() requires std::default_initializable<I> = default;	(1)	(since C++20)
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> && std::convertible_to<const S2&, S> constexpr common_iterator( const common_iterator<I2, S2>& x );	(4)	(since C++20)

Constructs a new iterator adaptor, effectively initializes the underlying std::variant<I, S> member object var to hold an I (iterator) or S (sentinel) 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

#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<double>{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;

std::common_iterator<I,S>::common_iterator

Parameters

Example

See also