NAME¶

std::common_iterator::common_iterator - std::common_iterator::common_iterator

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 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¶

// 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<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;

See also¶

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