constexpr counted_iterator() requires std::default_initializable<I> = default; | (1) | (since C++20) |
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> constexpr counted_iterator( const counted_iterator<I2>& other ); | (3) | (since C++20) |
Constructs a new iterator adaptor.
0
. Operations on the resulting iterator have defined behavior if and only if the corresponding operations on a value-initialized I
also have defined behavior.std::move(x)
and the underlying length is initialized with n
. The behavior is undefined if n
is negative.other
.x | - | iterator to adapt |
n | - | distance to the end |
other | - | iterator adaptor to convert |
#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
(C++20) | assigns another iterator adaptor (public member function) |
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