std::counted_iterator::counted_iterator - cppreference.com (original) (raw)

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.

  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-initialized I also have defined behavior.

  2. The underlying iterator is initialized with std::move(x) and the underlying length is initialized with n. The behavior is undefined if n is negative.

  3. The underlying iterator and length are initialized with those of other.

[edit] Parameters

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

[edit] Example

#include #include #include #include   int main() { static constexpr auto pi = {3, 1, 4, 1, 5, 9, 2};   // (1) default constructor: constexpr std::counted_iterator<std::initializer_list::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::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::iterator> i3{i2};   std::ranges::copy(i3, std::default_sentinel, std::ostream_iterator{std::cout, " "}); }

Output:

[edit] See also