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std::counted_iterator<I>::counted_iterator

From cppreference.com
 
 
Iterator library
Iterator concepts
Iterator primitives
Algorithm concepts and utilities
Indirect callable concepts
Common algorithm requirements
(C++20)
(C++20)
(C++20)
Utilities
(C++20)
Iterator adaptors
Iterator customization points
Iterator operations
(C++11)    
(C++11)
Range access
(C++11)(C++14)
(C++14)(C++14)    
(C++11)(C++14)
(C++14)(C++14)    
(C++17)(C++20)
(C++17)
(C++17)
 
 
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 <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

[edit] See also

(C++20)
assigns another iterator adaptor
(public member function) [edit]