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std:: incrementable_traits <std::common_iterator>

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Iterator library
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(C++20)
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(C++20)
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(C++17)
std::common_iterator
Defined in header <iterator>
template < class I, class S >

struct incrementable_traits < std:: common_iterator < I, S >> {
using difference_type = std:: iter_difference_t < I > ;

} ;
(since C++20)

Provides the uniform interface to the associated difference type of the std::common_iterator type.

Example

Run this code 
#include <cstddef>
#include <iterator>
#include <list>
#include <string>
#include <type_traits>
int main()
{
    using CI = std::common_iterator<
                   std::counted_iterator<int*>,
                   std::default_sentinel_t>;
    using CL = std::common_iterator<
                   std::counted_iterator<std::list<std::string>::iterator>,
                   std::default_sentinel_t>;
    CL cl{std::default_sentinel};
    static_assert(
        std::same_as<std::incrementable_traits<CI>::difference_type, std::ptrdiff_t> &&
        std::same_as<std::incrementable_traits<CL>::difference_type, std::ptrdiff_t> &&
        std::same_as<std::incrementable_traits<decltype(cl)>::difference_type,
                     std::ptrdiff_t>);
}

See also

(C++20)
computes the difference type of a weakly_incrementable type
(class template)
(C++20) (C++20) (C++23) (C++20) (C++20) (C++20)
computes the associated types of an iterator
(alias template)
(C++20)
provides uniform interface to the properties of the std::common_iterator type
(class template specialization)