std::incrementable_traits(3)

NAME
std::incrementable_traits - std::incrementable_traits

Synopsis
   Defined in header <iterator>
   template< class I, class S >
   struct incrementable_traits<std::common_iterator<I, S>> { (since C++20)
   using difference_type = std::iter_difference_t<I>;
   };
   Provides the uniform interface to the associated difference type of the
   std::common_iterator type.

Example
// Run this code
 #include <list>
 #include <string>
 #include <cstddef>
 #include <iterator>
 #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
   incrementable_traits computes the difference type of a
   (C++20) weakly_incrementable type
                        (class template)
   iter_value_t
   iter_reference_t
   iter_const_reference_t
   iter_difference_t
   iter_rvalue_reference_t computes the associated types of an
   iter_common_reference_t iterator
   (C++20) (alias template)
   (C++20)
   (C++23)
   (C++20)
   (C++20)
   (C++20)
                        provides uniform interface to the
   std::iterator_traits<std::common_iterator> properties of the std::common_iterator
   (C++20) type
                        (class template specialization)