std::incrementable_traits<std::common_iterator>

Since C++20

Header: <iterator>

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

# Declarations

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

(since C++20)

# Example

#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