I'm trying to find out the significance of the difference_type member for the satisfaction of std::weakly_incrementable concept. I'm currently defining a class satisfying std::output_iterator and have nothing in the domain to attach this type to (and struggling to find a use case for it).
I've tracked the root to n3351 paper and yet haven't found the actual reason there. Why did the commitee choose to put it this place in the hierarchy instead of std::input_iterator for example?