How to write a C++ custom iterator(which can used in std::distance ...).

iterator.cpp

#include <iterator>
#include <cstdio>

// A number interator
struct MyIterator {
        using value_type = int;
        using size_type = std::size_t;
        using difference_type = std::ptrdiff_t;
        using reference = int&;

        value_type value;
        MyIterator(value_type value): value{value} {}
        MyIterator &operator ++() {
                value += 1;
                return *this;
        }
        reference operator *() {
                return value;
        }
        reference operator ->() {
                return value;
        }
        bool operator==(const MyIterator &other) { return value == other.value; }
        bool operator !=(const MyIterator &other) { return !((*this) == other); }
};

// the following lines are needed to implement std::iterator_traits, used in std::distance()
template <> struct std::iterator_traits<MyIterator>
{
        using difference_type = MyIterator::difference_type;
        using value_type = MyIterator::value_type;
        using reference = MyIterator::reference;
        using iterator_category = std::forward_iterator_tag;
};


int main() {
        MyIterator Begin = 1;
        MyIterator End = 10000;
        printf("distance(a, b) = %zu\n", std::distance(Begin, End));
}