Python's range in C++11

#include <cstdlib>
#include <iostream>

#define in :

class range
{
    public:

        constexpr range(int end):
            _i(0),
            _end(end),
            _step(1),
            _sup(end >= 0)
        {}

        constexpr range(int begin, int end, unsigned int step=1):
            _i(begin),
            _end(end),
            _step(step),
            _sup(end >= begin)
        {}

        constexpr const range& begin()
        {
            return *this;
        }

        constexpr const range& end()
        {
            return *this;
        }

        constexpr bool operator!=(const range&)
        {
            return _sup ? (_i < _end) : (_i > _end);
        }

        void operator++()
        {
            if (_sup)
            {
                _i += _step;
            }
            else
            {
                _i -= _step;
            }
        }

        constexpr const int& operator*()
        {
            return _i;
        }

    private:

        int _i;
        const int _end;
        const unsigned int _step;
        const bool _sup;
};



int main()
{
    for (const int& i in range(20, -20, 5))
    {
        std::cout << i << std::endl;
        if (i == 30) break;
    }

    return EXIT_SUCCESS;
}