nth_iterator - an iterator wrapper that only uses every nth element returned by the underlying iterator

nth_iterator.hpp

template <int n, typename Iterator>
class nth_iterator
{
public:
  typedef typename std::iterator_traits<Iterator>::iterator_category iterator_category;
  typedef typename std::iterator_traits<Iterator>::value_type value_type;
  typedef typename std::iterator_traits<Iterator>::difference_type difference_type;
  typedef typename std::iterator_traits<Iterator>::pointer pointer;
  typedef typename std::iterator_traits<Iterator>::reference reference;
  typedef Iterator iterator_type;

  nth_iterator() {}
  nth_iterator(const iterator_type& it)
    : _it(it) {}
  nth_iterator& operator++() { for (int i=0; i<n; ++i) ++_it; return *this;}
  nth_iterator operator++(int) { this_type ret(*this); for (int i=0; i<n; ++i) ++_it; return ret;}
  reference operator*() { return *_it; }
  template <int m, typename Iterator2>
  bool operator==(const nth_iterator<m, Iterator2>& other) { return _it == other._it; }
  template <int m, typename Iterator2>
  bool operator!=(const nth_iterator<m, Iterator2>& other) { return _it != other._it; }

private:
  typedef nth_iterator<n, Iterator> this_type;
  iterator_type _it;
};