Re: iterate over vector in leaps

Baruch Burstein <bmburstein@gmail.com> wrote:


Here, this should get you started:

template < typename Container >
class jump_iterator : public iterator<forward_iterator_tag,
vector<int>::value_type> {
   Container* container;
   typename Container::iterator it;
   int step;
public:
   jump_iterator(Container& c, typename Container::iterator i,
                                                         int s = 0):
      container(&c), it(i), step(s) { }
   
   bool operator==(const jump_iterator& rhs) const {
      return it == rhs.it;
   }
   
   jump_iterator& operator++() {
      for (int i = 0; i < step && it != container->end(); ++i)
         ++it;
      return *this;
   }
   
   jump_iterator operator++(int) {
      jump_iterator result = *this;
      ++(*this);
      return result;
   }
   
   reference operator*() { return *it; }
};

template < typename Container >
bool operator!=(const jump_iterator<Container>& lhs, const
jump_iterator<Container>& rhs) {
   return !(lhs == rhs);
}

template < typename Container >
jump_iterator<Container> jump_iterator_begin(Container& c, int s) {
   return jump_iterator<Container>(c, c.begin(), s);
}

template < typename Container >
jump_iterator<Container> jump_iterator_end(Container& c) {
   return jump_iterator<Container>(c, c.end());
}

use the above like this:

void fn(vector<int>& vec) {
   copy(jump_iterator_begin(vec, 3), jump_iterator_end(vec),
                                    ostream_iterator<int>(cout, " "));
}