Наследование стандартного итератора

#include <iostream>
#include <vector>
#include <boost/iterator/iterator_adaptor.hpp>
 
template<typename Predicate, typename Iterator>
struct filter_iterator : 
   public boost::iterators::iterator_adaptor
   <
      filter_iterator<Predicate, Iterator>,
      Iterator
   >
{
   friend class boost::iterators::iterator_core_access;
   typedef boost::iterators::iterator_adaptor
   <
      filter_iterator<Predicate, Iterator>,
      Iterator
   > base_type;
public:
   filter_iterator(Predicate p, Iterator b, Iterator e) :
      base_type(b), pred(p), end(e)
   {
      satisfy_predicate();
   }
private:
   void increment()
   {
      ++(this->base_reference());
      satisfy_predicate();
   }
 
   /*void decrement()
   {
      while (!pred(*--(this->base_reference())));
   }*/
 
   void satisfy_predicate()
   {
      while (this->base() != end && !pred(*this->base()))
      {
         ++(this->base_reference());
      }
   }
 
   Predicate pred;
   Iterator end;
};
 
template<typename Predicate, typename Iterator>
filter_iterator<Predicate, Iterator> make_filter_iterator(const Predicate& pred, const Iterator& b, const Iterator& e)
{
   return filter_iterator<Predicate, Iterator>(pred, b, e);
}

int main()
{
   std::vector<int> v = {-1,2,3,-4,5};
   auto pred = [](int v) { return v > 0; };
   auto f_begin = make_filter_iterator(pred, v.begin(), v.end()),
        f_end = make_filter_iterator(pred, v.end(), v.end());
   while (f_begin != f_end)
   {
      std::cout << *f_begin << std::endl;
      ++f_begin;
   }
}