#include <boost/multi_index_container.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/enable_shared_from_this.hpp>
#include <iostream>

typedef int handle;
typedef int group_id;


struct NodeBase:boost::enable_shared_from_this<NodeBase>
{

 virtual ~NodeBase(){}

 virtual group_id memberOf()const=0;
 virtual handle   getHandle()const=0;
};

struct NodeType:NodeBase
{
 NodeType(handle h,group_id gid):h(h),gid(gid){}


 virtual group_id memberOf()const{return gid;}
 virtual handle   getHandle()const{return h;}


private:
 group_id gid;
 handle   h;
};


struct NodeBaseHandleExtractor
{
 typedef handle result_type;
 result_type operator()(const boost::shared_ptr<NodeBase>& x) const
 {
   return x->getHandle();
 }
};

struct NodeBaseGroupIdExtractor
{
 typedef group_id result_type;
 result_type operator()(const boost::shared_ptr<NodeBase>& x) const
 {
   return x->memberOf();

 }
};

typedef boost::multi_index::multi_index_container<
 boost::shared_ptr<NodeBase>,
 boost::multi_index::indexed_by<
   boost::multi_index::ordered_unique<

     NodeBaseHandleExtractor

   >,
   boost::multi_index::ordered_non_unique<

     NodeBaseGroupIdExtractor

   >
 >
> NodePtrSet;

int main()
{
 NodePtrSet ns;

 typedef boost::shared_ptr<NodeBase> element_type;

 ns.insert(element_type(new NodeType(0,10))); // 0 = id, 10 = group_id
 ns.insert(element_type(new NodeType(1,10)));
 ns.insert(element_type(new NodeType(2,20)));

 typedef boost::multi_index::nth_index<NodePtrSet,1>::type index_t;
 const index_t& i=boost::multi_index::get<1>(ns);
 
 for(index_t::const_iterator it=i.begin();it!=i.end();){ 
   std::cout<<i.key_extractor()(*it)<<std::endl;
   it=i.upper_bound(i.key_extractor()(*it));
  }

 return 0;
}