typedef boost::shared_ptr< param > ParamPtr;
typedef std::vector< ParamPtr > ParamPtrVector;

typedef boost::shared_ptr< param > ParamPtr;
typedef std::vector< ParamPtr, [b]boost::pool_allocator<ParamPtr>[/b] > ParamPtrVector;

class Foo
typedef boost::shared_ptr<Foo> FooPtr;
class MyFunctor{
const FooPtr [b]&[/b]_pFooPtr;
public:
  MyFunctor(const FooPtr &p) : _pFooPtr(p) {}
  bool operator()(const FooPtr &other){
    //bla bla
  } 
};

bool CList::hasKey(const Key &key) const {
    boost::shared_ptr<CList const> pCurList(shared_from_this()); 
    bool res = false;
    do{
        res = _data.find(key) != data.end();
        pCurList = pCurList->getParent();
    } while (!res && pCurList);
   return res;
}

class Key;
class Value;
class CList : public boost::enable_shared_from_this<CList>
{
  std::map<Key, Value> _data;
  std::shared_ptr<CList> _pParentPtr;
public:
    //...
    bool hasKey(const Key &key) const;
    std::shared_ptr<CList> getParent() const{
        return _pParentPtr;
    }