#ifndef _typelist_
#define _typelist_

template<typename H,typename T> struct TypeList {
  typedef H Head;
  typedef T Tail;

};

class  Null_type {};
struct Empty_type {};

template<int N,typename T> struct At {
  typedef typename At<N-1,typename T::Tail>::Result Result;
};

template<typename T> struct At<1,T> {
  typedef typename T::Head Result;
};



template<int N,typename T> struct At2 {
  typedef typename At2<N-1,typename T::Tail>::Result Result;
};

template<typename H,typename T> struct At2<1,TypeList<H,T> > {
  typedef H Result;
};

template<int N> struct At2<N,Null_type> {
  typedef  Empty_type Result;
};


template<typename T,typename TL> struct In {
  enum {yes=In<T,typename TL::Tail>::yes };
};

template<typename T,typename Tail> struct In<T,TypeList<T,Tail> >{
  enum {yes=1};
};

template<typename T> struct In<T,Null_type> {
  enum {yes=0};
};





#endif