class mylinkage
{
protected:
   mylinkage * prev;
   mylinkage * next;

public:
   void set_prev(mylinkage* L);
   void set_next(mylinkage* L);
   mylinkage * succ();
   mylinkage * pred();
   mylinkage();

};

class Collection;

class mylink : public mylinkage
{
private:

public:

  void into(Collection * Q);
  void append(Collection * Q);
  mylink* out();

};

class Collection : public mylinkage
{
private:

public:

   mylink* out();
   mylink * first();
   mylink * last();
   int empty();
   void out_of(mylink* ob);
   void add_before(mylinkage*,mylink*);
   void append(mylink*);
   Collection();

};