//file stack.h declares the class Stack and Element.
#ifndef STACK_H
#define STACK_H

#include <stdexcept>
using namespace std;
class Element;  //details in stack.cpp

class Stack{
 public:
   Stack():first(0){}
   ~Stack();
   void push(int d);
   int top() throw(length_error);
   void pop() throw(length_error);
   bool empty();
   void debug();//nonstandard!
 private:
  Element *first;
  Stack(const Stack&){}// Blocks the default stack copy operation
  Stack& operator=(const Stack&){return *this;}//null assignment

};



#endif