/* 
 *  File: stack.h
 *        A template class definition for a Stack ADT 
 *        using a linked-list representation
 *
 *  From Dr. Mateen Rizki
 *
 *  Modified: spc
 *
 * DESCRIPTION: stack<Stack_entry> is a stack of objects
 *   The template parameter Stack_entry is the type of items contained.
 *
 * OPERATIONS:
 *   stack()
 *     Post: Initializes an empty stack.
 *
 *   push(const Stack_entry& item)
 *     Pre:  none
 *     Post: copy of item has been pushed onto the stack
 *
 *   pop()
 *     Pre:  top_node != NULL
 *     Post: top item of the stack has been removed
 *
 *   Stack_entry top()
 *     Precondition: top_node != NULL
 *     Postcondition: top item of the stack is returned and stack unchanged;
 *      throws exception if stack is empty
 *
 *   empty()
 *     Postcondition: Returns true if stack empty, false otherwise
 *
 * SEMANTICS:
 *   This class has reference semantics.
 */

#ifndef _STACK
#define _STACK

#include <string>
using namespace std;

template <class Stack_entry>
class stack {
public:

	class node {
	public:
		Stack_entry data;
		node *next;
	};

   stack();
   bool empty() const;
   void pop();
   Stack_entry top() const;
   void push(const Stack_entry&);

private:
	node *top_node;
};

#endif