//---------------------------------------------------------------------
// File: stack.h
// Name: Sharon M. Tuttle
// last modified: 3-10-05
//
// Class name: stack
//
// Description: a collection of items such that entries can be
//    inserted and removed at only one end (called the top).
//    This version does NOT have a fixed capacity.
//
//---------------------------------------------------------------------

#ifndef STACK_H
#define STACK_H

#include <cstdlib>	// provides NULL
#include "node.h"
using namespace std;

class stack
{
    public:
        /****************************************************/
        /* TYPEDEFS and MEMBER CONSTANTS                    */
        /****************************************************/

        typedef double value_type;

        /*****************************************************/
        /* CONSTRUCTORS and DESTRUCTORS                      */
        /*****************************************************/

        // postcondition: creates an empty stack instance 
        //
        stack();

        // copy constructor
        //
        stack(const stack& source);

        // destructor
        //
        ~stack( );

        /*************************************************************/
        /* ACCESSORS and other constant member functions (observers) */
        /*************************************************************/

        // postcondition: returns true if stack is empty, and 
        //    returns false otherwise 
        //
        bool is_empty( ) const;

        // precondition: is_empty() == false 
        //
        // postcondition: returns the value of the top item of the 
        //    stack, BUT the stack is unchanged. 
        //
        value_type get_top( ) const;

        // postcondition: returns the number of elements currently 
        //    in the stack
        //
        int get_size( ) const;

        /*****************************************************/
        /* MODIFIERS and other modifying member functions    */
        /*****************************************************/

        // postcondition: a new copy of entry has been pushed 
        //    onto the (top of the) stack 
        //
        void push(const value_type& entry);

        // precondition: is_empty() == false 
        //
        // postcondition: the top item of the stack has been 
        //    removed, and its value is returned
        //
	value_type pop( );

    private:

        /*****************************************************/
        /* DATA FIELDS                                       */
        /*****************************************************/
        node* top;           // pointer to node containing top
                             //    of stack
	int used;	     // how many items are in the stack
};

#endif