/************************************************************
** Maysa Peterson       SE507       Formal Specifications		     	     **
** Arila Attanosova                     CS AP Specifications for C+ 		                 **
**                                                    March6,  1996 			     	     **
************************************************************/


/************************************************************
** APCS stack class								     **
**											     **
** Specifications for queue functions	 				                 **
**											     **
** Any violation of a function's precondition will result in an error 	     **
** message followed by a call to abort.						     **
************************************************************/

template <class itemType>

class stack
{
	public:

/************************************************************
** constructors/destructors - for initialing and  finalizing data structure of**
** type queue									      **
************************************************************/	
	stack( );     		// construct empty queue
	stack(stack s);  	// copy constructor 
	~stack( );		// destructor - queue is destroyed


/************************************************************
** assignment -  normal assignment via copying is been performed below  **
************************************************************/

	stack operator = (stack righthandside);

/************************************************************
** accessors - "const" indicates that the original queue is not altered 	      **
************************************************************/

		itemType  top( )      const;               // return top element (NO pop)

/************************************************************
**		given stack is [a1, a2, ..., an] with n >= 1				      **
**		function returns an						      **
************************************************************/

		bool  isEmpty( )  const;                 // return true if empty, else false

/************************************************************
**		function returns true if queue is empty, false otherwise	      **
************************************************************/

		int   length( )   const;                // return stack size in length 

/************************************************************
**		given queue is [a1, a2, ..., an] with n >= 0			      **
**		function  returns n						      **
************************************************************/


/*  modifying procedures defined below:					      */


		push(itemType  item );		// push item onto top of stack

/************************************************************
**		precondition: stack is [a1, a2...an] with  n >= 0			      **
**		postcondition: stack is [a1, a2, ... an, item]			      **
************************************************************/

		pop( );				// pop top element

/************************************************************
**		precondition: stack is [a1, a2, ... an] with n >= 1		      **
**		postcondition: stack is [a1, a2, ... a(n-1)]			      **
************************************************************/

		pop( itemType  item );	// combines pop and top

/************************************************************
**		precondition: stack is [a1,a2,...an] with n >= 1			      **
**		postcondition: stack is [a1,a2,...a(n-1)] and item == en	      **
************************************************************/

     		makeEmpty( );		// make stack empty (no elements)

/************************************************************
**		precondition: stack is [a1,a2,...an] with n >= 0			      **
**		postcondition:  stack is empty 					      **
************************************************************/
	
	private:

/*        implementation will be supplied later					       */
};