SOURCE FILE: deque.h

// ********************************************************
// Header file deque.h for the ADT deque.
// Pointer-based implementation.
// ********************************************************

typedef double dequeItemType ;

// The deque is implemented as a circular doubly linked list
// with one external pointer to the back of the deque.

struct dequeNode;  

typedef dequeNode* ptrType;

class dequeClass
{
public:
// constructors and destructor:
   dequeClass();                     // default constructor
   ~dequeClass();                    // destructor

// deque operations:

   int Length() const;
   // Determines the length of a deque.
   // Precondition: None.
   // Postcondition: Returns the number of items
   // that are currently in the deque.

   bool IsEmpty() const;
   // Determines whether a deque is empty.
   // Precondition: None.
   // Postcondition: Returns true if the deque is empty;
   // otherwise returns false.

   void AddInFront(dequeItemType NewItem, bool& Success);
   // Adds an item to the front of a deque.
   // Precondition: NewItem is the item to be added.
   // Postcondition: If insertion was successful, NewItem
   // is at the front of the deque and Success is true; 
   // otherwise Success is false.

   void AddInRear(dequeItemType NewItem, bool& Success);
   // Adds an item to the rear of a deque.
   // Precondition: NewItem is the item to be added.
   // Postcondition: If insertion was successful, NewItem
   // is at the rear of the deque and Success is true; 
   // otherwise Success is false.

   void TakeOutFront(dequeItemType& DequeFront, bool& Success);
   // Retrieves and removes the front of a deque.
   // Precondition: None.
   // Postcondition: If the deque was not empty, DequeFront
   // contains the item that was at the front of the Deque,
   // the item is removed, and Success is true. However, if the
   // deque was empty, deletion is impossible, DequeFront is 
   // unchanged, and Success is false.

   void TakeOutRear(dequeItemType& DequeRear, bool& Success);
   // Retrieves and removes the rear of a deque.
   // Precondition: None.
   // Postcondition: If the deque was not empty, DequeRear
   // contains the item that was at the rear of the Deque,
   // the item is removed, and Success is true. However, if the
   // deque was empty, deletion is impossible, DequeRear is 
   // unchanged, and Success is false.

   void Print() const;
   // Prints the contents of the Deque in front-to-back order.
   // (Prints to standard output.)
   // Does nothing if the Deque is empty.
   // Precondition: None
   // Postcondition: Deque is unchanged.

private:
   ptrType BackPtr;
   int Size ;
};  // end class
// End of header file.