/** ADT deque interface

@file DequeInterface.h */

#ifndef _DEQUE_INTERFACE

#define _DEQUE_INTERFACE

template <class ItemType>
class DequeInterface
{
  /** Checks to see if deque is empty

  @pre None.

  @return True if empty, false if not */

  virtual bool empty() const = 0;

  /** Insert a new entry into the front of deque

  @post newEntry is at the

  front of the deque, if the operation is succesful.

  @param newEntry The object to be added as a new entry.

  @return Returns true if addition is successful, otherwise false */

  virtual bool addFront(const ItemType& newEntry) = 0;

  /** Adds a new entry to the back of this deque.

  @post If successful, newEntry is at the

  back of the deque.

  @param newEntry The object to be added as a new entry.

  @return True if the addition is successful or false if not. */

  virtual bool addBack(const ItemType& newEntry) = 0;

  /** Removes the front of this deque.

  @post If the operation was successful, the front of the deque

  has been removed.

  @return True if the removal is successful or false if not. */

  virtual bool removeFront() = 0;

  /** Removes the back of this deque.

  @post If the operation was successful, the front of the deque

  has been removed.

  @return True if the removal is successful or false if not. */

  virtual bool removeBack() = 0;

  /** Returns the front of this deque.

  @pre The deque is not empty.

  @post The front of the deque has been returned, and the

  deque is unchanged.

  @return The front of the deque. */

  virtual ItemType peekFront() const = 0;

  /** Returns the back of this deque.

  @pre The deque is not empty.

  @post The back of the deque has been returned, and the

  deque is unchanged.

  @return The back of the deque. */

  virtual ItemType peekBack() const = 0;
}  // end DequeInterface

#endif