package rebelsky.list;

/**
 * Things that indicate positions in a list.
 *
 * @author CSC152 2004F
 */
public interface Position
{
	/**
	 * Get the next position in the list.
	 *
	 * @return n
	 *   the next position.
	 * @pre
	 *   This position is not at the back of the list.
	 * @post
	 *   The previous position of n is this position.
	 * @exception NoSuchPosition
	 *    If this position is at the front of the list.
	 */
	public Position next()
		throws NoSuchPosition;

	/**
	 * Get the previous position in the list.
	 *
	 * @return p
	 *   the previous position.
	 * @pre
	 *   This position is not at the front of the list.
	 * @post
	 *   The next position of p is this position.
	 * @exception NoSuchPosition
	 *    If this position is at the front of the list.
	 */
	public Position prev()
		throws NoSuchPosition;

	/**
	 * Determine if this position is at the back of the list.
	 */
	public boolean atBack();

	/**
	 * Determine if this position is at the back of the list.
	 */
	public boolean atFront();

} // interface Position