/**
 * The InspectableBinaryTree interface specifies a binary tree the elements of which
 * are associated with positions.
 *
 * @version     1.3    March 4, 2001
 * @author      Franck van Breugel
 * @see Position
 */
public interface InspectableBinaryTree extends InspectableTree 
{
    /**
     * Returns the left child of the specified position.
     * Throws an InvalidPositionException if the specified position does not have 
     * a left child.
     * @param position The position of which the left child is to be returned.
     * @return The left child of the specified position.
     * @exception InvalidPositionException if the specified position does not have 
     * a left child.
     */
    public Position leftChild(Position position) throws InvalidPositionException;

    /**
     * Returns the right child of the specified position.
     * Throws a InvalidPositionException if the specified position does not have a
     * right child.
     * @param position The position of which the right child is to be returned.
     * @return The right child of the specified position.
     * @exception InvalidPositionException if the specified position does not have a 
     * right child.
     */
    public Position rightChild(Position position) throws InvalidPositionException;

    /**
     * Returns the sibling of the specified position.
     * Throws a InvalidPositionException if the specified position does not have
     * a sibling.
     * @param position The position of which the sibling is to be returned.
     * @exception InvalidPositionException if the specified position does not
     * have a sibling.
     */
    public Position sibling(Position position) throws InvalidPositionException;
}