/**
 * The PositionalContainer interface specifies a collection of elements of
 * which each element is associated with a position.  The container
 * can be changed.
 *
 * @version     1.4	March 2, 2001
 * @author      Franck van Breugel
 * @see Position
 */
public interface PositionalContainer extends InspectablePositionalContainer
{
    /**
     * Replaces the element at the specified position in this container with 
     * the specified element and returns the replaced element.
     * @param position The position the element of which is to be replaced.
     * @param element The replacement element.
     * @result The replaced element.
     */
    public Object replaceElement(Position position, Object element);

    /**
     * Swaps the elements of the specified positions in this container.
     * @param first The position the element of which is to be swapped.
     * @param second The position the element of which is to be swapped.
     */
    public void swapElements(Position first, Position second);
}