/**
 * <<abstract state>>
 * abstract list state
 * @author Dung X. Nguyen - Copyright 1999 - All rights reserved.
 * @since 10/01/99
 * @dependency IAlgo uses
 */
abstract interface IState
{
	/**
	 * @param owner 
	 * @return n
	 */
	abstract QFList getRest(QFList owner);

	/**
	 * @param owner 
	 * @return n
	 */
	abstract Object getFirst(QFList owner);

	/**
	 * @param tail 
	 * @param owner 
	 */
	abstract void setRest(QFList tail, QFList owner);

	/**
	 * @param dat 
	 * @param owner 
	 */
	abstract void setFirst(Object dat, QFList owner);

	/**
	 * @param dat 
	 * @param owner 
	 */
	abstract void insertFront(Object dat, QFList owner);

	/**
	 * @param owner 
	 * @return 
	 */
	abstract Object removeFront(QFList owner);

    abstract Object execute(IAlgo visitor, Object param, QFList owner);
}