package list;

/**
 * Copyright 2000 - Dung X. Nguyen - All rights reserved.
 * @dependency scheme2.IListAlgo 
 */
public abstract class AList
{
    /**
    * Returns the first element in this AList, if any.
    * 
    * @exception IllegalArgumentException whenever this AList is empty.
    */
    public abstract Object getFirst();

    /**
    * Returns the tail ("rest") of this AList, if any.
    * 
    * @exception IllegalArgumentException whenever this AList is empty.
    */
    public abstract AList  getRest();

    /**
    * Serves as interface for the different functions.
    */
    public abstract Object execute(IListAlgo algo, Object input);
}