package lrs.visitor;
import lrs.*;

/**
 * Merges the sorted input list into the sorted host list.  In the end, host is sorted.
 * @author Dung X. Nguyen - Copyright 1999 - All rights reserved.
 * @dependency Becomes uses
 */
public class Merger implements IAlgo
{
	/** @SBGen Singleton Variable   */
	public final static Merger Singleton = new Merger ();

	/** @SBGen Constructor   */
	private Merger()
	{
	}
	/**
	 * @param host 
	 * @param input 
	 * @return 
	 */
	public Object nullCase(LRStruct host, Object input)
	{
		return host.execute (Becomes.Singleton, input);
	}

	/**
	 * @param host 
	 * @param input 
	 * @return 
	 */
	public Object nonNullCase(LRStruct host, Object input)
	{
		return ((LRStruct)input).execute (MergeHelper.Singleton, host);
	}

	public static void main(String[] args)
	{
      LRStruct l1 = new LRStruct ();
      l1.insertFront (new Integer (263));
      l1.insertFront (new Integer (15));
      l1.insertFront (new Integer (-9));
      l1.insertFront (new Integer (-72));
      System.out.print ("l1: " + l1);
      System.out.println();
      LRStruct l2 = new LRStruct ();

      /*
      //Testing base case.
      System.out.println ("Merging l1 into l2...");
      l2.execute (Merger.Singleton, l1);
      System.out.println ("l1: " + l1);
      System.out.println ("l2: " + l2);
      */

      l2.insertFront (new Integer (48));
      l2.insertFront (new Integer (0));
      l2.insertFront (new Integer (-2));
      System.out.print ("l2: " + l2);
      System.out.println();
      System.out.println ("Merging l1, l2...");
      l1.execute (Merger.Singleton, l2);
      System.out.println ("l1: " + l1);
      System.out.println ("l2: " + l2);
      System.out.println();
      try
      {
         System.out.println ("Press Enter to quit...");
         System.in.read ();
      }
      catch (Exception e)
      {
      }
   }
}