package lrs.visitor;
import lrs.*;

/*
* Removes every other element from host.
*/
public class EveryOther implements IAlgo
{
	public final static EveryOther Singleton = new EveryOther ();

	private EveryOther()
	{
	}

	/**
	 * @param host 
	 * @param input 
	 * @return 
	 */
	public Object nullCase(LRStruct host, Object input)
	{
		return new LRStruct ();
	}

	/**
	 * @param host 
	 * @param input 
	 * @return 
	 */
	public Object nonNullCase(LRStruct host, Object input)
	{
		return host.getRest().execute(EveryOtherHelper.Singleton, host);
	}
   
	public static void main(String[] args)
	{
      LRStruct l1 = new LRStruct ();
      System.out.println ("l1: " + l1);
      System.out.println ("EveryOther l1...");
      LRStruct l2 = (LRStruct)l1.execute(EveryOther.Singleton, null);
      System.out.println ("l1: " + l1);
      System.out.println ("l2: " + l2);
      
      l1.insertFront (new Integer (-9));
      l1.insertFront (new Integer (15));
      l1.insertFront (new Integer (263));
      l1.insertFront (new Integer (-72));
      l1.insertFront (new Integer (0));
      l1.insertFront (new Integer (48));
      System.out.println ("l1: " + l1);
      System.out.println ("EveryOther l1...");
      l2 = (LRStruct)l1.execute(EveryOther.Singleton, null);
      System.out.println ("l1: " + l1);
      System.out.println ("l2: " + l2);
   }
}