package scheme2.visitor;

import scheme2.AListFW;
import scheme2.IListAlgo;

public class Sum implements IListAlgo
{
	/** @SBGen Singleton Variable   */
	public final static Sum Singleton = new Sum ();

	/** @SBGen Constructor   */
	private Sum()
	{
	}

	/**
	 * @param host 
	 * @param input not used.
	 * @return 
	 */
	public Object forEmpty(AListFW host, Object input)
	{
		return new Integer (0);  // Empty Range Axiom!
	}

	/**
	 * @param host 
	 * @param input not used 
	 * @return 
	 */
	public Object forNonEmpty(AListFW host, Object input)
	{
      Integer restSum = (Integer)host.getRest ().execute (this, null);
		return new Integer (((Integer)host.getFirst ()).intValue () + restSum.intValue ());
	}
}