package polyVisitor;

import arrayPoly.*;

/**
* Evaluates the host polynomial at a double input.  Returns a Double.
 <pre>
 * Copyright 2000, by Dung X. Nguyen, All rights reserved.
 </pre>
 * @author Dung X. Nguyen
 * @since 02/16/2000
*/
public class EvalAlgo implements IVisitor
{
	public final static EvalAlgo Singleton = new EvalAlgo ();

	private EvalAlgo()
	{
	}
	/**
	 * @param poly 
	 * @param input an Double
	 * @return the constant Double value of poly.
	 */
	public Object forConst (APolynomial poly, Object input)
	{
		return new Double (poly.getLeadCoef());
	}

	/**
	 * @param poly 
	 * @param input an Integer
	 * @return the Integer value of poly evaluated at input.
	 */
	public Object forNonConst (APolynomial poly, Object input)
	{
      double x = ((Double)input).intValue ();
      double leadVal = poly.getLeadCoef () * Math.pow (x, poly.getDegree ());
      double lowerVal = ((Double)poly.getLowerPoly().execute(this, input)).doubleValue ();
		return new Double (leadVal + lowerVal);
	}
}