package arrayPoly.visitor;

import arrayPoly.*;

/**
* Adds host polynomial to input polynomial.  Returns the resulting sum polynomial.
 <pre>
 * Copyright 2000, by Dung X. Nguyen, All rights reserved.
 </pre>
 * @author Dung X. Nguyen
 * @since 02/16/2000
*/
public class AddAlgo implements IVisitor
{
	public final static AddAlgo Singleton = new AddAlgo ();

	private AddAlgo()
	{
	}
	/**
    * Uses a helper visitor to add a constant to the input APolynomial.
    * The helper visitor can be implemented as an anonymous inner class.
	 * @param poly a Constant polynomial
	 * @param input a APolynomial
	 * @return a APolynomial representing the sum of poly and input.
	 */
	public Object forConst (APolynomial poly, Object input)
	{
      APolynomial p = (APolynomial)input;
      return p.execute (AddConst.Singleton, new Double (poly.getLeadCoef()));
      /*
      //Instead of defining explicitly the helper visitor AddConst, we can uses anonymous
      //inner class to add a constant.  The code is a little harder to read.
      return p.execute (
         new IVisitor ()
         {
	         public Object forConst (APolynomial poly, Object input)
	         {
               return PolyFactory.MakeConstPoly (poly.getLeadCoef() + ((Double)input).doubleValue ());
	         }

	         public Object forNonConst(APolynomial poly, Object input)
	         {
               APolynomial lowerSum = (APolynomial)poly.getLowerPoly().execute (this, input);
                return PolyFactory.MakePoly (poly.getLeadCoef(), poly.getDegree(), lowerSum);
	         }
         }, new Double (poly.getLeadCoef()));
      */
	}

	/**
	 * @param poly a non-constant APolynomial
	 * @param input a APolynomial
	 * @return a APolynomial representing the sum of poly and input.
	 */
	public Object forNonConst(APolynomial poly, Object input)
	{
      APolynomial p = (APolynomial)input;
      double pCoef = p.getLeadCoef();
      int pDegree = p.getDegree();
      double polyCoef = poly.getLeadCoef();
      int polyDegree = poly.getDegree();
      return
         (pDegree < polyDegree)?
            PolyFactory.MakePoly (polyCoef, polyDegree, (APolynomial)poly.getLowerPoly().execute (this, p)):
            (pDegree == polyDegree)?
               PolyFactory.MakePoly (polyCoef + pCoef, polyDegree, (APolynomial)poly.getLowerPoly().execute(this, p.getLowerPoly())):
               PolyFactory.MakePoly (pCoef, pDegree, (APolynomial)poly.execute(this, p.getLowerPoly()));
	}
}