package poly;
/**
* Represents the constant polynomial type.
* @author Dung X. Nguyen
*/
class ConstPoly extends APolynomial
{
   /**
	 * @param coef  the constant coefficient for this ConstPoly.
	 */
	ConstPoly(double coef)
	{
      _coef = coef;
	}

	public int getDegree()
	{
		 return 0;
	}

	/**
	 * Throws NoSuchElementException.
	 */
	public APolynomial getLowerPoly()
	{
		 throw new java.util.NoSuchElementException ("Constant polynomial has no lower order term!");
	}

	/**
   * Passes _coef to p for p to add.
   */
	public APolynomial add(APolynomial p)
	{
      return p.addConst (_coef);
	}

	/**
	 * Returns the coefficient of this ConstPoly.
	 */
	public double eval(double x)
	{
		 return _coef;
	}

	/**
	 * Returns the coefficient of this ConstPoly.
	 */
	public double evalHorner (double x)
   {
      return _coef;
   }

   /**
   * Returns the String representation of the coefficient of this ConstPoly.
   */
   public String toString ()
   {
      return Double.toString(_coef);
   }

   /**
   * Called by an APolynomial that contains this ConstPoly as its lower order polynomial.
   * Returns the empty String if this ConstPoly is the zero polynomial, otherwise
   * returns " + " followed by the String representation of this ConstPoly's coefficient.
   */
   protected String toString4LowerPoly ()
   {
      return (0 == _coef)? "": " + " + Double.toString(_coef);
   }

	/**
   * Returns a ConstPoly whose coefficient is the sum of _coef with the double parameter.
   */
	protected APolynomial addConst (double c)
   {
      return PolyFactory.MakeConstPoly (_coef + c);
   }

   /**
   * Terminates evalHornerHelp recursive call.  Raises x to the power of the enclosing
   * higher order polynomial.  Multiply it by the accumulated computed value.  Add the
   * result to _coef and returns the sum.
   */
	protected double evalHornerHelp (double x, double acc, int preDegree)
   {
      return acc * Math.pow (x, preDegree) + _coef;
   }

   /**
   * Divides _coef into the dividend APolynomial.
   * @throw IllegalArgumentException if _coef is zero.
   */
   protected QRPair divmodInto(APolynomial dividend)
   {
      if (0.0 == _coef)
      {
         throw new IllegalArgumentException ("Divide by 0!");
      }
      return new QRPair (dividend.multMonomial (1.0 / _coef, 0), PolyFactory.ZeroPoly);
   }

   /**
   * Returns a ConstPoly whose coefficient is the product of this _coef and the input coef,
   * if the input degree is zero, else returns APolynomial with coefficient coef * _coef,
   * order degree, and the zero polynomial as the lower order polynomial. 
   */
   protected APolynomial multMonomial (double coef, int degree)
   {
      return 0 == degree?
                PolyFactory.MakeConstPoly (coef * _coef):
                PolyFactory.MakePoly(coef * _coef, degree, PolyFactory.ZeroPoly);
   }
}