package poly;
/**
 * Serves as a factory for manufacturing Polynomial objects.
 * Uses the flyweight pattern to construct the zero polynomial.
 <pre>
 * Copyright 2000, by Dung X. Nguyen, All rights reserved.
 </pre>
 * @author Dung X. Nguyen
 * @since January 01, 2000
 * @dependency poly.APolynomial instantiates
 */
public class PolyFactory
{
	/** @SBGen Variable (,zero polynomial,,64)   */
	public final static APolynomial ZeroPoly = new ConstPoly (0.0);

   /**
   * Creates a constant Polynomial.  Uses the flyweight pattern for the zero polynomial.
   * @return a constant Polynomial.
   */
   public static APolynomial MakeConstPoly (double coef)
   {
      return 0.0 == coef? ZeroPoly: new ConstPoly (coef);
   }

   /**
   * Creates a non-constant Polynomial with a given leading coefficient, a given degree,
   * and a given lower order polynomial.  Checks for legal input parameters.
   * Will ignore zero leading coefficient.
   * @param coef the leading coefficient.
   * @param degree the degree, >= 0.
   * @param lowPoly != null, the lower ordered polynomial with degree < degree.
   * @return a non-constant Polynomial.
   * @exception throws IllegalArgumentException if conditions on degree and lowerPoly are violated.
   */
   public static APolynomial MakePoly (double coef, int degree, APolynomial lowerPoly)
   {
      if (degree <= 0)
      {
         throw new IllegalArgumentException ("Degree must be positive!");
      }
      if (null == lowerPoly)
      {
         throw new IllegalArgumentException ("lowerPoly must be non-null!");
      }
      if (0.0 == coef)
      {
         return lowerPoly;
      }
      if (degree <= lowerPoly.getDegree())
      {
         throw new IllegalArgumentException ("lowPoly is not a lower order term!");
      }
      return new NonConstPoly (coef, degree, lowerPoly);
   }
}