/**
* Represents the constant polynomial type.
* @author Dung X. Nguyen
*/
class ConstPoly extends APolynomial
{
   /**
	 * @param coef  the constant coefficient for this ConstPoly.
	 */
	public 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!");
	}

	/**
	 * If parameter p is a constant polynomial then return a ConstPoly whose coefficient
   * is the sum of the coefficients of this ConstPoly and p.
   * Otherwise asks p to add this APolynomial to itself.
	 */
	public APolynomial add(APolynomial p)
	{
     return
        0 == p.getDegree()?
           new ConstPoly (_coef + p.getLeadCoef()):
           p.add (this);
           /* Software Engineering Issue: The previous line of code can be replaced by
            * new NonConstPoly (p.getLeadCoef(), p.getDegree(), p.getLowerPoly().add (this));
            * Perhaps this is more efficient, but it introduces a loose coupling between
            * ConstPoly and NonConstPoly: ConstPoly must know how to call the constructor
            * for NonConstPoly.
           */
	}

	/**
	 * Returns the coefficient of this ConstPoly.
	 */
	public double eval(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.
   */
   String toString4LowerPoly ()
   {
      return (0 == _coef)? "": " + " + Double.toString(_coef);
   }
}