/*     Example of the use of the class RealRoot demonstrating
         the use of the method, RealRoot.bisectNewtonRaphson
         in finding a root of the function, y = a.x^b - 2
*/

import flanagan.roots.*;

// Class to evaluate the function y = a.x^b-2 and its derivative, a.b.x^(b-1)
class Funct implements RealRootDerivFunction{

         private double a = 1.0D;
         private double b = 2.0D;

         public double[ ] function(double x){
                  double[ ] y = new double[2];

                  y[0] = a*Math.pow(x,b) - 2.0D;
                  y[1] = a*b*Math.pow(x,b-1.0D);
                  return y;
         }

         public void setA(double a){
                  this.a = a;
         }

         public void setB(double b){
                  this.b = b;
         }
}

// Class to demonstrate method, RealRoot.bisectNewtonRaphson.
public class RealRootExample{

         public static void main(String[] arg){

                  // Create instance of the class holding the function, y = ax^b - 2, and its derivative
                  Funct func = new Funct();

                  // change value of constant a in the function
                  func.setA(2.0D);

                  // lower bound
                  double lowerBound = 0.0D;
                  // upper bound
                  double upperBound = 2.0D;
                  // required tolerance
                  double tolerance = 1e-6;

                  // Create instance of RealRoot
                  RealRoot  realR = new RealRoot();

                  // Set tolerance
                  realR.setTolerance(tolerance);

                  // call root searching method, bisectNewtonRaphson
                  double root = realR.bisectNewtonRaphson(func, lowerBound, upperBound);

                  // Print root
                  System.out.println("root = "+root);

         }
}