class Simpson extends Program {
  void run() {
    print  (" area sin(x)= " + new FunSin().area(0.0, PI/2, 100));
    println(" area sin(x)= " + new FunSin().area(0.0, PI/2, 1000));
    print  (" area exp(x)= " + new FunExp().area(0.0, 1.0, 100));
    println(" area exp(x)= " + new FunExp().area(0.0, 1.0, 1000));
    print  (" area x^3= " + new FunXk(3).area(0.0, 1.0, 100));
    println(" area x^3= " + new FunXk(3).area(0.0, 1.0, 1000));
  }
}

class Funcion extends Program {
  double eval(double x) {
    return 0.0;
  }
  double area(double a, double b, int n) { // por metodo de Simpson
    double delta= (b-a)/n;
    double sum= eval(a)+eval(b);     // f(a) + f(b)
    double x= a+delta;
    sum+= 4*eval(x);                 // +4*f(a+delta)
    x+= delta;
    for(int i=2; i<n; i+=2) {        // +2*f(a+i*delta)+4*f(a+(i+1)*delta)
      sum+= 2*eval(x);               // i=2 ... n-2
      x+= delta;
      sum+= 4*eval(x);
      x+= delta;
    }
    return delta*sum/3;
  }
}

class FunSin extends Funcion {
  double eval(double x) {
    return sin(x);
  }
  // area se hereda
}
class FunExp extends Funcion {
  double eval(double x) {
    return exp(x);
  }
  // area se hereda
}
class FunXk extends Funcion {
  int k;
  FunXk(int k) {
    this.k= k;
  }
  double eval(double x) {
    return pow(x, k);
  }
  // area se hereda
}