#include <iostream>
#include <cmath>

using namespace std;

/*
 * Shape abstract base class
 */
class Shape {
	protected:
  	  double base;
 	  double height;
	public:
	  Shape():base(0.0), height(0.0) {}
	  Shape(double base, double height): base(base), height(height) {}
	  void setBase(double base) {
	    this->base = base;
	  }
	  void setHeight(double height) {
	    this->height = height;
	  }

	  double getBase() {
		  return base;
	  }
	  double getHeight() {
		  return height;
	  }

	  virtual double area() = 0;   //abstract or pure virtual function
};
		

/*
 * Derived class (non abstract) with a virtual final function
 */
class Triangle: public Shape {
  public:
	  Triangle(): Shape() {}
	  Triangle(double base, double height): Shape(base, height) {}
	  
	  //final can be used only to non-static virtual function
	  virtual double area() override final{
	    cout<<"Triangle area..."<<endl;
	    return 0.5*base*height;
	  }
};



/*
 * Derived class not able to override a final function of its base class
 */
class RightTriangle: public Triangle {
public:
  RightTriangle(): Triangle() {}
  RightTriangle(double base, double height): Triangle(base, height) {}
  //virtual final method cannot be overriden
  // double area() {
  //   cout<<"RightTriangle area...."<<endl;
  //   return 0.5*base*height;
  // }
};



/*
 * A final class that cannot be used as a base class to derive another
 * new class.
 */
class Utility final {
public:
  double square(double number) {
    return number*number;
  }
};


//It is not allowed to define a subclass of
//final class
// class SubUtility: public Utility {
// public:
//   double squareRoot(double number) {
//     return sqrt(number);
//   }
// };



int main() {

  Triangle triangle(3,4);
  cout<<triangle.area()<<endl;
  RightTriangle rightTriangle(3,4);
  cout<<rightTriangle.area()<<endl;

  Triangle& refTriangle1 = triangle;
  cout<<refTriangle1.area()<<endl;
  Triangle& refTriangle2 = rightTriangle;
  cout<<refTriangle2.area()<<endl;

  double number = 4.0;
  Utility util;
  cout<<"The square of: "<<number<<" is: "<<util.square(number)<<endl;

  // SubUtility sUtil;
  // cout<<"The square root of: "<<number<<" is: "<<sUtil.squareRoot(number)<<endl;
}