Thread: Inheritance problem

Originally Posted by patricio2626

Yeah, it's specified as inheritance in the book, so that's the example I'm trying to implement. So, you're saying that I should instantiate an object of the base class in the inherited class, and use that object's variables for instantiation of a derived class object.

Not exactly, I was just thinking more along the line of "a Circle has-a (center) Point", rather than "a Circle is-a Point".

If it's an exercise in inheritance, that wouldn't be much different.

Code:

class Circle : public Point
{
   double radius;
public:
   Circle(double radius_, double x_ = 0, double y_ = 0)
   : Point(x_, y_), radius(radius_)
   {
   }
   double area()
   {
      return PI * radius * radius;
   }
};

What I think was a key issue with your earlier attempts was the distance function.

Code:

class Point
{
   double x, y;
public:
   Point(double x_ = 0, double y_ = 0) : x(x_), y(y_)
   {
   }
   friend double distance(const Point& pt1, const Point& pt2)
   {
      double a = pt2.x - pt1.x, b = pt2.y - pt1.y;
      return std::sqrt(a * a + b * b);
   }
};