// Class Point definition - in a header filer. Declaration of operator<< outside the class.  
// Class design (class definition) separated from class implementation (member definition).

class Point {
private: 
  double x, y;

public:
  Point(double, double);
  Point();
  double getx () const;
  double gety () const;
  void move(double, double);
  double distance_to(Point) const;
};

std::ostream& operator<<(std::ostream&, const Point&);