- friend Point3D operator + (const Point3D& a, const Point3D& b); // p1 + p2
- friend Point3D operator - (const Point3D& a, const Point3D& b); // p1 - p2
- friend Point3D operator * (const Point3D& a, const double d); // p1 * 3.0
- friend Point3D operator * (const double d, const Point3D& a); // 3.0 * p1
- friend Point3D operator / (const Point3D& a, const double d); // p1 / 3.0
- friend bool operator == (const Point3D& a, const Point3D& b); // p1 == p2?
- friend bool operator != (const Point3D& a, const Point3D& b); // p1 != p2?
+ friend bool operator == (const Point3D& a, const Point3D& b); // p1 == p2?
+ friend istream& operator>> ( istream&, Point3D& );
+ friend ostream& operator<< ( ostream&, const Point3D& );