class vector {
public:
 vector(double x = 0, double y = 0, double z = 0);
 vector operator+(vector foo);
 vector operator-(vector foo);
 vector operator*(double foo);
 vector operator=(double foo);
 vector normalized(void);
 double length(void);
 double length_squared(void);
 double x,y,z;
};

vector operator*(double foo, vector bar);