未知类型名称向量

Question

Here's point.h

#ifndef POINT_H_
#define POINT_H_
#include "/Users/Verdonckt/Documents/3dlaboNogMaarEens/3dlaboNogMaarEens/src/util/Vector.h"
class Point {

public:

    double x;
    double y;
    double z;

    Point(double x=0, double y=0, double z=0): x(x), y(y), z(z){ }

    void set(double x, double y, double z);
    friend Vector operator-(const Point& left, const Point& right);
};

#endif /* POINT_H_ */

This files gives an error on line:

friend Vector operator-(const Point& left, const Point& right);

Saying unknown type name: I think the include works since it doesn't give an error an it would if I change it to a non existing file.

here's Vector.h:

#ifndef VECTOR_H_
#define VECTOR_H_

#include "Point.h"
class Vector {

public:

double x, y, z;

Vector(double x=0, double y=0, double z=0):x(x), y(y), z(z){ }

Vector(const Point & from, const Point & to);

Vector(const Point& p):x(p.x),y(p.y), z(p.z){ }
    double getX(){return x;}
    double getY(){return y;}
    double getZ(){return z;}

    friend Vector operator*(const Vector & v, double a);

    friend Vector operator*(double a, const Vector & v);

    friend Point operator+(const Point & p, const Vector & v);

    friend Point operator+(const Vector & v, const Point & p);

    friend Vector operator+(const Vector & v1, const Vector & v2);
    friend Vector operator-(const Vector& v1, const Vector& v2);

    double dot(const Vector & v);

    Vector cross(const Vector & v);
    double length();
    void normalize();

};

#endif /* VECTOR_H_ */

Once again saying on lines:

friend Point operator+(const Point & p, const Vector & v);
friend Point operator+(const Vector & v, const Point & p);
Vector(const Point & from, const Point & to);
Vector(const Point& p):x(p.x),y(p.y), z(p.z){ }

Unknown type name 'Point'

Why is this and how do I resolve this?

Answer 1

You have a circular dependency - Vector.h and Point.h each try to include the other. The include guards will prevent serious problems, but you'll end up with one of the classes defined before the other, and the name of the second will not be available within the first.

Luckily, Point doesn't need a full definition of Vector - a forward declaration will do.

class Vector;
class Point {
    // ...

    // No problem using `Vector` to declare a return type here
    friend Vector operator-(const Point& left, const Point& right);
};