C++:Vector3 类型 "wall"？

Question

假设我有:

class Vector3 {
  float x, y, z;
  ... bunch of cuntions ..
  static operator+(const Vector3&, const Vector3);
};

现在，假设我想要上课:

Position, Velocity, 

与 Vector3 完全一样(基本上，我想要

typedef Vector3 Position;
typedef Vector3 Velocity;

除了，给出:

Position position;
Vector3 vector3;
Velocity velocity;

我想确保以下不能发生:

position + vector3;
vector3 + velocity;
velocity + position;

实现此目标的最佳方法是什么？

Answer 1

我会推荐这样的东西:

template<typename tag>
class Vector3 {
  float x, y, z;
  ... bunch of functions ..
  static operator+(const Vector3&, const Vector3);
};

struct position_tag {};
struct velocity_tag {};
typedef Vector3<position_tag> Position;
typedef Vector3<velocity_tag> Velocity;

请参阅此处以获得更详细的示例:Boost MPL