为什么我在这个 C++ 类中的重载 operator+ 不需要实现为 operator-？

Question

friend complex operator +(complex &t1, complex &t2);

complex operator-(complex &t){
    complex tmp(this->a - t.a, this->b - t.b);
    return tmp;
}

I'm learning c++. I don't understand why operator+ don't need to be written as operator-?

Answer 1

Both achieve the same goal. In the first case, the global operator+ function is made friend of this class so it can access private members. The second overloaded operator- is automatically called when '-' is used between two complex objects.