【运算符重载】基本概念

把运算符的操作数转换成运算符函数的参数

返回值类型 operator 运算符（形参表） { ... }

class Complex {
public:
  double real, image;
  Complex(double r = 0.0, double i = 0.0):real(r),image(i) {}
  Complex operator+(const Complex & a, const Complex & b) {
      return Complex(a.real + b.real, a.image + b.image); // 返回一个临时对象
  }
  Complex Comlpex::operator-(const Complex & c) {
      return Complex(real - c.real, imgae - c.image);
  }
}

重载为成员函数时，参数个数是运算符的目数减一

main() {
  Complex a(4,4), b(1,1), c;
  c = a + b; // 等价于 c = operator+(a,b)
  cout << (a-b).real << endl; // 等价于 a.operator-(b)
}