重载+

#include<iostream>
  using namespace std;
  class Complex
   { public:
       Complex() {real=0;imag=0;}
       Complex(double r, double i) {real=r; imag=i; }
Complex operator+(Complex a);
     //friend  Complex operator+(Complex &a, Complex &b);//?不懂为什么声明里也要用&
       void display();
    private:
       double real;
       double imag;
   };
  Complex Complex::operator+(Complex a)//有无&都可以，声明必须和函数头一致


       {return Complex(a.real+real, a.imag+imag);}
 /* Complex operator+(Complex &a, Complex &b)

       {return Complex(a.real+b.real, a.imag+b.imag);}*/
  void Complex::display(){cout<<"("<<real<<","<<imag<<"i)"<<endl;}
  int main()
  {  Complex c1(3,4), c2(5,-10),c3;
     c3=c1+c2;
     cout<<"c1="; c1.display();
     cout<<"c2="; c2.display();
     cout<<"c1+c2="; c3.display();
     return 0;
}