#include<iostream>
using namespace std;
class Complex
{
 private:
     int read; //实部 
     int imag; //虚部   
 public:
 Complex(){read=0;imag=0;}      
 Complex(int r,int i):read(r),imag(i){}//函数的重载 
 Complex Complex_add(Complex &c1); 
 void Complex_input();       
};
Complex Complex::Complex_add(Complex &c) 
{
  Complex sum;    
  sum.read=read+c.read;//??
  sum.imag=imag+c.imag;  
  return sum;     
}
 void Complex::Complex_input()
 {
   cout<<"("<<read<<","<< imag<<"i)"<<endl;        
 }
int main()
{
 Complex c1(3,4),c2(5,-10),c3;
 c3 =c1.Complex_add(c2);
 c3.Complex_input();   
 system("pause");
 return 0;
}

c1,和c2是2个对象，而且也没设定友元函数。为什么通过c1中的函数。然后引用C2也可以完成数据共享呢？