多态性3

#include<iostream>
using namespace std;
class Complex{
public:
Complex(double r=0.0,double i=0.0):real(r),imag(i) {}
friend Complex operator+(const Complex &c1,const Complex &c2);
friend Complex operator-(const Complex &c1,const Complex &c2);
friend ostream & operator<<(ostream &out,const Complex &c);
private:
double real;
double imag;
};
Complex operator+(const Complex &c1,const Complex &c2){
return Complex(c1.real+c2.real,c1.imag+c2.imag);
}
Complex operator-(const Complex &c1,const Complex &c2){
return Complex(c1.real-c2.real,c1.imag-c2.imag);
}
ostream & operator<<(ostream &out,const Complex &c){
cout<<"("<<c.real<<","<<c.imag<<")";
return out;
}
int main()
{
Complex c1(5,4),c2(2,10),c3;
cout<<"c1="<<c1<<endl;
cout<<"c2="<<c2<<endl;
c3=c2-c1;
cout<<"c3=c1-c2="<<c3<<endl;
c3=c1+c2;
cout<<"c3=c2+c1"<<c3<<endl;
return 0;
}