c++之学习程序complex_3

处理一个复数与一个double数相加的运算，结果存放在一个double型的变量中，并输出该变量的值，再以复数的形式输出此值。

#include<iostream.h>
class complex
{
public:
 complex(){real=0;imag=0;}
 complex(double r){real=r;imag=0;}
 complex(double r,double i){real=r;imag=i;}
 operator double(){return real;}//重载类型转换运算符
 friend ostream& operator<<(ostream &,complex &);
private:
 double real;
 double imag;
};
ostream& operator <<(ostream &out,complex &a)
{
 out<<"("<<a.real<<","<<a.imag<<"i)"<<endl;
 return out;
}
int main()
{
 complex a(3,5),b;
 double c,d;
 cout<<"the complex is :"<<endl;
 cout<<a;
 cout<<"input a double number:";
 cin>>d;
 c=2.5+a;
 cout<<"the double number"<<d<<"+the complex"<<a<<"is:";
 cout<<c<<endl;
 return 0;
}