Question

关于C++友元函数重载问题，下面是我写的程序，可在VC6.0显示错误。

#include<iostream>
using namespace std;
class complex
{
protected:
double real;
double image;
public:
complex(double r=0,double i=0):real(r),image(i){}
void set(double r,double i){real=r; image=i;}
double Getreal() { return real; }
double Getimage(){ return image; }
friend istream &operator >>(istream &in, complex &z);
friend ostream &operator <<(ostream &out,complex &z);

};
istream &operator>>(istream &in, complex &z)
{

cout<<"输入实部："<<endl;
in>>z.real;
cout<<"输入虚部："<<endl;
in>>z.image;

return in;
}

ostream &operator<<(ostream &out,complex &z)
{

out<<z.real<<"+"<<z.image<<"i"<<endl;

return out;
}

int main()
{
complex t1;
complex t2;

cin>>t1;
cin>>t2;
cout<<t1;
cout<<t2;

return 0;
}
/* error C2248: 'real' : cannot access protected member declared in class 'complex'
C:\Documents and Settings\Owner\My Documents\Text1.cpp(6) : see declaration of 'real'
C:\Documents and Settings\Owner\My Documents\Text1.cpp(23) : error C2248: 'image' : cannot access protected member declared in class 'complex'
C:\Documents and Settings\Owner\My Documents\Text1.cpp(7) : see declaration of 'image'
C:\Documents and Settings\Owner\My Documents\Text1.cpp(31) : error C2248: 'real' : cannot access protected member declared in class 'complex'
C:\Documents and Settings\Owner\My Documents\Text1.cpp(6) : see declaration of 'real'
C:\Documents and Settings\Owner\My Documents\Text1.cpp(31) : error C2248: 'image' : cannot access protected member declared in class 'complex'
C:\Documents and Settings\Owner\My Documents\Text1.cpp(7) : see declaration of 'image'
C:\Documents and Settings\Owner\My Documents\Text1.cpp(41) : error C2593: 'operator >>' is ambiguous
C:\Documents and Settings\Owner\My Documents\Text1.cpp(42) : error C2593: 'operator >>' is ambiguous
C:\Documents and Settings\Owner\My Documents\Text1.cpp(43) : error C2593: 'operator <<' is ambiguous
C:\Documents and Settings\Owner\My Documents\Text1.cpp(44) : error C2593: 'operator <<' is ambiguous
Error executing cl.exe. */
//求高手帮我看看，做很久了，不知道为什么？
估计是我的VC编译器出问题！

Answer 1

#include <iostream>
using namespace std;

class complex {
protected:
double real;
double image;
public:
complex(double r=0,double i=0):real(r),image(i){}
void set(double r,double i){real=r; image=i;}
double Getreal() {return real;}
double Getimage() {return image;}
friend istream &operator>>(istream &in, complex &z);
friend ostream &operator<<(ostream &out,complex &z);
};

istream &operator>>(istream &in, complex &z) {
cout<<"输入实部："<<endl;
in>>z.real;
cout<<"输入虚部："<<endl;
in>>z.image;
return in;
}

ostream &operator<<(ostream &out,complex &z) {
out<<z.real<<"+"<<z.image<<"i"<<endl;
return out;
}

int main()
{
complex t1;
complex t2;
cin>>t1;
cin>>t2;
cout<<t1;
cout<<t2;
return 0;
}

试一下，protect的问题不知道是不是VC的问题，VS下运行没有问题，你的operator定义友元函数时不要在操作符前加空格

我这个程序也不能运行吗？应该不会吧。。。

Answer 2

protected:
友元不能访问保护 成员
改为private

Answer 3

重载运算符有岐义。
in>>应该是cin>>吧。

Answer 4

什么的