[求助]给类加个友元输出操作符，怎么编译说不能访问私有成员？

以下是引用aipb2007在2007-5-4 15:01:10的发言：
https://bbs.bc-cn.net/viewthread.php?tid=133743&extra=&page=10#112525


看看这帖子

怎么我该掉了还是不行?

以下是引用aipb2007在2007-5-4 17:06:55的发言：
开始么看你代码，错误还真多！

[CODE]#include <iostream>
#include <string> //你用了string
class student
{
public:
student(){}
student(const std::string &name,char c,unsigned int age):stdname(name),sex(c),stdage(age){}//内置类型最
//好不用引用，年龄该unsigned int吧
friend std::ostream &operator<<(std::ostream &,const student &);
~student(){}
private:
std::string stdname;
char sex;
unsigned int stdage;//还有这里
};
std::ostream &operator<<(std::ostream &os,const student &std)//最严重，你重载的是<<怎么变成>>，是ostream
//不是istream
{
os<<std.stdname<<' '<<std.sex<<' '<<std.stdage;
return os;
}
int main()
{
student st("zhangjiao",'m',21);
std::cout<<st<<std::endl;
return 0;
}[/CODE]

真是太感谢你啦！
那这种方式里面要用字符串岂不是非要要C风格的？

用iostream不能用friend访问private成员，要访问就要iostream.h;用string，加上std::，又说不能访问私有的，如下：
#include <iostream.h>
#include <string>
class student
{
public:
student(){}
student(const std::string &name,char c,unsigned int age):stdname(name),sex(c),stdage(age) {}
friend ostream &operator<<(ostream &,const student &);
~student(){}
private:
std::string stdname;
char sex;
unsigned int stdage;//还有这里
};
ostream &operator<<(ostream &os,const student &std)//最严重，你重载的是<<怎么变成>>，是ostream
//不是istream
{
os<<std.stdname<<' '<<std.sex<<' '<<std.stdage;
return os;
}
int main()
{
student st("zhangjiao",'m',21);
cout<<st<<endl;
return 0;
}
compiling...
4.cpp
D:\VC\MSDev98\MyProjects\4\4.cpp(19) : error C2679: binary '<<' : no operator defined which takes a right-hand operand of type 'const class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >' (or there is no acceptable
conversion)
Error executing cl.exe.

4.obj - 1 error(s), 0 warning(s)

谢谢啦哈！