//或许，友元是VC++6.0心里永远的痛，对于这个BUG我一直很介意。
//注：这个程序在VC++6.0里是行不通的，在VS2008里是可以的。
#include <iostream>

#include <string>

using namespace std;

class Student; //提前引用声明

//声明Teacher类

class Teacher {

public:

    Teacher(){}

    Teacher(int i,string s,char c,int t=):num(i),name(s),sex(c),theachYears(t){}

    Teacher(Student);

    friend ostream& operator<<(ostream& out,Teacher& te);

private:

    int num;

    string name;

    char sex;//F/M

    int theachYears;

};

//声明Student类

class Student {

public:

    Student(){}

    Student(int i,string s,char c,int g=):num(i),name(s),sex(c),grade(g){}

    friend Teacher::Teacher(Student);

    friend ostream& operator<<(ostream& out,Student& st);

private:

    int num;

    string name;

    char sex;//F/M

    int grade;

};

//注意：根据惯例，我们喜欢在类的声明前直接写成员函数的实现；

//但是，该构造函数的实现不能写在Student类声明之前，
//因为它使用了Student类的成员，提前引用声明在这里将不起作用

Teacher::Teacher(Student st)

    {

    num=st.num;

    name=st.name;

    sex=st.sex;

    theachYears=;

    }

//重载Teacher类的<<  
// 注意：该构造函数的实现不能写在Student类声明之前，原因同上

ostream& operator<<(ostream& out,Teacher& te)

{

    out<<"num="<<te.num<<","<<"name="<<te.name<<","<<"sex="<<te.sex<<","<<"theachYears="<<te.theachYears<<endl;

    return out;

}

//重载Student类的<<

ostream& operator<<(ostream& out,Student& st)

{

    out<<"num="<<st.num<<","<<"name="<<st.name<<","<<"sex="<<st.sex<<","<<"grade="<<st.grade<<endl;

    return out;

}

int main()

{

    Student s(,"xiaoer",'F',);

    cout<<s;

    Teacher t=Teacher(s);

    cout<<t;

    return ;

}