体会友元函数

 【1】

#include "iostream.h"
class B;
class A
{
 int x;
public:
 A(){}
 A(int x){this->x=x;}
 void set(B);
 int get(){return x;}
};
class B
{
 int y;
public:
 B(int y){this->y=y;}
 friend A;
};
void A::set(B b){x=b.y;}
void main()
{
 A a(1);
 B b(2);
 cout<<a.get()<<endl;
 a.set(b);
 cout<<a.get()<<endl;

}

【2】

#include<iostream.h>
#include<string.h>
class Teacher;
class Student
{
private:
 char name[10];
public:
 Student(char n[]){strcpy(name,n);}
 friend void display(Student,Teacher);
};
class Teacher
{
private:
 char name[10];
public:
 Teacher(char n[]){strcpy(name,n);}
 friend void display(Student,Teacher);
};
void display(Student s,Teacher t)
{
 cout<<"the student is:"<<s.name<<endl;
 cout<<"the teacher is:"<<t.name<<endl;
}
void main()
{
 Student s("Li Hui");
 Teacher t("Wang Ping");
 display(s,t);

}