关于C++友元函数的实现讲解

#include <iostream>
#include <cstring>
using namespace std ; 
class Student
{
 private :
 string name ; 
 int age ; 
 char sex ; 
 int score ; 
 public :
 Student(string name , int age , char sex , int score) ;
 //声明友元函数 
 friend void display_information(Student &Stu); 
};
Student::Student(string name , int age , char sex , int score)
{
 this->name = name ; 
 this->age = age ; 
 this->sex = sex ; 
 this->score = score ; 
}
//注意，友元函数不是类Student的成员，但可以访问类中的私有成员变量 
void display_information(Student &Stu)
{
 cout << Stu.name << endl ;
 cout << Stu.age << endl ; 
 cout << Stu.sex << endl ;
 cout << Stu.score << endl ;
}
int main(void)
{
 Student STU1("YYX",24,'N',86);
 display_information(STU1);
 return 0 ;
}