友元成员函数的简单应用

#include <iostream>

/* run this program using the console pauser or add your own getch, system("pause") or input loop */
using namespace std;
class Date;
class Time
{
    public:
        Time(int,int,int);
        void display(Date &);
    private:
        int hour;
        int minute;
        int sec;
};

class Date
{
    public:
        Date(int,int,int);
        friend void Time::display(Date &);
    private:
        int month;
        int day;
        int year;
};

Time::Time(int h,int m,int s)
{
    hour=h;
    minute=m;
    sec=s;
}

void Time::display(Date &d)
{
    cout<<d.month<<"/"<<d.day<<"/"<<d.year<<endl;
    cout<<hour<<":"<<minute<<":"<<sec<<endl;
}

Date::Date(int m,int d,int y)
{
    month=m;
    day=d;
    year=y;
}

int main(int argc, char** argv) {
    Time t1(10,13,56);
    Date d1(12,25,2004);
    t1.display(d1);    
    return 0;
}