Time Date DateTime的繼承與派生及運算符重載

#include <iostream.h>
class Time{
public:
	Time(){}
	Time(int h,int m,int s)
	{
	 hour=h;
	 minute=m;
	 second=s;
	}
	friend istream & operator>>(istream &,Time &);
	friend ostream & operator<<(ostream &,Time &);
	void operator =(Time &);
	friend bool operator >(Time &t1,Time &t2);
	friend bool operator <(Time &t1,Time &t2);
	friend bool operator ==(Time &t1,Time &t2);
	friend void compare(Time &,Time &);
	void show()
	{
	 cout<<hour<<":"<<minute<<":"<<second<<endl;
	}
	int hour;
	int minute;
	int second;
};
istream & operator>>(istream &input,Time &t1)
{
 input>>t1.hour>>t1.minute>>t1.second;
 return input;
}
ostream & operator<<(ostream &output,Time &t1)
{
 output<<t1.hour<<":"<<t1.minute<<":"<<t1.second;
 return output;
}
void Time::operator =(Time & t1)
{
  hour=t1.hour;
  minute=t1.minute;
  second=t1.second;
}
bool operator >(Time &t1,Time &t2)
{
 if(t1.hour>t2.hour)
	 return true;
 else if(t1.hour==t2.hour&&t1.minute>t2.minute)
	 return true;
 else if(t1.hour==t2.hour&&t1.minute>t2.minute&&t1.second>t2.second)
	 return true;
 else
	 return false;
}
bool operator <(Time &t1,Time &t2)
{
 if(!operator >(t1,t2))
     return true;
 else
	 return false;
}
bool operator ==(Time &t1,Time &t2)
{
 if(t1.hour==t2.hour&&t1.minute==t2.minute&&t1.second==t2.second)
	 return true;
 else
	 return false;
}
void compare(Time &t1,Time &t2)
{
 if(operator>(t1,t2))
	 cout<<"t1>t2";
 if(operator<(t1,t2))
	 cout<<"t1<t2";
 if(operator==(t1,t2))
	 cout<<"t1=t2";
}
class Date{
public:
	Date(){}
	Date(int y,int mo,int d)
	{
	 year=y;
	 month=mo;
	 day=d;
	}
	void get_value()
	{
	 cin>>year>>month>>day;
	}
	void show()
	{
	 cout<<year<<"-"<<month<<"-"<<day<<endl;
	}
protected:
	int year;
	int month;
	int day;
};
class DateTime:public Date,public Time
{
public: 
	DateTime(){}
    DateTime(int y,int mo,int d,int h,int m,int s):Date(y,mo,d),Time(h,m,s){}
	DateTime operator -(DateTime &c2);
	DateTime operator +(Time &t1);
	DateTime operator -(Time &t1);
	void show()
	{
	 cout<<year<<"-"<<month<<"-"<<day<<" "<<hour<<":"<<minute<<":"<<second<<endl;
	}
};
DateTime DateTime::operator -(DateTime &c2)
{
 DateTime c3;
 c3.year=year-c2.year;
 c3.month=month-c2.month;
 c3.day=day-c2.day;
 c3.hour=hour-c2.hour;
 c3.minute=minute-c2.minute;
 c3.second=second-c2.second;
 return c3;
}
DateTime DateTime::operator +(Time &t1)
{
 DateTime c3;
 c3.year=year;
 c3.month=month;
 c3.day=day;
 c3.hour=hour+t1.hour;
 c3.minute=minute+t1.minute;
 c3.second=second+t1.second;
 return c3;
}
DateTime DateTime::operator -(Time &t1)
{
 DateTime c3;
 c3.year=year;
 c3.month=month;
 c3.day=day;
 c3.hour=hour-t1.hour;
 c3.minute=minute-t1.minute;
 c3.second=second-t1.second;
 return c3;
}
int main()
{
 Time t1(12,20,30),t2(10,21,25);
 cout<<"時間t1="<<t1<<endl;
 cout<<"時間t2="<<t2<<endl;
 Time t3,t4;
 cout<<"輸入時間t3:";
 cin>>t3;
 cout<<"時間t3="<<t3<<endl;
 cout<<"時間t1指派給時間t4"<<endl;
 t4=t1;
 cout<<"輸出時間t4=";
 t4.show();
 cout<<"比較時間t1和時間t2:";
 compare(t1,t2);
 Date d1;
 cout<<endl;
 cout<<"輸入日期d1:";
 d1.get_value();
 cout<<"輸出日期d1=";
 d1.show();
 DateTime c1(1996,10,12,12,20,14),c2(1994,4,12,10,1,2);
 DateTime c3,c4,c5;
 cout<<"日期時間c3等于日期時間c1-c2:"<<endl;
 c3=c1-c2;
 cout<<"輸出日期時間c3=";
 c3.show();
 cout<<"日期時間c4等于日期時間c1+時間t1:"<<endl;
 c4=c1+t1;
 cout<<"輸出日期時間c4=";
 c4.show();
 cout<<"日期時間c5等于日期時間c1-時間t1:"<<endl;
 c5=c1-t1;
 cout<<"輸出日期時間c5=";
 c5.show();
 return 0;
}