//Demonstrate the function equal. In this version equal is a friend of the class DayOfYear. 
#include <iostream.h>

class DayOfYear
{
public:
    friend int equal(DayOfYear date1, DayOfYear date2);
    //Precondition: date1 and date2 have values.
    //Returns true if date1 and date2 represent the same date; otherwise returns false.

    DayOfYear(int the_month, int the_day);
    //Precondition: the_month and the_day form a possible date.
    //Initializes the date according to the arguments.

    DayOfYear( );
    //Initializes the date to January first.

    void input( );

    void output( );

    int get_month( );
    //Returns the month, 1 for January, 2 for February, etc.

    int get_day( );
    //Returns the day of the month.
private:
    int month;
    int day;
};

int main( )
{
    DayOfYear today, bach_birthday(3, 21);

    cout << "Enter today's date:\n";
    today.input( );
    cout << "Today's date is ";
    today.output( );

    cout << "J. S. Bach's birthday is ";
    bach_birthday.output( );

    if ( equal(today, bach_birthday))
        cout << "Happy Birthday Johann Sebastian!\n";
    else
        cout << "Happy Unbirthday Johann Sebastian!\n";
    return 0;
}

int equal(DayOfYear date1, DayOfYear date2)
{
    return ( date1.month == date2.month &&
                          date1.day == date2.day );
}

DayOfYear::DayOfYear(int the_month, int the_day)
{
    month = the_month;
    day = the_day;
}
DayOfYear::DayOfYear( )
{
    month = 1;
    day = 1;
}

int DayOfYear::get_month( )
{
    return month;
}

int DayOfYear::get_day( )
{
    return day;
}

//Uses iostream.h:
void DayOfYear::input( )
{
    cout << "Enter the month as a number: ";
    cin >> month;
    cout << "Enter the day of the month: ";
    cin >> day;
}

//Uses iostream.h:
void DayOfYear::output( )
{
    cout << "month = " << month
         << ", day = " << day << endl;
}