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Page 873
    RelationType ComparedTo( /* in */ DateType otherDate ) const;
        // Postcondition:
        //     Function value == BEFORE, if this date is
        //                               before otherDate
        //                    == SAME, if this date equals otherDate
        //                    == AFTER, if this date is
        //                              after otherDate

    void Increment();
        // Postcondition;
        //     Date has been advanced by one day

    DateType();
        // Postcondition:
        //     New DateType object is constructed with a
        //     month, day, and year of 1, 1, and 1583
private:
    int mo;
    int day;
    int yr;
};
Implementation of the ADT: We have already chosen a concrete data representation for a date, shown in the specification file as the int variables mo, day, and yr. Now we must implement each class member function, placing the function definitions into a C++ implementation file named, say, datetype.cpp. As we implement the member functions, we also discuss testing strategies that can help to convince us that the implementations are correct.
The class constructor, Set, Month, Day, and Year functions: The implementations of these functions are so straightforward that no discussion is needed.
The class constructor DateType()
Set mo = 1
Set day = 1
Set yr = 1583

 
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