date.h

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// File Name: Date.h
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#ifndef DATE_H
#define DATE_H

class Date
{
protected:
    static const int dys[];
    long int ndays; // days inclusive since Jan 1,1 (1/1/1==1)

public:
    // Default and initializing constructor.
    Date(int mo = 0, int da = 0, int yr = 0)
        { SetDate(mo, da, yr); }

    // Copy constructor.
    Date(const Date& dt)
        { *this = dt; }

    // Destructor.
    virtual ~Date() {}

    // Overloaded assignment operator.
    Date& operator=(const Date& dt)
        { ndays = dt.ndays; return *this; }

    // Overloaded arithmetic operators.
    Date  operator+(int n) const
        { Date dt(*this); dt += n; return dt; }
    Date  operator-(int n) const
        { Date dt(*this); dt -= n; return dt; }
    Date& operator+=(int n)
        { ndays += n; return *this; }
    Date& operator-=(int n)
        { ndays -= n; return *this; }
    Date& operator++()        // prefix
        { ++ndays; return *this; }
    Date  operator++(int)  // postfix
        { Date dt(*this); dt.ndays++; return dt; }
    Date& operator--()        // prefix
        { --ndays; return *this; }
    Date  operator--(int)  // postfix
        { Date dt(*this); dt.ndays--; return dt; }
    long int operator-(const Date& dt) const
        { return ndays-dt.ndays; }
    // --- overloaded relational operators
    bool operator==(const Date& dt) const
        { return ndays == dt.ndays; }
    bool operator!=(const Date& dt) const
        { return ndays != dt.ndays; }
    bool operator< (const Date& dt) const
        { return ndays <  dt.ndays; }
    bool operator> (const Date& dt) const
        { return ndays >  dt.ndays; }
    bool operator<=(const Date& dt) const
        { return ndays <= dt.ndays; }
    bool operator>=(const Date& dt) const
        { return ndays >= dt.ndays; }

    // Getter and setter functions.
    void SetDate(int mo, int da, int yr);
    void SetMonth(int mo)
        { *this = Date(mo, GetDay(), GetYear()); }
    void SetDay(int da)
        { *this = Date(GetMonth(), da, GetYear()); }
    void SetYear(int yr)
        { *this = Date(GetMonth(), GetDay(), yr); }
    void GetDate(int& mo, int& da, int& yr) const;
    int  GetMonth() const;
    int  GetDay()   const;
    int  GetYear() const;

    // Display method.
    virtual void Display() const;

    // Test for leap year.
    bool IsLeapYear(int yr) const
        { return ((yr % 4)==0 && (yr % 1000)!=0); }
    bool IsLeapYear() const
        { return IsLeapYear(GetYear()); }
};

// Overloaded (int + Date)
inline Date operator+(int n, const Date& dt)
{
    return dt + n;
}

#endif