Overloading Equality and Inequality Operators

  
#include <iostream>
using namespace std;
class CDate
{
private:
    int m_nDay;
    int m_nMonth;
    int m_nYear;

   void AddDays (int nDaysToAdd);
   void AddMonths (int nMonthsToAdd);
    void AddYears (int m_nYearsToAdd);

public:

    CDate (int nDay, int nMonth, int nYear)
          : m_nDay (nDay), m_nMonth (nMonth), m_nYear (nYear) {};

    void DisplayDate ()
    {
        cout << m_nDay << " / " << m_nMonth << " / " << m_nYear << endl;
    }

    // integer conversion operator
    operator int();

    // equality operator that helps with: if (mDate1 == mDate2)...
    bool operator == (const CDate& mDateObj);

    // overloaded equality operator that helps with: if (mDate == nInteger)
    bool operator == (int nDateNumber);

    // inequality operator
    bool operator != (const CDate& mDateObj);

    // overloaded inequality operator for integer types
    bool operator != (int nDateNumber);
};

CDate::operator int()
{
   return ((m_nYear * 10000) + (m_nMonth * 100) + m_nDay);
}

// equality operator that helps with if (mDate1 == mDate2)...
bool CDate::operator == (const CDate& mDateObj)
{
    return ( (mDateObj.m_nYear == m_nYear)
            && (mDateObj.m_nMonth == m_nMonth)
           && (mDateObj.m_nDay == m_nDay) );
}

bool CDate::operator == (int nDateNumber)
{
    return nDateNumber == (int)*this;
}

// inequality operator
bool CDate::operator != (const CDate& mDateObj)
{
    return !(this->operator== (mDateObj));
}

bool CDate::operator != (int nDateNumber)
{
    return !(this->operator == (nDateNumber));
}

void CDate::AddDays (int nDaysToAdd)
{
    m_nDay += nDaysToAdd;

   if (m_nDay > 30)
   {
       AddMonths (m_nDay / 30);

       m_nDay %= 30;    // rollover 30th -> 1st
   }
}
void CDate::AddMonths (int nMonthsToAdd)
{
   m_nMonth += nMonthsToAdd;

   if (m_nMonth > 12)
   {
       AddYears (m_nMonth / 12);

       m_nMonth %= 12;    // rollover dec -> jan
   }
}
void CDate::AddYears (int m_nYearsToAdd)
{
   m_nYear += m_nYearsToAdd;
}

int main ()
{
    CDate mDate1 (25, 6, 2008);
    mDate1.DisplayDate ();

    CDate mDate2 (23, 5, 2009);
    mDate2.DisplayDate ();

    if (mDate2 != mDate1)
        cout << "The two dates are not equal... As expected!" << endl;

    CDate mDate3 (23, 5, 2009);
    mDate3.DisplayDate ();

    if (mDate3 == mDate2)
        cout << "mDate3 and mDate2 are evaluated as equals" << endl;

    // Get the integer equivalent of mDate3 using operator int()
    int nIntegerDate3 = mDate3;
    cout << nIntegerDate3<< endl;

    // Use overloaded operator== (for int comparison)
    if (mDate3 == nIntegerDate3)
        cout << "The integer  and mDate3 are equivalent" << endl;

    // Use overloaded operator != that accepts integers
    if (mDate1 != nIntegerDate3)
        cout << "The mDate1 is inequal to mDate3";

    return 0;
 }

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Overloading Equality and Inequality Operators : Compare « Overload « C++

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