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Overloaded Operators

paulr162 (12)
Hello,

I am having an issue getting my overloaded postfix operators ++ and -- to work inside my class. Here is my entire class:

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class NumDays
{
	private:
		int hours;
	public:
		NumDays();
		NumDays(int);
		NumDays(double);

		void setHours (int);
		void setDays (double);
		int getHours();
		double getDays();
		operator double(); 
		NumDays operator+ (NumDays&);
		NumDays operator- (NumDays&);
		NumDays& operator++ ();
		NumDays& operator-- ();
		NumDays operator++ (int);
		NumDays operator-- (int);
};

//********************************************

NumDays::NumDays()
{
	hours = 0;
}

//********************************************

NumDays::NumDays (int time)
{
	hours = time;
}

//********************************************

NumDays::NumDays (double days)
{
	hours = days * 8;
}

//********************************************

void NumDays::setHours (int numHours)
{
	numHours = hours;
}

//********************************************

void NumDays::setDays (double d)
{
	hours = d * 8;
}

//********************************************

int NumDays::getHours ()
{
	return hours;
}

//********************************************

double NumDays::getDays ()
{
	double days;
	days = (hours / 8);
	return days;
}

//********************************************

NumDays::operator double ()
{
	double x;
	x = hours/8.0;
	return x;
}

//********************************************

NumDays NumDays::operator+ (NumDays& a)
{
	NumDays b;
	b.hours = this->hours + a.hours;
	return b;
}

//********************************************

NumDays NumDays::operator- (NumDays& a)
{
	NumDays b;
	b.hours = this->hours - a.hours;
	return b;
}

//********************************************

NumDays& NumDays::operator++ ()
{
	++hours;
	return *this;
}

//********************************************

NumDays& NumDays::operator-- ()
{
	--hours;
	return *this;
}

//********************************************

NumDays NumDays::operator++ (int)
{
	hours++;
	return hours;
}

//********************************************

NumDays NumDays::operator-- (int)
{
	hours--;
	return hours;
}


Whenever I use this class and use the ++ postfix operator, it acts like a prefix operator. What could I do to fix my code to get the postfix operator working?

Thanks for any and all help!
Disch (13742)
Whenever I use this class and use the ++ postfix operator, it acts like a prefix operator.


That's because the two are doing the same thing ;P

The postfix operator needs to remember the "old" value and return that. This is usually done by making a copy of it:

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NumDays NumDays::operator++ (int)
{
  NumDays copy( *this );
  ++hours;
  return copy;
}


This is also why the postfix operators can't return a reference like the prefix operators can -- because they have to return that copy and not *this.
paulr162 (12)
Thank you for your help! I really appreciate it. I have a question regarding the NumDays copy( *this ); line. What exactly does this line do? Is it creating an object of type NumDays called copy. If so, what is the *this pointer filling in?

Thanks again.
Angeljruiz (187)
Its making a copy of the NumDays object the postfix operator is being used on
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