Overloading Operators for Derived Classes

[Brett Stott]

I have an assignment to derive a Runner class from a Period class. A Period consists of hours(int), minutes(int), and seconds(float) and is in the format of hh:mm:ss.s. A Runner is a Period with a name. We've been given this main function and we have to write the two classes to make it work properly.

int main( ){
	Runner runners[100];
	int count;
	ifstream fin;
	fin.open("f:\\TOU.txt");
	fin >> count;
	for (int n=0; n<count; n++)
		fin >> runners[n];
	Sort (runners, count);
	cout << "  NAME    TIME    OFF PACE\n";
	for (int n=0; n<count; n++)
		cout << runners[n] << runners[0] – runners[n] << endl;
}

I have the input and output operators overloaded right, but I can't seem to get that minus operator to subtract the two Runners, but only display the Period. My overloaded output for Runners makes it output the name, then a tab, then the Period.

This is the in-class overloaded minus that I tried.

Runner& operator-(const Runner&); //in Public of the Runner class

Runner& Runner::operator-(const Runner& r){
	this->setTotal(getTotal() - r.getTotal());
	this->totalConvert();
	return *this;
}

And here's the stand alone one that I tried. The if statement is just how I'm going to display the difference as a negative, since I don't want to let a Period be negative on its own. I'll just have the output function put a negative on the front if neg==true.

Period operator-(Runner a, Runner b);

Period operator-(Runner a, Runner b){
	Period temp;
	if(a.getTotal()>b.getTotal()){
		temp.setTotal(a.getTotal() - b.getTotal());
	}
	else if(b.getTotal()>a.getTotal()){
		temp.setTotal(b.getTotal() - a.getTotal());
		neg=true;
	}
	else
		temp.setTotal(0);
	temp.totalConvert();
	return temp;
}

The getTotal function converts the hours, minutes, and seconds into seconds as one big float. The totalConvert puts it back into hours, minutes, and seconds so I don't have to worry about converting it during the subtraction.

Even just a hint at what I might be doing wrong would be awesome so that you're not just giving me the answer. I do actually want to learn it, but I have no idea why I can't even get passed the syntax error on the subtraction in main().

The file that it reads in is this.

5
Fred Smith 	3:21:19
Jane Doe	3:45:58
Sam Black	2:59:14
Dan Green	4:10:21
Bob Jones	3:58:18

If you need to see any other parts (or all) of my code, let me know.

[ne555]

I can't even get passed the syntax error on the subtraction in main().

¿what does the error say?

Runner& operator-(const Runner&); is counter intuitive, you're modifying the operand.
In Period operator-(Runner a, Runner b); ¿where is `neg' defined?

Instead of operating in `Runner' you could operate in `Period', after all a runner is a period (¿?)

[Brett Stott]

The error is saying that it expected a semicolon instead of the hyphen.

Neg is a private variable in Runner, so I guess a Runner is a Period with a name and the neg flag.

I've tried doing it in Period too, but it was a member function and didn't prevent the syntax error.

[Brett Stott]

So it turns out that when I copied and pasted the main.cpp from the .doc that we were given, it made the hyphen some random symbol that just looks like a hyphen. I replaced it with a real one and it works fine.