Problem with << operator

[thechad90000]

I'm working on problem 6 of Euler but the issue I'm having isn't necessarily related to the answer to the problem. I'm attempting to solve the problem using OOP because I really need to get better at it and I keep receiving this error after trying to compile:

error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'Euler6' (or there is no acceptable conversion)

Here is my code that I have.

#include <iostream>

using namespace std;

class Euler6{
	float x;
public:
	Euler6 ();
	float sumofsquares (float);
	float squareofsum (float);
	Euler6 operator - (Euler6);
};


Euler6 Euler6::operator- (Euler6 param){
	Euler6 temp;
	
	temp.x = x - param.x;

	return temp;
}


float Euler6::sumofsquares (float x){
	
	float sum = 0;

	while (x <= 100)
	{
		sum += pow(x,2);
	}

	return sum;
}

float Euler6::squareofsum (float x){

	float sum = 0;

	while (x <= 100)
	{
		sum += x;
	}

	sum = pow(sum, 2);

	return sum;
}

Euler6::Euler6 (){
	x = 1;
}

int main (){
	Euler6 x;
	Euler6 y;
	Euler6 z;
	
	x.sumofsquares (1.0);
	y.squareofsum (1.0);

	z = y - x;


	cout << "The difference is: " << z;

	return 0;
}

Any help as to what I can do to fix this error would be greatly appreciated.

[Catfish2]

You need to overload operator<< to work with your Euler6 class.

// global overload, not inside Euler6 (prototype)
ostream & operator << (ostream &, const Euler6 &);

http://www.parashift.com/c++-faq-lite/input-output.html#faq-15.8

Edit: there are other approaches... like:
- making your float x; public and simply cout << z.x;
- writing a conversion operator like operator float() const {return x;}

[thechad90000]

Thanks a lot it works fine now. I did this:

friend std::ostream& operator << (std::ostream& out, Euler6 const& euler);

std::ostream& operator << (std::ostream& out, Euler6 const& euler)
{
	return out << euler.x;
}

I also fixed the infinite loops I had above and they are producing the correct results but how do I get them to send the correct numbers back to the main program. When I run the program and debug it, it shows that the correct values are going into sum but when I return sum the value of x and y becomes 1 and it keeps saying my difference is zero.

[doug4]

You never assign the sum value to anything persistent. You calculate the sum value in a local value in each function, and then return the sum. The returned value is ignored (you never do anything with it.) You never re-assigned the x value in either "x" or "y" (by the way, consider renaming something so you don't have "x" as an Euler6 object and "x" and as a data member).

So, when you return from the 2 function calls, "x" and "y" are unchanged.

You must either modify ".x" in your functions or capture the return values from the function calls.

[thechad90000]

Perfect. Thank you so much for your explanation. Everything works well now. I just changed the functions to void and assigned sum to x.

Thank you for your help..both of you.