What does my error mean?

[Sean TMD]

Hi, I'm new to C++ and this website. I have come here before for help with my coding but I could not find the answer I needed for my current problem. I am receiving the error "illegal, left operand has type "double" and "illegal, right operand type has "double" in the line where the standard_dev equation is displayed.

I have seen this error fixed before on this site but the code was too complicated for me to understand why it occurred and how it was fixed.

using namespace std;
void my_statistics(double x1, double x2, double x3, double x4);
void output(double average, double standard_dev);

double x1, x2, x3, x4, average, standard_dev;

int main()
{

	cout.setf(ios::fixed);
	cout.precision(4);

	cout<<" Input the values for x1 through x4 "<<endl;
	cin>>x1>>x2>>x3>>x4;
	my_statistics(x1, x2, x3, x4);
	output(average, standard_dev);

return 0;
}
////////////////////////////////////////////////////
void my_statistics(double x1, double x2, double x3, double x4, double average, double standard_dev)
	{
		average = 0;
		standard_dev = 0;

average = (x1 + x2 + x3 + x4) / 4;
standard_dev = sqrt(((x1 - average) ^ 2 + (x2 - average) ^ 2 + (x3 - average) ^ 2 +(x4 - average) ^ 2) / 3);
	}

If possible I would like the type to remain as double. As a bonus question, would I use a loop or if statement if I wanted to make the code tell the user to input numbers until they type "n" (at which point the code would move on)?

Thanks for your help.

[LB]

Could you be more specific about which line the error is on? Also, you need to copy and paste the exact text of the error - never paraphrase.

Sean TMD wrote:

As a bonus question, would I use a loop or if statement if I wanted to make the code tell the user to input numbers until they type "n" (at which point the code would move on)?

std::cout << "Enter numbers, then enter 'n' to continue." << std::endl;
std::string input;
while(std::cin >> input && input != "n")
{
    int n;
    if(std::istringstream(input) >> n)
    {
        //do something with n, e.g.:
        my_vector.push_back(n);
    }
}

[Sean TMD]

Yes, sorry about that. The error is occuring in line 27 and the error is:

1>c:\users\user\documents\visual studio 2008\projects\standard dev\standard dev\hw.cpp(34) : error C2296: '^' : illegal, left operand has type 'double'
1>c:\users\user\documents\visual studio 2008\projects\standard dev\standard dev\hw.cpp(34) : error C2297: '^' : illegal, right operand has type 'double'

Also thank you for your response.

[LB]

I edited my post with an answer to your bonus question.

As for the error you are getting, it is because you are using the XOR operator (the ^ operator is not exponentiation, but instead bitwise XOR). You need to #include <cmath> and use std::pow instead.

[Sean TMD]

Ahhh, thank you so much. That didn't even occur to me. I still have a lot to learn. Thanks again. The code worked after your suggestions.