c++ negative square root

Question

My goal is to print *** if the square root is negative. But I can't think of a way to change default nan text to ***

for(int i=x1;i<=x2;i++){
   double y = sqrt(pow(i,2)+3*i-500);
    if(y = ?){
        outFile << "***";
    }

So, what should I write in the if statement to make it possible? Or maybe there is another way to check if the y is nan then print *

Answer 1

How about checking for a negative input to the square root function?

for (int i = x1; i <= x2; ++i)
{
    double x = pow(i, 2) + 3*i - 500;
    if (x < 0)
    {
        outFile << "***";
    }
    else
    {
        outFile << sqrt(x);
    }
}