C++ Best way to handle division by zero

Question

I'm writing a C++ class that stores some double values in a vector (called mpValues) and calculates their average. When constructed, the value array is empty, so performing this calculation would return 0.0/0.0.

I decided that asking for the mean of zero values is a error. Therefore, it would be best to return NaN and display an error message, so that the user is made aware of that problem. The code looks like this:

double Average::CalculateAverage() const
{
    if(mpValues->size() == 0){
        std::cerr << "Instance of Average at: " << this << " contains no values.\n"
                  << "In this case the arithmetic mean is defined as NaN." <<std::endl;

        return 0.0/0.0;
    }
    else{
        ...calculate the arithmetic mean
    }
}

Is this a sensible approach, or do you have better suggestions? Usually, I wouldn't be so fussy, but this is a test for a job offer so I'd like to avoid bad decisions.

Thanks in advance!

Answer 1

The standard options are to return NaN, throw an exception, or return an option, such as boost::optional. There are advantages and disadvantages to each, which have been reviewed in detail by numerous people. Just do not display error messages within the function, since this violates the single responsibility principle.