Returning address to temp var.

Hi.

I recently wrote a matrix class and overloaded the '()' operator for easy access to the elements. I return the address of the selected element for easy modification.

Then I also thought that you might wanna make the element read-only, anyway this was my solution :

Code:

---

double & CMatrix::operator () (int row, int col)
{
        //Err check omitted       

        if (readOnly)
        {
                double tempVal = elements[row][col];
                return tempVal;
        }
       
        return elements[row][col];
}

---

I get a warning when I compile (returning address of local variable...) but I don't know if this would be bad/dangerous in this particular case.

Is this a bad way to do it in this case ? If so why, and what would be a better solution ?

Yes, this is a bad solution because the tempVal variable will go out of scope and a reference to garbage will be returned.

A better way to return read-only might be to make a separate function that is const and returns a const reference. That way you have two functions, one that is read-only and one that isn't. The compiler will figure out which one to use as appropriate.

You could create two seperate overloads, one that returns the value (and therefor read only) and another that returns a reference to the value in the class.

Returning a reference to a local variable is worthless as it is likely a garbage value as soon as the function goes out of scope.