Highly optimized and accurate vector subscript operator

class BWAVector3
{
private:
                float x;
                float y;
                float z;
public:
...
 
                float& operator[] (const int index);
};
float& BWAVector3::operator[] (const int index)
{
                if (index == 0)
                {
                                return x;
                }
                else if (index == 1)
                {
                                return y;
                }
                else
                {
                                return z;
                }
}

(Thanks for the submission Graham Wihlidal)