[lamontcg]

FWIW, I tend to write a lot of error checking code that checks for division by zero ahead of time and just returns zero instead. Found an example:

        public double magnitude
        {
            get
            {
                double c = max_magnitude;
                return c > 0 ? Math.Max(c, c * (this / c)._internal_magnitude) : 0;
            }
        }

I could delete quite a few if statements in pretty hot codepaths if division by zero just returned zero.

[xxpor]

This feels like an area where extended/vector instructions could be added to make this fast too. Probably not news to you, but for example, NEON (and likely AVX, I’m just a lot less familiar with it) has saturating addition and subtraction.