Comment by gnosek

I agree with all your other points but

> > We can’t perform arithmetic on an Option<int> any more than we could on a List<int>.

> Why not? One sensible definition is (...)

It's not the only sensible definition. It would be equally sensible to implement it as:

    Some(x) + Some(y) => Some(x+y)
    Some(x) + None => Some(x)
    None + Some(y) => Some(y)
    None + None => None