0/0, ∞/∞, ∞%n, n%0, ∞-∞, results with imaginary components

The first five have no meaningful approximation or way to interact with anything. And there's no good way to pretend a single float is a complex number.

So those results get the "this doesn't exist" treatment. Coder's choice if NaN triggers errors or not.

Would you try to define any more behavior for any of those NaNs?