You can work in the ring of dual numbers, where ε is a nilpotent and hence noninvertible (which is okay, because it's not a field!) and it's a perfectly rationa

You can work in the ring of dual numbers, where ε is a nilpotent and hence noninvertible (which is okay, because it's not a field!) and it's a perfectly rational (hehe) number system to work in. https://en.wikipedia.org/wiki/Dual_number https://en.wikipedia.org/wiki/Dual_number