Right - I was aiming for something analogous to your rule, which has the condition of even inputs. I do prefer your simpler example. Either way, I'm not sure yo

Right - I was aiming for something analogous to your rule, which has the condition of even inputs. I do prefer your simpler example. Either way, I'm not sure your rhetorical strategy would be persuasive to someone who was unsure of the parity of zero (because, as you say, zero is an exceptional number).