Whatever you choose for that, if it doesn't throw an exception, then given x = 1/0 (or x = something else NaNish) we really should have x == x. Basic equality r

Whatever you choose for that, if it doesn't throw an exception, then given x = 1/0 (or x = something else NaNish) we really should have x == x. Basic equality really needs to be reflexive, or else you're asking for trouble.