The longer the Arnold-Nate PingPong match lasts, the more I become
convinced that it is a battle about nothing. The decoration at the
end of a long computation gives a summary of what may have gone wrong,
and to find out the detail, one retries it, checking at every step, or
(if the system supports it) in a mode that makes certain conditions
trigger a synchronous trap, with operands made available to the trap
handler. So Arnold's scheme lumps certain conditions together that
Nates' distinguishes -- but I doubt ALL distinctions are made, so in
general operands of suspicious operations have to be inspected anyway,
at which point full discrimination is possible.
So if Arnold's scheme has other advantages, they should not be discarded
because of this quibble between undefined, ill-defined and empty.