[r6rs-discuss] Re: [Formal] eq?/eqv? misbehave around NaNs

From: Alan Watson <alan>
Date: Fri Nov 24 17:13:54 2006

Marcin 'Qrczak' Kowalczyk wrote:
> Alan Watson <alan_at_alan-watson.org> writes:
>>Can you give examples of why requiring
>>(eqv? +nan.0 +nan.0) to be true and (eqv? 1f0 1d0) to be false are
>>useful?
>
> Memoization (of pure functions).

Good one. I may be on the point of conceding (eqv? +nan.0 +nan.0).

>>Can you come up with a description of eqv? that obtains the behaviour
>>you want on singles and doubles without reference to their
>>representation?
>
> What does "singles" and "doubles" mean, if you are not allowed to
> refer to the representation?

They refer to, for example, the behaviour on the application of the
standard arithmetic operations. I gave an example earlier of looking at
the behaviour when you attempt to force a single-precision overflow.

Regards,

Alan
Received on Fri Nov 24 2006 - 17:13:25 UTC