[Haskell-cafe] instance Enum Double considered not entirely great?

[Richard O'Keefe]

On 26/09/2011, at 11:08 AM, Daniel Fischer wrote:
> 
> And: distinguish NaNs or identify them all?
> I lean towards identifying them all, I've never cared for whether they come 
> from 0/0, Infinity - Infinity or what, but I could be convinced.

There are very many bit patterns that count as NaNs, but only two
classes worth distinguishing: qNaNs and sNaNs.  The payload bits
have no cross-platform significance; if it comes to that, there are
two opposing conventions for which value of the is-it-quiet bit, so
it's not clear if any distinction is worth making.