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

Chris Smith cdsmith at gmail.com
Wed Sep 21 00:11:21 CEST 2011

On Wed, 2011-09-21 at 00:04 +0200, Ketil Malde wrote:
> > If Haskell defined list syntax in terms of something that's not called
> > Enum, that would be fine.  Renaming is never all that big a deal.  But
> > the list sugar is a big deal, and I don't think there's any point at all
> > in leaving the list sugar associated with something as minor as building
> > a representation of the inaccuracy of your approximations.
> I must admit I don't understand this comment.  If the fixpoint library
> wants to provide the functionality (producing all values between two
> points), and can't/shouldn't use Enum, surely it must provide a
> different function, and let go of the list sugar?

Sorry to be unclear.  I mean that instead of removing a useful instance,
if people find the use of Enum for Float to be objectionable, then
perhaps (via language extensions, deprecation, all the usual backward
compatibility slow-change stuff) the desugaring of list ranges should be
changed to not use something with a name you'd object to, rather than
just removing the feature.

In any case, as long as Enum *is* the backing for list desugaring, it
seems like a mistake to define instances that are completely unuseful
for list desugaring.


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