Remove Enum from Float and Double
Roman Cheplyaka
roma at ro-che.info
Wed Jun 12 00:00:48 CEST 2013
Does such thing as a deprecation pragma for an instance exist?
What triggers it?
Roman
* Johan Tibell <johan.tibell at gmail.com> [2013-06-11 14:18:41-0700]
> If we truly believe that the instance is dangerous for users (and not
> merely for people who don't understand floating point arithmetic on
> computers), then we should add a deprecation pragma to the instance and
> discourage its use. But what would the deprecation message encourage
> instead, for users to write an explicit loop that tests against some
> lower/upper bound? It would have the same problem as enumFromTo. I think
> the issue here is really that floating point math on computers is hard to
> think about.
>
>
> On Tue, Jun 11, 2013 at 11:18 AM, harry <voldermort at hotmail.com> wrote:
>
> > Johan Tibell <johan.tibell at ...> writes:
> >
> > > I don't see much gain. It will break previously working code and the
> > workaround to the breakage will likely be manually reimplementing
> > enumFromTo
> > in each instance.
> >
> > I forgot the main point of my post :-)
> >
> > The primary motivation for removing these instances is that they cause
> > endless confusion for beginners, e.g.
> >
> > http://stackoverflow.com/questions/13203471/the-math-behind-1-0999999999999999-in-haskell
> > ,
> > http://stackoverflow.com/questions/9810002/floating-point-list-generator,
> > http://stackoverflow.com/questions/7290438/haskell-ranges-and-floats,
> >
> > http://stackoverflow.com/questions/10328435/how-to-solve-floating-point-number-getting-wrong-in-list-haskell
> > ,
> > and many more.
> >
> > On the other hand, how much working code is there "correctly" using there
> > instances?
> >
> >
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