Proposal: Remove Num superclass of Bits

[Edward Kmett]

We could go with bitDefault popCountDefault, testBitDefault to mirror the
fmapDefault and foldMapDefault in Data.Traversable, but I don't particularly
care which color we paint this bikeshed.

-Edward

On Mon, Oct 17, 2011 at 1:29 PM, Bas van Dijk <v.dijk.bas at gmail.com> wrote:

> I agree.
>
> We should then also drop the default implementation of popCount.
>
> What about adding and exporting helper functions like Ian mentioned:
>
> numBit :: (Bits a, Num a) => Int -> a
> numBit i = 1 `shiftL` i
> {-# INLINE numBit #-}
>
> numPopCount :: (Bits a, Num a) => a -> Int
> numPopCount = go 0
>   where
>    go !c 0 = c
>    go c w = go (c+1) (w .&. w - 1)
>
> numTestBit ::  (Bits a, Num a) => a -> Int -> Bool
> x `numTestBit` i = (x .&. bit i) /= 0
> {-# INLINE numTestBit #-}
>
> Not sure about the names though?
>
> On 17 October 2011 19:12, Edward Kmett <ekmett at gmail.com> wrote:
> > I have to admit this seems to be the most sensible solution, and avoids
> > stealing names that are more appropriate for numeric instances anyways.
> > -Edward
> >
> > On Mon, Oct 17, 2011 at 3:26 AM, Joachim Breitner <
> mail at joachim-breitner.de>
> > wrote:
> >>
> >> Hi,
> >>
> >> Am Samstag, den 15.10.2011, 17:41 -0700 schrieb John Meacham:
> >> > I would just remove the bit and testBit defalut instances, they seem
> >> > like reasonable primitives to be required for an instance.
> >>
> >> I agree. Bits is certainly not something that a Haskell Beginner would
> >> have to implement every day, but is more likely a task that requires
> >> lots of thought and well-written code anyway. Having to implement these
> >> two functions as well is not a large burden there.
> >>
> >> Greetings,
> >> Joachim
> >>
> >> --
> >> Joachim "nomeata" Breitner
> >>  mail at joachim-breitner.de  |  nomeata at debian.org  |  GPG: 0x4743206C
> >>  xmpp: nomeata at joachim-breitner.de | http://www.joachim-breitner.de/
> >>
> >>
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> >
> >
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