Re: Proposal: Remove Num superclass of Bits

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 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 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@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@joachim-breitner.de | nomeata@debian.org | GPG: 0x4743206C xmpp: nomeata@joachim-breitner.de | http://www.joachim-breitner.de/

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