Proposal: Add Data.Bits.popCount
ekmett at gmail.com
Wed Aug 17 18:41:43 CEST 2011
+1. I use this operation very heavily in geometric algebra.
On Wed, Aug 17, 2011 at 12:37 PM, Johan Tibell <johan.tibell at gmail.com>wrote:
> Now when we have a fast popCnt# primop* it would be nice to expose it
> to the world through an official API. I propose we add this method to
> the Bits class in Data.Bits:
> -- | Return the number of set bits in the argument, know as the
> -- population count or the Hamming weight.
> popCount :: a -> Int
> I will provide a default implementation, which means that this change
> won't break any existing user defined instances. All the instances for
> the basic types (Ints, Words, etc) will use the primops.
> * These primops compile to a single POPCNT instruction if the user
> compile using -msse4.2 and a fast lookup table based implementation
> Discussion period: 2 weeks
> Libraries mailing list
> Libraries at haskell.org
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