[Haskell-beginners] How to call popCnt64#?

[John Ky]

Hi Michael,

Yes, that did the trick.

Thanks!

-John

On Mon, 21 Mar 2016 at 01:13 Michael Snoyman <michael at snoyman.com> wrote:

> Here's an example:
>
> {-# LANGUAGE MagicHash #-}
> import GHC.Prim
> import GHC.Types
> import Data.Word
>
> main :: IO ()
> main = do
>     let word = 5 :: Word
>         res =
>             case word of
>                 W# w -> W# (popCnt64# w)
>     print res
>
>
> On Sun, Mar 20, 2016 at 12:19 PM, John Ky <newhoggy at gmail.com> wrote:
>
>> Hello Haskellers,
>>
>> Does anyone know how to call popCnt64# from the GHC.Prim module?
>>
>> This was my failed attempt:
>>
>> λ> popCnt64# 1
>>
>>
>> <interactive>:14:11:
>> Couldn't match kind ‘*’ with ‘#’
>> When matching types
>> a0 :: *
>> Word# :: #
>> Expected type: Integer -> Word#
>> Actual type: Integer -> a0
>> In the first argument of ‘popCnt64#’, namely ‘1’
>> In the expression: popCnt64# 1
>> In an equation for ‘it’: it = popCnt64# 1
>>
>> -John
>>
>>
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>>
>>
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