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@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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