Randomly generated a list of n 16-bit Integers, sum up their set bits.

set-bits-int16.hs

import System.Environment (getArgs)
import System.Random (StdGen, newStdGen, random)
import Data.Bits (popCount)
import Data.List (unfoldr)
import Data.Int (Int16)

main = do
  seed <- newStdGen
  args <- getArgs
  let size  = read $ head args
  let rands = randomlist size seed
  print $ sum $ map popCount rands

randomlist :: Int -> StdGen -> [Int16]
randomlist n = take n . unfoldr (Just . random)

--  $ runhaskell set-bits-int16.hs 1000000
--  8000183