[Haskell-beginners] Int V.S. Word32

[Haisheng Wu]

Hello,
  I got great performance difference for the following code if I used type
`Int` rather than `Data.Word.Word32`.
  Anyone can help to explain why such difference?
  Thanks a lot.

-Simon

module Main where
import Data.Word

main :: IO ()
main = print $ p14

p14 = maximum [ (startChain n 0, n) | n <- [2..1000000] ]

startChain :: Word32 -> Int -> Int
startChain 1 count    = count + 1
startChain n count    = startChain (intTransform n) (count+1)

intTransform :: Word32 -> Word32
intTransform n
  | even n         = n `div` 2
  | otherwise      = 3 * n + 1
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