Game loop - looping with a fixed delay in Haskell until a condition is met

TimerLoop.hs

module TimerLoop where

import Control.Monad.Loops (iterateUntilM)
import Control.Concurrent (threadDelay)

-- Adapted from https://stackoverflow.com/questions/19285691/how-do-i-write-a-game-loop-in-haskell
--
-- NB must compile with -threaded option or the threadDelay has no apparent effect
-- even, then 9 and 10 are printed out simultaneously on my Windows 7 machine (GHCi 7.8.3)

type World = Int
initWorld :: World
initWorld = 1

-- False when the user wants to exit the game
keepGoing :: World -> Bool
keepGoing w = (>= 10)

displayWorld :: World -> IO ()
displayWorld = print
             
gameLoop :: World -> World
gameLoop = (+1)

main :: IO World
main = iterateUntilM keepGoing displayLoop initWorld
   where displayLoop w = do
           threadDelay 1000000 -- microseconds not millis!
           displayWorld w >> return (gameLoop w)