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Created April 5, 2012 22:24
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gistfile1.hs
module Kuulaskuri (luo, monesko, seuraava) where
import Data.IORef
newtype Kuulaskuri = Kuulaskuri (IORef Int)
luo :: IO Kuulaskuri
luo = do
c <- newIORef 1
return $ Kuulaskuri c
monesko :: Kuulaskuri -> IO Int
monesko (Kuulaskuri r) = readIORef r
seuraava :: Kuulaskuri -> IO ()
seuraava (Kuulaskuri r) = modifyIORef r $ \kuu -> ((kuu `mod` 12) + 1)
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