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import Test.IOSpec
import Test.QuickCheck
readOnce :: Int -> IOSpec IORefS Int
readOnce x = do ref <- newIORef x
readIORef ref
readTwice :: Int -> IOSpec IORefS Int
readTwice x = do ref <- newIORef x
readIORef ref
readIORef ref
readIORefProp :: Int -> Bool
readIORefProp x =
let once = evalIOSpec (readOnce x) singleThreaded
twice = evalIOSpec (readTwice x) singleThreaded
in once == twice
main = quickCheck readIORefProp
instance Eq a => Eq (Effect a) where
(Done x) == (Done y) = x == y
_ == _ = error "Incomparable effects."
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