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import System.IO.Unsafe (unsafePerformIO)
data T = T !Bool
data Box a = Box a
f :: Int -> T -> Box Bool
f n t
| n <= 0 = case t of
T b -> Box b
| otherwise = f (n-2) t
f1 :: Int -> Bool -> Box Bool
f1 n t
| n <= 0 = f (-n) $! T t
| otherwise = f1 (n-2) t
g :: Int -> Bool
g k = if k <= 0
then unsafePerformIO (putStrLn "Evaluated True" >> return True)
else unsafePerformIO (putStrLn "Evaluated False" >> return False)
{-# NOINLINE g #-}
main :: IO ()
main = case f1 4 (g 0) of
Box _ -> return ()
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