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{-# LANGUAGE DeriveFoldable #-}
module Main where
-- Trying to check if this is null from left to right or right to left
-- will produce an infinite loop.
data Ouch a = Ouch (Ouch a) a (Ouch a) deriving Foldable
ouch :: a -> Ouch a
ouch a = v where v = Ouch v a v
newtype Tuplouch a = Tuplouch (Ouch (a, Int)) deriving Foldable
main :: IO ()
main = do
print $ null (ouch ())
print $ null (Tuplouch (ouch ((), 3)))
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