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{-# LANGUAGE DeriveFoldable #-}
module Main where
import Data.Semigroup
-- Just a list without any special fusion rules.
data List a = Nil | Cons a (List a) deriving Foldable
instance Semigroup (List a) where
Nil <> ys = ys
Cons x xs <> ys = Cons x (xs <> ys)
replicateList :: Int -> a -> List a
replicateList 0 x = Nil
replicateList n x = Cons x (replicateList (n - 1) x)
newtype ListList a = ListList (List (List a)) deriving Foldable
long :: Int -> Bool
long n = null $ ListList $ replicateList n Nil <> Cons (Cons () Nil) Nil
main :: IO ()
main = print $ long (10^(6 :: Int))
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