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Icelandjack/14661.md

Created January 27, 2018 20:43
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GHC Trac 14661
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14661.md 
class ListLike f where
  nil  :: f a
  cons :: a -> f a -> f a
  (·)  :: f a -> f a -> f a

newtype LL a = LL (forall ff. ListLike ff => ff a)

instance ListLike LL where
  nil :: LL a
  nil = LL nil
  
  cons :: a -> LL a -> LL a
  cons a (LL as) = LL (cons a as)
  
  (·) :: LL a -> LL a -> LL a
  LL as · LL bs = LL (as · bs)
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