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{-# LANGUAGE DataKinds #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE TypeOperators #-}

data Rec :: (a -> *) -> (a -> *) -> [a] -> * where
  RNil :: Rec f g '[]
  (:&) :: (f a -> g a) -> Rec f g as -> Rec f g (a ': as)