    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Data.Bifunctor.Clown
    -- Copyright   :  (C) 2008-2013 Edward Kmett,
    -- License     :  BSD-style (see the file LICENSE)
    --
    -- Maintainer  :  Edward Kmett <ekmett@gmail.com>
    -- Stability   :  provisional
    -- Portability :  portable
    --
    -- From the Functional Pearl \"Clowns to the Left of me, Jokers to the Right: Dissecting Data Structures\"
    -- by Conor McBride.
    ----------------------------------------------------------------------------
    module Data.Bifunctor.Clown
      ( Clown(..)
      ) where

    import Control.Applicative
    import Data.Biapplicative
    import Data.Bifunctor.Apply
    import Data.Bifoldable
    import Data.Bitraversable
    import Data.Foldable
    import Data.Functor.Apply
    import Data.Monoid
    import Data.Semigroup.Bifoldable
    import Data.Semigroup.Bitraversable
    import Data.Semigroup.Foldable
    import Data.Semigroup.Traversable
    import Data.Traversable

    -- | Make a 'Functor' over the first argument of a 'Bifunctor'.
    newtype Clown f a b = Clown { runClown :: f a }
      deriving (Eq,Ord,Show,Read)

    instance Functor f => Bifunctor (Clown f) where
      first f = Clown . fmap f . runClown
      {-# INLINE first #-}
      second _ = Clown . runClown
      {-# INLINE second #-}
      bimap f _ = Clown . fmap f . runClown
      {-# INLINE bimap #-}

    instance Functor (Clown f a) where
      fmap _ = Clown . runClown
      {-# INLINE fmap #-}

    instance Applicative f => Biapplicative (Clown f) where
      bipure a _ = Clown (pure a)
      {-# INLINE bipure #-}

      Clown mf <<*>> Clown mx = Clown (mf <*> mx)
      {-# INLINE (<<*>>) #-}

    instance Apply f => Biapply (Clown f) where
      Clown fg <<.>> Clown xy = Clown (fg <.> xy)
      {-# INLINE (<<.>>) #-}

    instance Foldable f => Bifoldable (Clown f) where
      bifoldMap f _ = foldMap f . runClown
      {-# INLINE bifoldMap #-}

    instance Foldable (Clown f a) where
      foldMap _ = mempty
      {-# INLINE foldMap #-}

    instance Traversable f => Bitraversable (Clown f) where
      bitraverse f _ = fmap Clown . traverse f . runClown
      {-# INLINE bitraverse #-}

    instance Traversable (Clown f a) where
      traverse _ = pure . Clown . runClown
      {-# INLINE traverse #-}

    instance Foldable1 f => Bifoldable1 (Clown f) where
      bifoldMap1 f _ = foldMap1 f . runClown
      {-# INLINE bifoldMap1 #-}

    instance Traversable1 f => Bitraversable1 (Clown f) where
      bitraverse1 f _ = fmap Clown . traverse1 f . runClown
      {-# INLINE bitraverse1 #-}