    {-# LANGUAGE CPP #-}

    #if __GLASGOW_HASKELL__ >= 708
    {-# LANGUAGE DeriveDataTypeable #-}
    #endif

    -----------------------------------------------------------------------------
    -- |
    -- Copyright   :  (C) 2008-2015 Edward Kmett
    -- License     :  BSD-style (see the file LICENSE)
    --
    -- Maintainer  :  Edward Kmett <ekmett@gmail.com>
    -- Stability   :  provisional
    -- Portability :  portable
    --
    ----------------------------------------------------------------------------
    module Data.Bifunctor.Tannen
      ( Tannen(..)
      ) where

    #if __GLASGOW_HASKELL__ < 710
    import Control.Applicative
    #endif

    import Data.Biapplicative
    import Data.Bifoldable
    import Data.Bitraversable

    #if __GLASGOW_HASKELL__ < 710
    import Data.Foldable
    import Data.Monoid
    import Data.Traversable
    #endif

    #if __GLASGOW_HASKELL__ >= 708
    import Data.Typeable
    #endif

    -- | Compose a 'Functor' on the outside of a 'Bifunctor'.
    newtype Tannen f p a b = Tannen { runTannen :: f (p a b) }
      deriving ( Eq, Ord, Show, Read
    #if __GLASGOW_HASKELL__ >= 708
               , Typeable
    #endif
               )

    instance (Functor f, Bifunctor p) => Bifunctor (Tannen f p) where
      first f = Tannen . fmap (first f) . runTannen
      {-# INLINE first #-}
      second f = Tannen . fmap (second f) . runTannen
      {-# INLINE second #-}
      bimap f g = Tannen . fmap (bimap f g) . runTannen
      {-# INLINE bimap #-}

    instance (Functor f, Bifunctor p) => Functor (Tannen f p a) where
      fmap f = Tannen . fmap (second f) . runTannen
      {-# INLINE fmap #-}

    instance (Applicative f, Biapplicative p) => Biapplicative (Tannen f p) where
      bipure a b = Tannen (pure (bipure a b))
      {-# INLINE bipure #-}

      Tannen fg <<*>> Tannen xy = Tannen ((<<*>>) <$> fg <*> xy)
      {-# INLINE (<<*>>) #-}

    instance (Foldable f, Bifoldable p) => Foldable (Tannen f p a) where
      foldMap f = foldMap (bifoldMap (const mempty) f) . runTannen
      {-# INLINE foldMap #-}

    instance (Foldable f, Bifoldable p) => Bifoldable (Tannen f p) where
      bifoldMap f g = foldMap (bifoldMap f g) . runTannen
      {-# INLINE bifoldMap #-}

    instance (Traversable f, Bitraversable p) => Traversable (Tannen f p a) where
      traverse f = fmap Tannen . traverse (bitraverse pure f) . runTannen
      {-# INLINE traverse #-}

    instance (Traversable f, Bitraversable p) => Bitraversable (Tannen f p) where
      bitraverse f g = fmap Tannen . traverse (bitraverse f g) . runTannen
      {-# INLINE bitraverse #-}