semigroupoids-1.3.2: Data/Traversable/Instances.hs

{-# LANGUAGE CPP #-}
-- | Placeholders for missing instances of Traversable, until base catches up and adds them
{-# OPTIONS_GHC -fno-warn-orphans #-}
module Data.Traversable.Instances where

#if !(MIN_VERSION_transformers(0,3,0))
import Control.Monad.Trans.Identity
import Data.Foldable
import Data.Traversable

instance Foldable m => Foldable (IdentityT m) where
  foldMap f = foldMap f . runIdentityT

instance Traversable m => Traversable (IdentityT m) where
  traverse f = fmap IdentityT . traverse f . runIdentityT
#endif