+{-# OPTIONS_NHC98 --prelude #-}
+-- This module deliberately declares orphan instances:
+{-# OPTIONS_GHC -fno-warn-orphans #-}
-----------------------------------------------------------------------------
-- |
-- Module : Control.Monad.Instances
-- 'Functor' and 'Monad' instances for @(->) r@ and
-- 'Functor' instances for @(,) a@ and @'Either' a@.
-module Control.Monad.Instances () where
+module Control.Monad.Instances (Functor(..),Monad(..)) where
import Prelude
instance Functor ((->) r) where
- fmap = (.)
+ fmap = (.)
instance Monad ((->) r) where
- return = const
- f >>= k = \ r -> k (f r) r
+ return = const
+ f >>= k = \ r -> k (f r) r
instance Functor ((,) a) where
- fmap f (x,y) = (x, f y)
+ fmap f (x,y) = (x, f y)
instance Functor (Either a) where
- fmap _ (Left x) = Left x
- fmap f (Right y) = Right (f y)
+ fmap _ (Left x) = Left x
+ fmap f (Right y) = Right (f y)
+
+instance Monad (Either e) where
+ return = Right
+ Left l >>= _ = Left l
+ Right r >>= k = k r