{-# LANGUAGE Safe #-}
{-# OPTIONS_NHC98 --prelude #-}
-- This module deliberately declares orphan instances:
{-# OPTIONS_GHC -fno-warn-orphans #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  Control.Monad.Instances
-- Copyright   :  (c) The University of Glasgow 2001
-- License     :  BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer  :  [email protected]
-- Stability   :  provisional
-- Portability :  portable
--
-- 'Functor' and 'Monad' instances for @(->) r@ and
-- 'Functor' instances for @(,) a@ and @'Either' a@.

module Control.Monad.Instances (Functor(..),Monad(..)) where

import Prelude

instance Functor ((->) r) where
        fmap = (.)

instance Monad ((->) r) where
        return = const
        f >>= k = \ r -> k (f r) r

instance Functor ((,) a) where
        fmap f (x,y) = (x, f y)

instance Functor (Either a) where
        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