-- |
-- Module : Data.Monoid
-- Copyright : (c) Andy Gill 2001,
--- (c) Oregon Graduate Institute of Science and Technology, 2001
+-- (c) Oregon Graduate Institute of Science and Technology, 2001
-- License : BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer : libraries@haskell.org
mempty = ()
_ `mappend` _ = ()
mconcat _ = ()
+
+instance (Monoid a, Monoid b) => Monoid (a,b) where
+ mempty = (mempty, mempty)
+ (a1,b1) `mappend` (a2,b2) =
+ (a1 `mappend` a2, b1 `mappend` b2)
+
+instance (Monoid a, Monoid b, Monoid c) => Monoid (a,b,c) where
+ mempty = (mempty, mempty, mempty)
+ (a1,b1,c1) `mappend` (a2,b2,c2) =
+ (a1 `mappend` a2, b1 `mappend` b2, c1 `mappend` c2)
+
+instance (Monoid a, Monoid b, Monoid c, Monoid d) => Monoid (a,b,c,d) where
+ mempty = (mempty, mempty, mempty, mempty)
+ (a1,b1,c1,d1) `mappend` (a2,b2,c2,d2) =
+ (a1 `mappend` a2, b1 `mappend` b2,
+ c1 `mappend` c2, d1 `mappend` d2)
+
+instance (Monoid a, Monoid b, Monoid c, Monoid d, Monoid e) =>
+ Monoid (a,b,c,d,e) where
+ mempty = (mempty, mempty, mempty, mempty, mempty)
+ (a1,b1,c1,d1,e1) `mappend` (a2,b2,c2,d2,e2) =
+ (a1 `mappend` a2, b1 `mappend` b2, c1 `mappend` c2,
+ d1 `mappend` d2, e1 `mappend` e2)
+
+-- lexicographical ordering
+instance Monoid Ordering where
+ mempty = EQ
+ LT `mappend` _ = LT
+ EQ `mappend` y = y
+ GT `mappend` _ = GT