[project @ 2005-02-13 10:53:13 by malcolm]

[ghc-base.git] / Data / Monoid.hs

diff --git a/Data/Monoid.hs b/Data/Monoid.hs
index a328639..cfc8dd2 100644 (file)
--- a/Data/Monoid.hs
+++ b/Data/Monoid.hs
@@ -2,7 +2,7 @@
 -- |
 -- 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
@@ -58,3 +58,33 @@ instance Monoid () where
        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