From: Ross Paterson <ross@soi.city.ac.uk>
Date: Fri, 2 Feb 2007 19:08:47 +0000 (+0000)
Subject: add derived instances for Dual monoid
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=b5f74091bf655513e539c4048d789da89dd27ca7;p=ghc-base.git

add derived instances for Dual monoid
---

diff --git a/Data/Monoid.hs b/Data/Monoid.hs
index 8a30b73..c51c4ca 100644
--- a/Data/Monoid.hs
+++ b/Data/Monoid.hs
@@ -97,6 +97,7 @@ instance Monoid Ordering where
 
 -- | The dual of a monoid, obtained by swapping the arguments of 'mappend'.
 newtype Dual a = Dual { getDual :: a }
+	deriving (Eq, Ord, Read, Show, Bounded)
 
 instance Monoid a => Monoid (Dual a) where
 	mempty = Dual mempty