Monoid instance for UniqSet

gergoerdi · Jan 7, 2014 · afefa7a · afefa7a
1 parent 4d70840
commit afefa7a
Showing 1 changed file with 14 additions and 0 deletions.
diff --git a/compiler/utils/UniqSet.lhs b/compiler/utils/UniqSet.lhs
@@ -36,6 +36,7 @@ module UniqSet (
 
 import UniqFM
 import Unique
+import Data.Monoid
 
 \end{code}
 
@@ -75,6 +76,19 @@ isEmptyUniqSet :: UniqSet a -> Bool
 lookupUniqSet :: Uniquable a => UniqSet a -> a -> Maybe a
 uniqSetToList :: UniqSet a -> [a]
 \end{code}
+
+%************************************************************************
+%*                                                                      *
+\subsection{Monoid interface}
+%*                                                                      *
+%************************************************************************
+
+\begin{code}
+instance Monoid (UniqSet a) where
+    mempty = emptyUniqSet
+    mappend = unionUniqSets
+\end{code}
+
 %************************************************************************
 %*                                                                      *
 \subsection{Implementation using ``UniqFM''}