diff --git a/example/Domino.hs b/example/Domino.hs
--- a/example/Domino.hs
+++ b/example/Domino.hs
@@ -38,6 +38,7 @@
 import Control.Applicative (pure)
 import Data.Set (Set)
 import Data.Monoid (Monoid, mempty, mappend, mconcat)
+import Data.Semigroup (Semigroup, (<>))
 
 
 data
@@ -57,13 +58,16 @@
 
 type Assign = ESC.Assign Borders (Set X)
 
-instance Monoid Borders where
-   mempty = Borders mempty mempty
-   mappend x y =
+instance Semigroup Borders where
+   x <> y =
       Borders {
          vertical = Set.union (vertical x) (vertical y),
          horizontal = Set.union (horizontal x) (horizontal y)
       }
+
+instance Monoid Borders where
+   mempty = Borders mempty mempty
+   mappend = (<>)
 
 
 above, left :: Position -> Position
diff --git a/set-cover.cabal b/set-cover.cabal
--- a/set-cover.cabal
+++ b/set-cover.cabal
@@ -1,5 +1,5 @@
 Name:             set-cover
-Version:          0.0.8
+Version:          0.0.9
 License:          BSD3
 License-File:     LICENSE
 Author:           Henning Thielemann, Helmut Podhaisky
@@ -32,7 +32,7 @@
   default:     False
 
 Source-Repository this
-  Tag:         0.0.8
+  Tag:         0.0.9
   Type:        darcs
   Location:    http://hub.darcs.net/thielema/set-cover/
 
@@ -45,6 +45,7 @@
     psqueues >=0.2 && <0.3,
     enummapset >=0.1 && <0.6,
     containers >=0.4 && <0.6,
+    semigroups >=0.1 && <1.0,
     utility-ht >=0.0.12 && <0.1,
     base >=4 && <5
 
@@ -193,6 +194,7 @@
       set-cover,
       unicode >=0.0 && <0.1,
       containers,
+      semigroups,
       utility-ht,
       base
   Else
diff --git a/src/Math/SetCover/BitMap.hs b/src/Math/SetCover/BitMap.hs
--- a/src/Math/SetCover/BitMap.hs
+++ b/src/Math/SetCover/BitMap.hs
@@ -15,12 +15,16 @@
 
 import qualified Data.List.Reverse.StrictSpine as ListRev
 import Data.Monoid (Monoid, mempty, mappend)
+import Data.Semigroup (Semigroup, (<>))
 
 
 {-
 Sliced representation of Map [0..bitSize-1] Integer.
 -}
 newtype Map bits = Map {unMap :: [bits]} deriving (Show)
+
+instance (Bit.C bits) => Semigroup (Map bits) where
+   (<>) = add
 
 instance (Bit.C bits) => Monoid (Map bits) where
    mempty = Map []
diff --git a/src/Math/SetCover/BitSet.hs b/src/Math/SetCover/BitSet.hs
--- a/src/Math/SetCover/BitSet.hs
+++ b/src/Math/SetCover/BitSet.hs
@@ -4,13 +4,17 @@
 import Math.SetCover.Bit ((.|.), (.&.))
 
 import Data.Monoid (Monoid, mempty, mappend)
+import Data.Semigroup (Semigroup, (<>))
 
 
 newtype Set bits = Set bits deriving (Eq, Ord, Show)
 
+instance (Bit.C bits) => Semigroup (Set bits) where
+   Set x <> Set y = Set $ x.|.y
+
 instance (Bit.C bits) => Monoid (Set bits) where
    mempty = empty
-   mappend (Set x) (Set y) = Set $ x.|.y
+   mappend = (<>)
 
 empty :: Bit.C bits => Set bits
 empty = Set Bit.empty