diff --git a/Algebra.hs b/Algebra.hs
--- a/Algebra.hs
+++ b/Algebra.hs
@@ -99,6 +99,9 @@
 instance Group (Sum Int) where invert (Sum a) = Sum (Base.negate a)
 instance Group (Sum Word) where invert (Sum a) = Sum (Base.negate a)
 
+infixl 6 +, -
+infixl 7 *, /
+
 (+) :: Semigroup (Sum a) => a -> a -> a
 a + b = getSum (Sum a <> Sum b)
 
diff --git a/alg.cabal b/alg.cabal
--- a/alg.cabal
+++ b/alg.cabal
@@ -1,5 +1,5 @@
 name:                alg
-version:             0.2.9.0
+version:             0.2.10.0
 synopsis:            Algebraic structures
 -- description:         
 license:             BSD3