diff --git a/.gitignore b/.gitignore
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,13 @@
-_darcs
 dist
+docs
+wiki
+TAGS
+tags
+wip
+.DS_Store
+.*.swp
+.*.swo
+*.o
+*.hi
+*~
+*#
diff --git a/semigroupoids.cabal b/semigroupoids.cabal
--- a/semigroupoids.cabal
+++ b/semigroupoids.cabal
@@ -1,6 +1,6 @@
 name:          semigroupoids
 category:      Control, Comonads
-version:       3.0.3
+version:       3.1
 license:       BSD3
 cabal-version: >= 1.6
 license-file:  LICENSE
diff --git a/src/Data/Semigroupoid.hs b/src/Data/Semigroupoid.hs
--- a/src/Data/Semigroupoid.hs
+++ b/src/Data/Semigroupoid.hs
@@ -43,6 +43,10 @@
 instance Semigroupoid (->) where
   o = (.)
 
+-- | <http://en.wikipedia.org/wiki/Band_(mathematics)#Rectangular_bands>
+instance Semigroupoid (,) where
+  o (_,k) (i,_) = (i,k)
+
 instance Bind m => Semigroupoid (Kleisli m) where
   Kleisli g `o` Kleisli f = Kleisli $ \a -> f a >>- g