diff --git a/LICENSE b/LICENSE
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--- /dev/null
+++ b/LICENSE
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+Copyright (c) 2015, Athan Clark
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of Athan Clark nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/Setup.hs b/Setup.hs
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+++ b/Setup.hs
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+import Distribution.Simple
+main = defaultMain
diff --git a/commutative.cabal b/commutative.cabal
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+++ b/commutative.cabal
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+Name:                   commutative
+Version:                0.0.1
+Author:                 Athan Clark <athan.clark@gmail.com>
+Maintainer:             Athan Clark <athan.clark@gmail.com>
+License:                BSD3
+License-File:           LICENSE
+Synopsis:               Commutative binary operations.
+Description:
+  This package provides a trivial class for abelian binary operations, and an
+  analogue to @Data.Foldable@.
+Cabal-Version:          >= 1.10
+Build-Type:             Simple
+Category:               Data, Math
+
+Library
+  Default-Language:     Haskell2010
+  HS-Source-Dirs:       src
+  GHC-Options:          -Wall
+  Exposed-Modules:      Data.Commutative
+                        Data.Mergeable
+  Build-Depends:        base >= 4.6 && < 5
+                      , random
+                      , semigroups
+
+Test-Suite spec
+  Type:                 exitcode-stdio-1.0
+  Default-Language:     Haskell2010
+  Hs-Source-Dirs:       src
+                      , test
+  Ghc-Options:          -Wall
+  Main-Is:              Spec.hs
+  Build-Depends:        base
+                      , tasty
+                      , tasty-quickcheck
+                      , tasty-hunit
+                      , QuickCheck
+                      , quickcheck-instances
+
+Source-Repository head
+  Type:                 git
+  Location:             https://github.com/athanclark/commutative.git
diff --git a/src/Data/Commutative.hs b/src/Data/Commutative.hs
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+++ b/src/Data/Commutative.hs
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+{-# LANGUAGE
+    GeneralizedNewtypeDeriving
+  #-}
+
+module Data.Commutative where
+
+import Data.Monoid (Any (..), All (..), First (..), Last (..), Sum (..), Product (..))
+import System.IO.Unsafe (unsafePerformIO)
+import System.Random (randomIO)
+
+
+class Commutative a where
+  commute :: a -> a -> a -- ^ Abelian magma - @x `commute` y == y `commute` x@.
+                         -- Note that the commutative behaviour should be embedded in the
+                         -- instance. For distinguished commutes, more information is needed - like
+                         -- a predicate as is the case for @commuteVia@ and @commuteViaM@.
+
+(<~>) :: Commutative a => a -> a -> a
+(<~>) = commute
+
+class Commutative a => CommutativeId a where
+  cempty :: a -- ^ Identity element - @x `commute` cempty == cempty `commute` x == x@
+
+-- | @flip@ when @False@ - simple & pure "predicative" commute.
+commuteVia :: Bool -> (a -> a -> a) -> a -> a -> a
+commuteVia p f = if p then f else flip f
+
+-- | Lifted predicative behaviour.
+commuteViaF :: Functor f => f Bool -> (a -> a -> a) -> a -> a -> f a
+commuteViaF mb f x y = (\b -> if b then f x y else f y x) <$> mb
+
+
+-- Unit
+instance Commutative () where
+  commute () () = ()
+
+instance CommutativeId () where
+  cempty = ()
+
+-- | Endomorphisms commutative over composition.
+-- __Warning__: The @Commutative@ instance uses @unsafePerformIO@ to randomly pick the order.
+newtype CommEndo a = CommEndo {appCommEndo :: a -> a}
+
+instance Commutative (CommEndo a) where
+  commute (CommEndo f) (CommEndo g) = CommEndo $ pick1 (f . g) (g . f) -- it doesn't matter which is chosen
+
+instance CommutativeId (CommEndo a) where
+  cempty = CommEndo id
+
+-- Booleans
+instance Commutative Any where
+  commute (Any x) (Any y) = Any $ x || y
+
+instance CommutativeId Any where
+  cempty = Any False
+
+instance Commutative All where
+  commute (All x) (All y) = All $ x && y
+
+instance CommutativeId All where
+  cempty = All True
+
+-- Maybe
+
+-- | In the case of two @Just@ values, the commutative instance randomly chooses one of them.
+-- __Warning__: The @Commutative@ instance uses @unsafePerformIO@ to randomly pick the order.
+newtype OneOf a = OneOf {getOneOf :: Maybe a}
+  deriving (Show, Eq)
+
+instance Commutative (OneOf a) where
+  commute (OneOf x) (OneOf y) = OneOf $ pick1 (getFirst $ First x `mappend` First y)
+                                              (getLast  $ Last x  `mappend` Last y)
+
+-- Numbers
+instance Num a => Commutative (Sum a) where
+  commute (Sum x) (Sum y) = Sum $ x + y
+
+instance Num a => CommutativeId (Sum a) where
+  cempty = Sum 0
+
+instance Num a => Commutative (Product a) where
+  commute (Product x) (Product y) = Product $ x * y
+
+instance Num a => CommutativeId (Product a) where
+  cempty = Product 1
+
+
+pick1 :: a -> a -> a
+pick1 l r = let leftOrRight = unsafePerformIO randomIO
+            in if leftOrRight then l else r
diff --git a/src/Data/Mergeable.hs b/src/Data/Mergeable.hs
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+++ b/src/Data/Mergeable.hs
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+{-# LANGUAGE
+    FlexibleInstances
+  , UndecidableInstances
+  #-}
+
+module Data.Mergeable where
+
+import Data.Commutative
+import Data.List.NonEmpty as NE
+
+
+class Mergeable t where
+  mergeMap :: CommutativeId m => (a -> m) -> t a -> m
+  merge :: (a -> b -> b) -> b -> t a -> b
+
+  mergeMap f = merge (commute . f) cempty
+  merge f i xs = appCommEndo (mergeMap (CommEndo . f) xs) i
+
+instance Mergeable [] where
+  mergeMap _ [] = cempty
+  mergeMap f (x:xs) = f x <~> mergeMap f xs
+
+
+class Functor t => Mergeable1 t where
+  mergeMap1 :: Commutative m => (a -> m) -> t a -> m
+  merge1 :: Commutative m => t m -> m
+
+  mergeMap1 f = merge1 . fmap f
+  merge1 = mergeMap1 id
+
+instance Mergeable1 NonEmpty where
+  mergeMap1 f (x:|[]) = f x
+  mergeMap1 f (x:|xs) = f x <~> mergeMap1 f (NE.fromList xs)
diff --git a/test/Spec.hs b/test/Spec.hs
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+module Spec where
+
+import Data.CommutativeSpec
+
+import Test.Tasty
+
+
+main :: IO ()
+main = defaultMain tests
+
+tests :: TestTree
+tests = testGroup "Testing..."
+  [spec]