diff --git a/Control/Monad/Atom.hs b/Control/Monad/Atom.hs
new file mode 100644
--- /dev/null
+++ b/Control/Monad/Atom.hs
@@ -0,0 +1,101 @@
+{-# LANGUAGE  GeneralizedNewtypeDeriving 
+  , NoMonomorphismRestriction 
+  , BangPatterns #-}
+module Control.Monad.Atom
+    ( MonadAtom (..)
+    , AtomTable
+    , Atom
+    , AtomT
+    , empty
+    , evalAtom
+    , evalAtomT
+    , runAtom
+    , runAtomT
+    )
+where
+import Control.Monad.State
+import Control.Monad.Identity
+import qualified Data.Map as Map
+import qualified Data.IntMap as IntMap
+import qualified Data.Binary as B
+import qualified Data.ByteString.Lazy as BS
+
+type Blob = BS.ByteString
+
+data AtomTable = T { lastID :: {-# UNPACK #-} !Int 
+                   , to     :: Map.Map Blob Int 
+                   , from   :: IntMap.IntMap Blob } 
+                   deriving (Eq,Show)
+
+
+instance B.Binary AtomTable where
+    put t = do B.put (lastID t) 
+               B.put (to t)
+               B.put (from t)
+    get = do liftM3 T B.get B.get B.get
+
+
+class Monad m => MonadAtom m where
+    -- | Monadically convert the argument into an atom (represented as an Int)
+    toAtom      :: B.Binary a => a -> m Int
+    -- | Monadically convert the argument into an atom, but only if 
+    -- the corresponding atom has already been created
+    maybeToAtom :: B.Binary a => a -> m (Maybe Int)
+    -- | Monadically convert an atom represented as an Int to its 
+    -- corresponding object
+    fromAtom    :: B.Binary a => Int -> m a
+
+
+instance Monad m => MonadAtom (AtomT m) where
+    toAtom x = AtomT $ do
+      let b = B.encode x
+      t <- get
+      case Map.lookup b (to t) of
+        Just j -> return $! j
+        Nothing -> do 
+                 let i = lastID t
+                     i' = i + 1 
+                     !t' = t { lastID = i'
+                             , to = Map.insert b  i (to t) 
+                             , from = IntMap.insert i b (from t) }
+                 put t'
+                 return $! lastID t
+
+    maybeToAtom x = 
+        AtomT $ do
+          t <- get
+          return . Map.lookup (B.encode x) . to $ t
+            
+    fromAtom i = AtomT $ do
+      t <- get
+      return . B.decode $ (from t) IntMap.! i
+
+table = AtomT get
+
+empty :: AtomTable
+empty = T 0 Map.empty IntMap.empty
+
+runAtomT :: AtomT t t1 -> AtomTable -> t (t1, AtomTable)
+runAtomT (AtomT x) s = runStateT x s
+
+runAtom :: Atom t -> AtomTable -> (t, AtomTable)
+runAtom (Atom x) s = runIdentity (runAtomT x s)
+
+
+evalAtom :: Atom t -> t
+evalAtom = fst . flip runAtom empty
+
+evalAtomT :: (Monad m) => AtomT m a -> m a
+evalAtomT = liftM fst . flip runAtomT empty
+
+newtype AtomT m r = AtomT (StateT AtomTable m r)
+    deriving (Functor,Monad,MonadTrans,MonadIO)
+
+newtype Atom r = Atom (AtomT Identity r)
+    deriving (Functor,Monad,MonadAtom)
+
+example :: [String]
+example = evalAtom $ do 
+  xs <- mapM toAtom . map show $ [1,2,3,1,2,3]
+  zs <- mapM fromAtom xs 
+  return zs
diff --git a/LICENSE b/LICENSE
new file mode 100644
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,30 @@
+Copyright (c)2011, Grzegorz Chrupała
+
+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 Grzegorz Chrupała 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
new file mode 100644
--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/monad-atom.cabal b/monad-atom.cabal
new file mode 100644
--- /dev/null
+++ b/monad-atom.cabal
@@ -0,0 +1,59 @@
+-- monad-atom.cabal auto-generated by cabal init. For additional
+-- options, see
+-- http://www.haskell.org/cabal/release/cabal-latest/doc/users-guide/authors.html#pkg-descr.
+-- The name of the package.
+Name:                monad-atom
+
+-- The package version. See the Haskell package versioning policy
+-- (http://www.haskell.org/haskellwiki/Package_versioning_policy) for
+-- standards guiding when and how versions should be incremented.
+Version:             0.1.0
+
+-- A short (one-line) description of the package.
+Synopsis:            Monadically convert objects to unique atoms and back.
+
+-- A longer description of the package.
+Description:         Monadically convert objects to unique atoms and back.
+
+-- The license under which the package is released.
+License:             BSD3
+
+-- The file containing the license text.
+License-file:        LICENSE
+
+-- The package author(s).
+Author:              Grzegorz Chrupała
+
+-- An email address to which users can send suggestions, bug reports,
+-- and patches.
+Maintainer:          gchrupala@lsv.uni-saarland.de
+
+-- A copyright notice.
+-- Copyright:           
+
+Category:            Control
+
+Build-type:          Simple
+
+-- Extra files to be distributed with the package, such as examples or
+-- a README.
+-- Extra-source-files:  
+
+-- Constraint on the version of Cabal needed to build this package.
+Cabal-version:       >=1.2
+
+
+Library
+  -- Modules exported by the library.
+  Exposed-modules:     Control.Monad.Atom
+  
+  -- Packages needed in order to build this package.
+  Build-depends: base >= 3 && < 5, bytestring >= 0.9, binary >= 0.5,
+                 containers >= 0.4, mtl >= 2.0
+
+  -- Modules not exported by this package.
+  -- Other-modules:       
+  
+  -- Extra tools (e.g. alex, hsc2hs, ...) needed to build the source.
+  -- Build-tools:         
+