diff --git a/LICENSE b/LICENSE
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--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,30 @@
+Copyright Marco Zocca (c) 2018
+
+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 Marco Zocca 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/README.md b/README.md
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+++ b/README.md
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+# mwc-probability-transition
+
+[![Build Status](https://travis-ci.org/ocramz/mwc-probability-transition.png)](https://travis-ci.org/ocramz/mwc-probability-transition)
+
+Types and primitives for stochastic simulation (e.g. integration of SDE, random walks, Markov Chain Monte Carlo algorithms etc.)
diff --git a/Setup.hs b/Setup.hs
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+++ b/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/mwc-probability-transition.cabal b/mwc-probability-transition.cabal
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+++ b/mwc-probability-transition.cabal
@@ -0,0 +1,49 @@
+name:                mwc-probability-transition
+version:             0.1.0.0
+synopsis:            A Markov stochastic transition operator with logging
+description:
+            .
+            This package provides a 'Transition' type that is useful for modelling (and debugging) stochastic transition kernels (used in e.g. the integration of SDEs, Markov chain Monte Carlo algorithms etc.).
+            .
+            It wraps the compositional random sampling functionality of `mwc-probability` and offers structured logging via `logging-effect`.
+homepage:            https://github.com/ocramz/mwc-probability-transition
+license:             BSD3
+license-file:        LICENSE
+author:              Marco Zocca
+maintainer:          zocca.marco gmail
+copyright:           2018 Marco Zocca
+category:            Numeric
+build-type:          Simple
+extra-source-files:  README.md
+cabal-version:       >=1.10
+tested-with:         GHC == 8.2.2
+
+library
+  default-language:    Haskell2010
+  ghc-options:         -Wall
+  hs-source-dirs:      src
+  exposed-modules:     System.Random.MWC.Probability.Transition
+  build-depends:       base >= 4.7 && < 5
+                     , ghc-prim
+                     , logging-effect
+                     , mtl
+                     , mwc-probability
+                     , primitive
+                     , transformers
+
+
+
+test-suite spec
+  default-language:    Haskell2010
+  ghc-options:         -Wall
+  type:                exitcode-stdio-1.0
+  hs-source-dirs:      test
+  main-is:             LibSpec.hs
+  build-depends:       base
+                     , mwc-probability-transition
+                     , hspec
+                     , QuickCheck
+
+source-repository head
+  type:     git
+  location: https://github.com/ocramz/mwc-probability-transition
diff --git a/src/System/Random/MWC/Probability/Transition.hs b/src/System/Random/MWC/Probability/Transition.hs
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--- /dev/null
+++ b/src/System/Random/MWC/Probability/Transition.hs
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+{-# language OverloadedStrings #-}
+{-# language DeriveFunctor, GeneralizedNewtypeDeriving #-}
+module System.Random.MWC.Probability.Transition (
+  -- * Transition
+    Transition
+  , mkTransition
+  , runTransition
+  -- ** Helper functions
+  , withSeverity
+  -- * Re-exported from `logging-effect`
+  , Handler
+  , WithSeverity(..), Severity(..)
+  -- , withFDHandler, defaultBatchingOptions
+  ) where
+
+import Control.Monad
+import Control.Monad.Primitive
+
+import qualified Control.Monad.State as S
+
+import Control.Monad.Trans.Class (MonadTrans(..), lift)
+import Control.Monad.Trans.State.Strict (StateT(..), evalStateT, execStateT, runStateT)
+import Control.Monad.Log (MonadLog(..), Handler, WithSeverity(..), Severity(..), LoggingT(..), runLoggingT, withFDHandler, defaultBatchingOptions, logMessage)
+
+import Data.Char
+
+import System.Random.MWC.Probability
+
+
+
+-- | A Markov transition kernel.
+newtype Transition message s m a = Transition (
+  Gen (PrimState m) -> StateT s (LoggingT message m) a
+  ) deriving (Functor)
+
+-- | Construct a 'Transition' from sampling, state transformation and logging functions.
+--
+-- NB: The three function arguments are used in the order in which they appear here:
+--
+-- 1. a random sample @w :: t@ is produced, using the current state @x :: s@ as input
+--
+-- 2. output @z :: a@ and next state @x' :: s@ are computed using @w@ and @x@
+--
+-- 3. a logging message is constructed, using @z@ and @x'@ as arguments.
+mkTransition :: Monad m =>
+        (s -> Prob m t)     -- ^ Random generation
+     -> (s -> t -> (a, s))  -- ^ (Output, Next state)
+     -> (a -> s -> message) -- ^ Log message generation
+     -> Transition message s m a
+mkTransition fm fs flog = Transition $ \gen -> do
+  s <- S.get
+  w <- lift . lift $ sample (fm s) gen
+  let (a, s') = fs s w
+  lift $ logMessage $ flog a s' 
+  S.put s'
+  return a
+
+-- | Run a 'Transition' for a number of steps, while logging each iteration.
+runTransition :: Monad m =>
+         Handler m message        -- ^ Logging handler
+      -> Transition message s m a
+      -> Int                      -- ^ Number of iterations 
+      -> s                        -- ^ Initial state
+      -> Gen (PrimState m)        -- ^ PRNG
+      -> m [(a, s)]
+runTransition logf (Transition fm) n s0 g =
+  runLoggingT (replicateM n (runStateT (fm g) s0)) logf
+
+
+
+  
+bracketsUpp :: Show a => a -> String
+bracketsUpp p = unwords ["[", map toUpper (show p), "]"]
+
+-- | Render a logging message along with an annotation of its severity.
+withSeverity :: (t -> String) -> WithSeverity t -> String
+withSeverity k (WithSeverity u a ) = unwords [bracketsUpp u, k a]
+
+
diff --git a/test/LibSpec.hs b/test/LibSpec.hs
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--- /dev/null
+++ b/test/LibSpec.hs
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+module Main where
+
+import Test.Hspec
+import Test.Hspec.QuickCheck
+
+
+main :: IO ()
+main = hspec spec
+
+spec :: Spec
+spec =
+  describe "Lib" $ do
+    it "works" $ do
+      True `shouldBe` True
+    -- prop "ourAdd is commutative" $ \x y ->
+    --   ourAdd x y `shouldBe` ourAdd y x