diff --git a/Data/Histogram/Bin.hs b/Data/Histogram/Bin.hs
--- a/Data/Histogram/Bin.hs
+++ b/Data/Histogram/Bin.hs
@@ -144,8 +144,8 @@
 -- | Simple binning algorithm which map continous range of bins onto
 -- indices. Each number correcsponds to different bin
 data BinI = BinI
-            {-# UNPACK #-} !Int -- ^ Lower bound (inclusive)
-            {-# UNPACK #-} !Int -- ^ Upper bound (inclusive)
+            {-# UNPACK #-} !Int -- Lower bound (inclusive)
+            {-# UNPACK #-} !Int -- Upper bound (inclusive)
             deriving (Eq,Typeable)
 
 -- | Construct BinI with n bins. Indexing starts from 0
@@ -191,9 +191,9 @@
 
 -- | Integer bins with size which differ from 1.
 data BinInt = BinInt
-              {-# UNPACK #-} !Int -- ^ Low bound
-              {-# UNPACK #-} !Int -- ^ Bin size
-              {-# UNPACK #-} !Int -- ^ Number of bins
+              {-# UNPACK #-} !Int -- Low bound
+              {-# UNPACK #-} !Int -- Bin size
+              {-# UNPACK #-} !Int -- Number of bins
               deriving (Eq,Typeable)
 
 -- | Construct BinInt.
@@ -281,9 +281,9 @@
 --
 -- Note that due to GHC bug #2271 this toIndex is really slow (20x
 -- slowdown with respect to BinD) and use of BinD is recommended
-data BinF f = BinF {-# UNPACK #-} !f   -- ^ Lower bound
-                   {-# UNPACK #-} !f   -- ^ Size of bin
-                   {-# UNPACK #-} !Int -- ^ Number of bins
+data BinF f = BinF {-# UNPACK #-} !f   -- Lower bound
+                   {-# UNPACK #-} !f   -- Size of bin
+                   {-# UNPACK #-} !Int -- Number of bins
               deriving (Eq,Typeable)
 
 -- | Create bins.
@@ -355,9 +355,9 @@
 ----------------------------------------------------------------
 -- | Floaintg point bins with equal sizes. If you work with Doubles
 -- this data type should be used instead of BinF.
-data BinD = BinD {-# UNPACK #-} !Double -- ^ Lower bound
-                 {-# UNPACK #-} !Double -- ^ Size of bin
-                 {-# UNPACK #-} !Int    -- ^ Number of bins
+data BinD = BinD {-# UNPACK #-} !Double -- Lower bound
+                 {-# UNPACK #-} !Double -- Size of bin
+                 {-# UNPACK #-} !Int    -- Number of bins
             deriving (Eq,Typeable)
 
 -- | Create bins.
@@ -433,10 +433,10 @@
 ----------------------------------------------------------------
 -- | Logarithmic scale bins.
 data LogBinD = LogBinD
-               Double -- ^ Low border
-               Double -- ^ Hi border
-               Double -- ^ Increment ratio
-               Int    -- ^ Number of bins
+               Double -- Low border
+               Double -- Hi border
+               Double -- Increment ratio
+               Int    -- Number of bins
                deriving (Eq,Typeable)
 
 -- | Create log-scale bins.
diff --git a/Data/Histogram/Fill.hs b/Data/Histogram/Fill.hs
--- a/Data/Histogram/Fill.hs
+++ b/Data/Histogram/Fill.hs
@@ -27,6 +27,8 @@
                            , treeHBuilderMonoidM
                              -- ** Stateless
                            , HBuilder
+                           , toHBuilderST
+                           , toHBuilderIO
                            , joinHBuilder
                            , joinHBuilderMonoid
                            , treeHBuilder
@@ -49,8 +51,9 @@
 import Control.Monad.ST 
 import Control.Monad.Primitive
 
-import Data.Monoid         (Monoid(..))
-import Data.Vector.Unboxed (Unbox)
+import Data.Monoid            (Monoid(..))
+-- import Data.Monoid.Statistics (StatMonoid)
+import Data.Vector.Unboxed    (Unbox)
 
 import Data.Histogram
 import Data.Histogram.Bin
@@ -176,8 +179,19 @@
 ----------------------------------------------------------------
 
 -- | Stateless histogram builder
-newtype HBuilder a b = HBuilder { toBuilderM :: (forall s . ST s (HBuilderM (ST s) a b)) }
+newtype HBuilder a b = HBuilder { toHBuilderST :: (forall s . ST s (HBuilderM (ST s) a b)) 
+                                  -- ^ Convert builder to stateful builder in 'ST' monad
+                                }
 
+-- | Convert builder to builder in IO monad
+toHBuilderIO :: HBuilder a b -> IO (HBuilderM IO a b)
+toHBuilderIO (HBuilder h) = do 
+  builder <- stToIO h
+  return (HBuilderM 
+          (stToIO . hbInput builder) 
+          (stToIO $ hbOutput builder))
+{-# INLINE toHBuilderIO #-}
+  
 instance HistBuilder (HBuilder) where
     modifyIn  f (HBuilder h) = HBuilder (modifyIn  f <$> h)
     addCut    f (HBuilder h) = HBuilder (addCut    f <$> h)
@@ -192,7 +206,7 @@
 
 -- | Join list of builders
 joinHBuilder :: [HBuilder a b] -> HBuilder a [b]
-joinHBuilder hs = HBuilder (joinHBuilderM <$> mapM toBuilderM hs)
+joinHBuilder hs = HBuilder (joinHBuilderM <$> mapM toHBuilderST hs)
 {-# INLINE joinHBuilder #-}
 
 -- | Join list of builders
@@ -238,13 +252,21 @@
                                                   }
 {-# INLINE mkMonoidal #-}
 
+-- mkMonoidalAcc :: (Bin bin, Unbox val, StatMonoid val a
+--                  ) => bin -> HBuilder (BinValue bin,a) (Histogram bin val)
+-- mkMonoidalAcc bin = HBuilder $ do acc <- newMHistogram mempty bin
+--                                   return $ HBuilderM { hbInput  = fillMonoidAccum acc
+--                                                      , hbOutput = freezeHist acc
+--                                                      }
+-- {-# INLINE mkMonoidalAcc #-}
+
 ----------------------------------------------------------------
 -- Actual filling of histograms
 ----------------------------------------------------------------
 
 fillBuilder :: HBuilder a b -> [a] -> b
 fillBuilder hb xs = 
-    runST $ do h <- toBuilderM hb
+    runST $ do h <- toHBuilderST hb
                mapM_ (feedOne h) xs
                freezeHBuilderM h
 
diff --git a/Data/Histogram/Generic.hs b/Data/Histogram/Generic.hs
--- a/Data/Histogram/Generic.hs
+++ b/Data/Histogram/Generic.hs
@@ -192,7 +192,7 @@
     where
       (nx, ny) = nBins2D b
       mkSlice i = ( fromIndex (binY b) i
-                  , Histogram (binX b) Nothing (G.slice nx (nx*i) a) )
+                  , Histogram (binX b) Nothing (G.slice (nx*i) nx a) )
 
 -- | Slice 2D histogram along X axis.
 sliceX :: (Vector v a, Bin bX, Bin bY) => Histogram v (Bin2D bX bY) a -> [(BinValue bX, Histogram v bY a)]
diff --git a/Data/Histogram/ST.hs b/Data/Histogram/ST.hs
--- a/Data/Histogram/ST.hs
+++ b/Data/Histogram/ST.hs
@@ -14,6 +14,7 @@
                          , fillOne
                          , fillOneW
                          , fillMonoid
+                         -- , fillMonoidAccum
                          , unsafeFreezeHist
                          , freezeHist
                          ) where
@@ -21,6 +22,7 @@
 import Control.Monad.Primitive
 
 import Data.Monoid
+-- import Data.Monoid.Statistics
 import qualified Data.Vector.Unboxed as U
 import qualified Data.Vector.Unboxed.Mutable as MU
 import qualified Data.Vector.Generic as G
@@ -73,7 +75,17 @@
       i = toIndex bin x
 {-# INLINE fillMonoid #-}
 
-
+-- -- | Add one element to monoidal accumulator
+-- fillMonoidAccum :: (PrimMonad m, StatMonoid val a, U.Unbox val, Bin bin) 
+--                 => MHistogram (PrimState m) bin val -> (BinValue bin, a) -> m ()
+-- fillMonoidAccum (MHistogram bin uo arr) !(x,a)
+--     | i < 0              = MU.unsafeWrite uo  0 . pappend a =<< MU.unsafeRead uo  0
+--     | i >= MU.length arr = MU.unsafeWrite uo  1 . pappend a =<< MU.unsafeRead uo  1
+--     | otherwise          = MU.unsafeWrite arr i . pappend a =<< MU.unsafeRead arr i
+--     where 
+--       i = toIndex bin x
+-- {-# INLINE fillMonoidAccum #-}
+    
 -- | Create immutable histogram from mutable one. This operation is
 -- unsafe! Accumulator mustn't be used after that
 unsafeFreezeHist :: (PrimMonad m, U.Unbox a, Bin bin) => MHistogram (PrimState m) bin a -> m (Histogram bin a)
diff --git a/histogram-fill.cabal b/histogram-fill.cabal
--- a/histogram-fill.cabal
+++ b/histogram-fill.cabal
@@ -1,5 +1,5 @@
 Name:           histogram-fill
-Version:        0.3.0.1
+Version:        0.3.1
 Cabal-Version:  >= 1.6
 License:        BSD3
 License-File:   LICENSE
@@ -18,7 +18,10 @@
   location: http://bitbucket.org/Shimuuar/histogram-fill
 
 Library
-  Build-Depends:        base >=3 && <5, primitive, vector
+  Build-Depends:        base >=3 && <5,
+                        primitive,
+                        vector >= 0.6.0.2
+--                        monoid-statistics == 0.1.*
   Exposed-modules:      Data.Histogram
                         Data.Histogram.Generic
                         Data.Histogram.Fill