diff --git a/Data/Histogram.hs b/Data/Histogram.hs
--- a/Data/Histogram.hs
+++ b/Data/Histogram.hs
@@ -34,6 +34,7 @@
      -- * Modification
   , map
   , bmap
+  , mapData
   , zip
   , zipSafe
     -- ** Type conversion
@@ -128,6 +129,11 @@
 bmap :: (Unbox a, Unbox b, Bin bin)
      => (BinValue bin -> a -> b) -> Histogram bin a -> Histogram bin b
 bmap = H.bmap
+
+mapData :: (Unbox a, Unbox b, Bin bin)
+        => (Vector a -> Vector b) -> Histogram bin a -> Histogram bin b
+mapData = H.mapData
+
 
 zip :: (Bin bin, BinEq bin, Unbox a, Unbox b, Unbox c) 
     => (a -> b -> c) -> Histogram bin a -> Histogram bin b -> Histogram bin c
diff --git a/Data/Histogram/Bin/Bin2D.hs b/Data/Histogram/Bin/Bin2D.hs
--- a/Data/Histogram/Bin/Bin2D.hs
+++ b/Data/Histogram/Bin/Bin2D.hs
@@ -17,7 +17,7 @@
 import Text.Read       (Read(..))
 
 import Data.Histogram.Bin.Classes
-import Data.Histogram.Parse
+import Data.Histogram.Bin.Read
 
 -- | 2D bins. binX is binning along X axis and binY is one along Y
 --   axis. Data is stored in row-major order
@@ -93,4 +93,7 @@
     by <- readPrec
     return $ Bin2D bx by
 
-instance NFData (Bin2D bx by)
+instance (NFData bx, NFData by) => NFData (Bin2D bx by) where
+  rnf (Bin2D bx by) = rnf bx `seq`
+                      rnf by `seq`
+                      ()
diff --git a/Data/Histogram/Bin/BinEnum.hs b/Data/Histogram/Bin/BinEnum.hs
--- a/Data/Histogram/Bin/BinEnum.hs
+++ b/Data/Histogram/Bin/BinEnum.hs
@@ -14,7 +14,7 @@
 
 import Data.Histogram.Bin.Classes
 import Data.Histogram.Bin.BinI
-import Data.Histogram.Parse
+import Data.Histogram.Bin.Read
 
 -- | Bin for types which are instnaces of Enum type class. Value are
 --   converted to 'Int' using 'fromEnum' first and then binned.
diff --git a/Data/Histogram/Bin/BinF.hs b/Data/Histogram/Bin/BinF.hs
--- a/Data/Histogram/Bin/BinF.hs
+++ b/Data/Histogram/Bin/BinF.hs
@@ -23,7 +23,7 @@
 import Text.Read       (Read(..))
 
 import Data.Histogram.Bin.Classes
-import Data.Histogram.Parse
+import Data.Histogram.Bin.Read
 
 
 -- | Floaintg point bins with equal sizes.
@@ -35,7 +35,7 @@
 data BinF f = BinF !f                  -- Lower bound
                    !f                  -- Size of bin
                    {-# UNPACK #-} !Int -- Number of bins
-              deriving (Data,Typeable)
+              deriving (Data,Typeable,Eq)
 
 -- | Create bins.
 binF :: RealFrac f =>
@@ -131,7 +131,7 @@
 data BinD = BinD {-# UNPACK #-} !Double -- Lower bound
                  {-# UNPACK #-} !Double -- Size of bin
                  {-# UNPACK #-} !Int    -- Number of bins
-            deriving (Data,Typeable)
+            deriving (Data,Typeable,Eq)
 
 -- | Create bins.
 binD :: Double -- ^ Lower bound of range
diff --git a/Data/Histogram/Bin/BinI.hs b/Data/Histogram/Bin/BinI.hs
--- a/Data/Histogram/Bin/BinI.hs
+++ b/Data/Histogram/Bin/BinI.hs
@@ -13,7 +13,7 @@
 import Text.Read       (Read(..))
 
 import Data.Histogram.Bin.Classes
-import Data.Histogram.Parse
+import Data.Histogram.Bin.Read
 
 
 
diff --git a/Data/Histogram/Bin/BinInt.hs b/Data/Histogram/Bin/BinInt.hs
--- a/Data/Histogram/Bin/BinInt.hs
+++ b/Data/Histogram/Bin/BinInt.hs
@@ -14,7 +14,7 @@
 import Text.Read       (Read(..))
 
 import Data.Histogram.Bin.Classes
-import Data.Histogram.Parse
+import Data.Histogram.Bin.Read
 
 
 
diff --git a/Data/Histogram/Bin/Classes.hs b/Data/Histogram/Bin/Classes.hs
--- a/Data/Histogram/Bin/Classes.hs
+++ b/Data/Histogram/Bin/Classes.hs
@@ -116,8 +116,8 @@
       n = nBins b       
 
 -- | How index should be dropped
-data CutDirection = CutLower    -- ^ Drop bins with highest index
-                  | CutHigher   -- ^ Drop bins with lowest index
+data CutDirection = CutLower    -- ^ Drop bins with smallest index
+                  | CutHigher   -- ^ Drop bins with bigger index
 
 
 -- | Bin which support rebinning. 
diff --git a/Data/Histogram/Bin/Extra.hs b/Data/Histogram/Bin/Extra.hs
--- a/Data/Histogram/Bin/Extra.hs
+++ b/Data/Histogram/Bin/Extra.hs
@@ -32,7 +32,7 @@
 import Text.Read          (Read(..))         
 
 import Data.Histogram.Bin
-import Data.Histogram.Parse
+import Data.Histogram.Bin.Read
 
 ----------------------------------------------------------------
 
diff --git a/Data/Histogram/Bin/LogBinD.hs b/Data/Histogram/Bin/LogBinD.hs
--- a/Data/Histogram/Bin/LogBinD.hs
+++ b/Data/Histogram/Bin/LogBinD.hs
@@ -15,13 +15,13 @@
 import Text.Read       (Read(..))
 
 import Data.Histogram.Bin.Classes
-import Data.Histogram.Parse
+import Data.Histogram.Bin.Read
 
 
 
 -- | Uniform binning in logarithmic scale. For roundtripping use:
 --
--- > b = logBinDN (lowerBound b) (logBinDIncrement b) (nBins b)
+-- > b = logBinDN (lowerLimit b) (logBinDIncrement b) (nBins b)
 data LogBinD = LogBinD
                Double -- Low border
                Double -- Increment ratio
diff --git a/Data/Histogram/Bin/MaybeBin.hs b/Data/Histogram/Bin/MaybeBin.hs
new file mode 100644
--- /dev/null
+++ b/Data/Histogram/Bin/MaybeBin.hs
@@ -0,0 +1,40 @@
+{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+module Data.Histogram.Bin.MaybeBin (
+    MaybeBin(..)
+  ) where
+
+import Control.Monad   (liftM)
+import Data.Typeable   (Typeable)
+import Text.Read       (Read(..))
+
+import Data.Histogram.Bin.Classes
+import Data.Histogram.Bin.Read
+
+
+-- | This binning algorithms adds special case of no value.
+newtype MaybeBin bin = MaybeBin bin
+                       deriving (BinEq,Eq,Typeable)
+
+instance Bin bin => Bin (MaybeBin bin) where
+  type BinValue (MaybeBin bin) = Maybe (BinValue bin)
+  toIndex _            Nothing  = 0
+  toIndex (MaybeBin b) (Just x) = 1 + toIndex b x
+
+  fromIndex _            0 = Nothing
+  fromIndex (MaybeBin b) i = Just (fromIndex b (i-1))
+
+  nBins (MaybeBin b) = 1 + nBins b
+
+instance VariableBin bin => VariableBin (MaybeBin bin) where
+  binSizeN  _           0 = Nothing
+  binSizeN (MaybeBin b) n = Just $ binSizeN b (n-1)
+
+instance Show bin => Show (MaybeBin bin) where
+  show (MaybeBin bin) = "# MaybeBin\n" ++ show bin
+
+instance Read bin => Read (MaybeBin bin) where
+  readPrec = do
+    keyword "MaybeBin"
+    liftM MaybeBin readPrec
diff --git a/Data/Histogram/Bin/Read.hs b/Data/Histogram/Bin/Read.hs
new file mode 100644
--- /dev/null
+++ b/Data/Histogram/Bin/Read.hs
@@ -0,0 +1,45 @@
+-- | Helper function for defining Read instances for bin data types.
+module Data.Histogram.Bin.Read 
+  ( ws
+  , eol
+  , value
+  , maybeValue
+  , keyword
+  ) where
+
+import Text.Read
+import Text.ParserCombinators.ReadP    (ReadP, many, satisfy, char, string)
+
+-- | Whitespaces
+ws :: ReadP String
+ws = many $ satisfy (`elem` " \t")
+
+-- | End of line
+eol :: ReadP Char
+eol = char '\n'
+
+-- | Equal sign
+eq :: ReadP ()
+eq = ws >> char '=' >> return ()
+
+-- | Key value pair
+value :: Read a => String -> ReadPrec a
+value str = do lift $ key str >> eq
+               getVal
+
+-- | Return optional value
+maybeValue :: Read a => String -> ReadPrec (Maybe a)
+maybeValue str = do lift (key str >> eq)
+                    lift (ws >> eol >> return Nothing) <++ (Just `fmap` getVal)
+
+-- | Keyword
+keyword :: String -> ReadPrec ()
+keyword str = lift $ key str >> ws >> eol >> return ()
+
+
+key :: String -> ReadP String
+key s = char '#' >> ws >> string s 
+
+getVal :: Read a => ReadPrec a
+getVal = do x <- readPrec
+            lift eol >> return x
diff --git a/Data/Histogram/Generic.hs b/Data/Histogram/Generic.hs
--- a/Data/Histogram/Generic.hs
+++ b/Data/Histogram/Generic.hs
@@ -31,6 +31,7 @@
     -- * Modification
   , map
   , bmap
+  , mapData
   , zip
   , zipSafe
     -- ** Type conversion
@@ -71,7 +72,7 @@
 import qualified Prelude    (zip)
 
 import Data.Histogram.Bin
-import Data.Histogram.Parse
+import Data.Histogram.Bin.Read
 
 ----------------------------------------------------------------
 -- Data type and smart constructors
@@ -216,6 +217,13 @@
 bmap f (Histogram bin _ vec) =
   Histogram bin Nothing $ G.imap (f . fromIndex bin) vec
 
+mapData :: (Vector v a, Vector u b, Bin bin)
+        => (v a -> u b) -> Histogram v bin a -> Histogram u bin b
+mapData f (Histogram bin _ v)
+  | G.length v /= G.length v' = error "Data.Histogram.Generic.Histogram.mapData: vector length changed"
+  | otherwise                 = Histogram bin Nothing v'
+  where v' = f v
+
 -- | Zip two histograms elementwise. Bins of histograms must be equal
 --   otherwise error will be called.
 zip :: (Bin bin, BinEq bin, Vector v a, Vector v b, Vector v c) =>
@@ -270,7 +278,8 @@
 ----------------------------------------------------------------
 
 -- | Slice histogram. Values/indices specify inclusive
---   variant. Under/overflows are discarded.
+--   variant. Under/overflows are discarded. If requested value falls
+--   out of histogram range it will be truncated.
 slice :: (SliceableBin bin, Vector v a)
       => HistIndex bin          -- ^ Lower inclusive bound
       -> HistIndex bin          -- ^ Upper inclusive bound
@@ -279,8 +288,9 @@
 slice a b (Histogram bin _ v) =
   Histogram (sliceBin i j bin) Nothing (G.slice i (j - i + 1) v)
   where
-    i = histIndex bin a
-    j = histIndex bin b
+    i = max 0 $ histIndex bin a
+    j = min n $ histIndex bin b
+    n = nBins bin - 1
 
 -- | Rebin histogram by joining @n@ adjacent bins.
 rebin :: (MergeableBin bin, Vector v a)
diff --git a/Data/Histogram/Parse.hs b/Data/Histogram/Parse.hs
deleted file mode 100644
--- a/Data/Histogram/Parse.hs
+++ /dev/null
@@ -1,44 +0,0 @@
-module Data.Histogram.Parse ( ws
-                            , eol
-                            , value
-                            , maybeValue
-                            , keyword
-                            ) where
-
-import Text.Read
-import Text.ParserCombinators.ReadP    (ReadP, many, satisfy, char, string)
-
--- Whitespaces
-ws :: ReadP String
-ws = many $ satisfy (`elem` " \t")
-
--- End of line
-eol :: ReadP Char
-eol = char '\n'
-
--- Equal sign
-eq :: ReadP ()
-eq = ws >> char '=' >> return ()
-
--- Key
-key :: String -> ReadP String
-key s = char '#' >> ws >> string s 
-
-
-getVal :: Read a => ReadPrec a
-getVal = do x <- readPrec
-            lift eol >> return x
-
--- Key value pair
-value :: Read a => String -> ReadPrec a
-value str = do lift $ key str >> eq
-               getVal
-
--- Return optional value
-maybeValue :: Read a => String -> ReadPrec (Maybe a)
-maybeValue str = do lift (key str >> eq)
-                    lift (ws >> eol >> return Nothing) <++ (Just `fmap` getVal)
-
--- Keyword
-keyword :: String -> ReadPrec ()
-keyword str = lift $ key str >> ws >> eol >> return ()
diff --git a/LICENSE b/LICENSE
--- a/LICENSE
+++ b/LICENSE
@@ -0,0 +1,30 @@
+Copyright (c)2009-2012, Aleksey Khudyakov
+
+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 asd 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/histogram-fill.cabal b/histogram-fill.cabal
--- a/histogram-fill.cabal
+++ b/histogram-fill.cabal
@@ -1,10 +1,25 @@
 Name:           histogram-fill
-Version:        0.6.1.0
+Version:        0.6.2.0
 Synopsis:       Library for histograms creation.
 Description:    
   This is library for histograms filling. Its aim to provide
   convenient way to create and fill histograms. 
   .
+  Changes in 0.6.2.0
+  .
+  * MaybeBin added.
+  .
+  * Helper function for defining Read instances for bins are exposed. 
+  .
+  * mapData function is added.
+  .
+  * Slicing histogram do not results in crash if indices are out of
+    bounds.
+  .
+  * Eq instances for BinF and BinD are added.
+  .
+  * NFData instance for Bin2D is fixed.
+  .
   Changes in 0.6.1.0
   .
   * Helper function and type synonym for Bin2D
@@ -13,7 +28,7 @@
   .
   * Fixed compilation with GHC 7.4
 
-Cabal-Version:  >= 1.6
+Cabal-Version:  >= 1.8
 License:        BSD3
 License-File:   LICENSE
 Author:         Alexey Khudyakov
@@ -47,9 +62,23 @@
                         Data.Histogram.Bin.BinEnum
                         Data.Histogram.Bin.BinF
                         Data.Histogram.Bin.LogBinD
+                        Data.Histogram.Bin.MaybeBin
                         Data.Histogram.Bin.Bin2D
                         Data.Histogram.Bin.Extra
+                        Data.Histogram.Bin.Read
                         Data.Histogram.ST
-  Other-modules:        Data.Histogram.Parse
   Ghc-options:          -O2 -Wall
   Ghc-prof-options:     -auto-all
+
+test-suite tests
+  type:           exitcode-stdio-1.0
+  hs-source-dirs: test
+  main-is:        QC.hs
+  other-modules:  QC.Instances
+  ghc-options:    -Wall
+  build-depends:  base >=3 && < 5,
+                  histogram-fill,
+                  vector,
+                  QuickCheck >= 2,
+                  test-framework,
+                  test-framework-quickcheck2