diff --git a/LICENSE b/LICENSE
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--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,20 @@
+Copyright (c) 2014 Wei En
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be included
+in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
diff --git a/Setup.hs b/Setup.hs
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--- /dev/null
+++ b/Setup.hs
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+import Distribution.Simple
+main = defaultMain
diff --git a/counter.cabal b/counter.cabal
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--- /dev/null
+++ b/counter.cabal
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+name:          counter
+version:       0.1.0.0
+synopsis:      An object frequency counter.
+description:   This project provides an efficient object frequency counter, based upon Data.Map.Strict.
+homepage:      https://github.com/wei2912/counter
+
+license:       MIT
+license-file:  LICENSE
+
+author:        Wei En
+maintainer:    wei2912.supp0rt@gmail.com
+
+category:      Data
+build-type:    Simple
+
+cabal-version: >=1.10
+
+library
+  exposed-modules:   Data.Counter
+  build-depends:     base >=4.7 && <4.8,
+                     containers >=0.5 && <0.6
+  hs-source-dirs:    src 
+  default-language:  Haskell2010
diff --git a/src/Data/Counter.hs b/src/Data/Counter.hs
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--- /dev/null
+++ b/src/Data/Counter.hs
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+module Data.Counter where
+
+import qualified Data.Map.Strict as M
+import qualified Data.List as L
+
+{-|
+  The Counter type is an alias
+  of Data.Map.Strict.Map.
+-}
+type Counter k v = M.Map k v
+
+{-|
+  Initialize a counter with no keys.
+-}
+empty :: Counter k v
+empty = M.empty
+
+{-|
+  Initialize a counter with a single
+  instance of a key.
+-}
+singleton ::
+	Num v
+    => k -- ^ Key to be inserted.
+    -> Counter k v -- ^ New counter.
+singleton k = M.singleton k 1
+
+{-|
+  Increment the frequency count of a key
+  with a specified value.
+-}
+updateWith ::
+	(Ord k, Num v)
+	=> k -- ^ Key to be inserted.
+	-> v -- ^ Specified frequency count.
+	-> Counter k v -- ^ Old counter.
+	-> Counter k v -- ^ New counter.
+updateWith = M.insertWith (+)
+
+{-|
+  Increment the frequency count of a key by 1.
+-}
+update ::
+	(Ord k, Num v)
+	=> k -- ^ Key to be inserted.
+	-> Counter k v -- ^ Old counter.
+	-> Counter k v -- ^ New counter.
+update k = updateWith k 1
+
+{-|
+  Convert a list of items into a counter.
+-}
+count ::
+	(Ord k, Num v)
+	=> [k] -- ^ List of keys.
+	-> Counter k v -- ^ New counter.
+count = L.foldl' (flip update) M.empty
+
+{-|
+  Returns the union of two counters.
+-}
+union ::
+	(Ord k, Num v)
+	=> Counter k v -- ^ First counter.
+	-> Counter k v -- ^ Second counter.
+	-> Counter k v -- ^ Union of both counters.
+union = M.unionWith (+)