start with map reduce

src/MapReduce.hs

@@ -0,0 +1,38 @@
+module MapReduce where
+
+import Data.Char (toLower)
+import Data.List (sort, group)
+import Control.Arrow ((&&&)) 
+import Data.Map as Map hiding (map, filter)
+import Data.Monoid
+
+stringToWordCountMap :: String -> Map.Map String Int
+stringToWordCountMap  = Map.fromList . map (head &&& length) . group . sort . words . map toLower 
+
+combineWordCountMaps :: Map.Map String Int -> Map.Map String Int -> Map.Map String Int
+combineWordCountMaps = Map.unionWith (+)
+
+reduceWordCountMaps :: [Map.Map String Int] -> Map.Map String Int
+reduceWordCountMaps [x]    = x
+reduceWordCountMaps (x:xs) = combineWordCountMaps x (reduceWordCountMaps xs)
+
+--countWords :: String -> Map.Map String Int
+--countWords = 
+
+simpleMapReduce
+    :: (a -> b)      -- map function
+    -> ([b] -> c)    -- reduce function
+    -> [a]           -- list to map over
+    -> c             -- result
+simpleMapReduce mapFunc reduceFunc  = reduceFunc . Prelude.map mapFunc  
+
+filterBy :: String -> Char -> Bool
+filterBy notAllowedChars char = 
+     char `notElem` notAllowedChars
+
+mapReduceDemo = do
+    contents <- readFile "LICENSE"
+    let linesInFile = lines $ filter (filterBy ".,;:!?()[]{}\"'") contents
+    let result = simpleMapReduce stringToWordCountMap reduceWordCountMaps linesInFile
+    putStrLn $ "The file has " ++ show (length (lines contents)) ++ " lines!"
+    putStrLn $ "result = " ++ show result ++ "."