Merge sort README in Haskell

merge-sort.hs

@@ -0,0 +1,27 @@
+-- # Binary Search in Haskell
+-- This is an implementation of simple Binary Search in Haskell on any type that can be ordered.
+-- Binary Search is an effective searching algorithm, that can be used to find an element in a sorted list in O(lg(n)) time.
+
+-- Binary search with index carry
+bsWithIndex :: (Ord a) => [a] -> a -> Int -> Maybe Int
+bsWithIndex list n i
+    | n == head list        = Just i
+    | len == 1              = Nothing   -- only candidate in list is not the right elem
+    | n < head ys           = bsWithIndex xs n i
+    | otherwise             = bsWithIndex ys n (i + half)
+    where 
+        len         = length list
+        half        = len `div` 2 
+        (xs, ys)    = splitAt half list
+
+-- Binary search returning index, or -1 if element not in list
+bs :: (Ord a) => [a] -> a -> Int
+bs list n = case bsWithIndex list n 0 of
+    Just x  -> x
+    Nothing -> -1
+
+main :: IO ()
+main = do
+    let intList = [1,4,7,10,25,30]
+    print $ bs intList 29  -- 29 -> -1 as not in list
+    print $ bs intList 7   --  7 ->  2 as in list