Add merge sort

MergeSort.hs

@@ -0,0 +1,20 @@
+merge :: [Integer] -> [Integer] -> [Integer]
+merge [] lst = lst
+merge lst [] = lst
+merge (h1:t1) (h2:t2) = if h1 < h2 then
+  [h1] ++ merge t1 (h2:t2)
+  else
+  [h2] ++ merge (h1:t1) t2
+
+sort :: [Integer] -> [Integer]
+sort [] = []
+sort [x] = [x]
+sort lst = let
+  mid = div (length lst) 2
+  (left, right) = splitAt mid lst
+  in merge (sort left) (sort right)
+
+main :: IO ()
+main = let
+  lst = [10, 42, 2, 23, 666, 1, -94, 52]
+  in print $ sort lst