mergesort in haskell

mg.hs

mergesort :: Ord a => [a] -> [a]
mergesortM :: Ord a => [a] -> [a] -> [a]
mergesortM a [] = a
mergesortM [] a = a
mergesortM (a:ax) (b:bx)
     | a>b = [a] ++ (mergesortM ax ([b] ++ bx))
     | otherwise =[b] ++ (mergesortM ([a] ++ ax) bx)

mergesort [] = []
mergesort [a] = [a]
mergesort a = mergesortM (mergesort h) (mergesort t)
     where
       (h,t) = split a

split :: [a] -> ([a], [a])
split myList = splitAt (((length myList) + 1) `div` 2) myList

main = print (mergesort [1,5,6,2,7,3])