RecursiveFunctions.hs

and' :: [Bool] -> Bool
and' [] = True
and' (x:xs) = x && and' xs

concat' :: [[a]] -> [a]
concat' [] = []
concat' [[]] = []
concat' (x:xs) = x ++ concat' xs

replicate' :: Int -> a -> [a]
replicate' 0 a = []
replicate' n a = [a] ++ (replicate' (n-1) a)

(!!!) :: [a] -> Int -> a
(x:xs) !!! 0 = x
(x:xs) !!! n = xs !!! (n-1)

elem' :: Eq a => a -> [a] -> Bool
elem' a [] = False
elem' a (x:xs) = x == a || elem' a xs

merge :: [Int] -> [Int] -> [Int]
merge [] ys = ys 
merge (x:xs) ys = merge xs (smaller ++ [x] ++ larger)
                  where
                    smaller = [ a | a <- ys, a <= x ]
                    larger = [ b | b <- ys, b > x ]
                 
msort :: [Int] -> [Int]
msort [n] = [n]
msort xs = merge first second
                where
                  l = length xs
                  h = l `div` 2
                  first  = [a | (a,i) <- zip xs [0..l], i <= h]
                  second = [b | (b,j) <- zip xs [0..l], j > h]