List2

-- Linked List
data List a = Empty | Data a (List a) deriving (Show, Read, Eq, Ord)

-- new List
lnew :: a -> List a
lnew x = Data x Empty

-- add Element to end of List
ladd :: (List a) -> a -> List a
ladd Empty x = lnew x
ladd (Data x l) y = Data x (ladd l y)

-- add List to end of List
laddl :: (List a) -> (List a) -> List a
laddl Empty l = l
laddl l Empty = l
laddl (Data x1 l1) l2 = Data x1 (laddl l1 l2)

-- insert Element alphabetically
lins :: (Ord a) => (List a) -> a -> List a
lins Empty x = lnew x
lins (Data x l) y
    | x == y = Data x (Data y l)
    | x <  y = Data x (lins l y)
    | x >  y = Data y (Data x l)

-- List contains Element?
lhas :: (Eq a) => (List a) -> a -> Bool
lhas Empty _ = False
lhas (Data x l) y
    | x == y    = True
    | otherwise = lhas l y

-- length of List
llen :: (List a) -> Int
llen Empty = 0
llen (Data _ l) = 1 + (llen l)

-- remove Element from List
ldel :: (Eq a) => (List a) -> a -> List a
ldel Empty _ = Empty
ldel (Data x l) y
    | x == y    = l
    | otherwise = Data x (ldel l y)