stack.hs

module Stack(Stack, empty, pop, push, s) where
 
newtype Stack a = Stack [a] deriving Show
 
empty :: Stack a
empty = Stack []
 
pop :: Stack a -> (a, Stack a)
pop (Stack (x:xs)) = (x, Stack xs)
 
push :: a -> Stack a -> Stack a
push x (Stack xs) = Stack (x:xs)
 
s = push 5 $ push 4 $ push 3 $ push 2 $ push 1 $ empty