Create a gist now

Instantly share code, notes, and snippets.

What would you like to do?
data List a = Nil
| Cons a (List a)
deriving Show
xs = Cons 1 (Cons 2 (Cons 3 Nil))
reduceList f z Nil = z
reduceList f z (Cons x xs) = f x (reduceList f z xs)
idList = reduceList Cons Nil
mapList f = reduceList (Cons . f) Nil
filterList p = reduceList (\x xs ->
if p x then Cons x xs
else xs)
Nil
mapListIf p f = reduceList (\x xs ->
if p x then Cons (f x) xs
else Cons x xs)
Nil
appendList xs1 xs2 = reduceList Cons xs2 xs1
reverseList = reduceList (\x xs -> xs `appendList` (Cons x Nil)) Nil
data Tree a = Node a (List (Tree a)) deriving Show
tree = Node 1
(Cons (Node 2 Nil)
(Cons (Node 3
(Cons (Node 5 Nil)
(Cons (Node 6 Nil) Nil)))
(Cons (Node 4 Nil) Nil)))
reduceTree f g z (Node x trees) =
f x (reduceList g z (mapList (reduceTree f g z) trees))
idTree = reduceTree Node Cons Nil
mapTree f = reduceTree (Node . f) Cons Nil
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment