blob: 26967d23017eadba54be00c40747fae3308dfb04 (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
|
module fold
import StdEnv
:: List a = Nil | Cons a (List a)
(~>) infixr 4 :: (a (List a) -> List a)
(~>) = Cons
foldr :: (a -> b -> b) b (List a) -> b
foldr f x Nil = x
foldr f x (Cons a l) = f a (foldr f x l)
map :: (a -> b) -> (List a) -> (List b)
map f = foldr (Cons o f) Nil
sum = foldr (+) zero
product = foldr (*) one
any = foldr (||) False
all = foldr (&&) True
copy = foldr Cons Nil
append a b = foldr Cons b a
length = foldr (\_ n -> n + 1) 0
:: Tree a = Node a (List (Tree a))
(@) infixr 4 :: (a (List (Tree a)) -> Tree a)
(@) = Node
foldtree :: (a -> b -> c) (b -> c -> b) b (Tree a) -> c
foldtree f g a (Node l ts) = f l (foldtree` f g a ts)
where
//foldtree` :: (a -> b -> c) (c -> b -> b) b (List (Tree a)) -> b ??
foldtree` f g a (Cons t r) = g (foldtree f g a t) (foldtree` f g a r)
foldtree` f g a Nil = a
Start = map ((*)2) (5 ~> 10 ~> Nil)
|
