Chris F Clark wrote:
> Very impressive. It looks right to me and simple enough to
> understand. I must find the time to learn a modern FP language. Can
> you write a fold for this that prints the data as a binary tree of
> triples? I have to believe it isn't that hard....
{- Refactoring this as a fold is left as an exercise to the reader -}
data Clark a b c = Nil | Cons a (Clark b c (a,a)) deriving Show
clark =
(Cons 42 (Cons 3.14 (Cons "abc"
(Cons (1,2) (Cons (1.2,3.4) (Cons ("foo","bar")
(Cons ((9,8),(7,6)) (Cons ((0.1,0.2),(0.3,0.4))
(Cons (("w","x"),("y","z")) Nil)))))))))
main = print (toTree clark)
data Tree a = Empty | Node a (Tree a) (Tree a) deriving Show
toTree :: Clark a b c -> Tree (a,b,c)
toTree (Cons x (Cons y (Cons z rest)))
= Node (x,y,z)
(toTree (fst (lift_c rest)))
(toTree (snd (lift_c rest)))
toTree _ = Empty
lift_c :: Clark (a,a) (b,b) (c,c) -> (Clark a b c, Clark a b c)
lift_c Nil = (Nil,Nil)
lift_c (Cons (x,y) rest) = (Cons x (fst (lift_c rest)),
Cons y (snd (lift_c rest)))
--
http://mail.python.org/mailman/listinfo/python-list
