Another perfectly cromulent definition is:
untilNothing f = fromJust . last . takeWhile isJust . iterate (f =<<) . Just
This has 2 advantages:
1. It illustrates the haskellism that "A list is a loop is a list."
2. It composes much-beloved list combinators into a reasonable pipeline.
-- Kim-Ee
On Fri, Jul 21, 2017 at 12:26 AM, Jake
I have a function f :: a -> Maybe a that I want to feed into itself with some initial input until it returns Nothing.
untilNothing :: (a -> Maybe a) -> a -> a untilNothing f x = case f x of Just x' -> untilNothing f x' Nothing -> x
Is there a better way to do this? I feel like there is something more general going on with Monads being fed into themselves, but maybe I'm wrong. Thoughts?
_______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.