dpt at bostoncoop.net
Mon Nov 22 02:17:37 EST 2004
On Mon, Nov 22, 2004 at 09:41:47AM +0300, Serge D. Mechveliani wrote:
> Yes. Thank you.
> Inspecting Prelude, we find out that scanl expresses, mainly,
> the thing.
Did you find a good replacement for the second function, foldWhileJust?
Come to think of it, the way to do that would be to turn the accumulator
to a function from Maybe a to Maybe a, like this:
foldWhileJust :: (a -> b -> Maybe a) -> a -> [b] -> a
foldWhileJust f a =
let f' :: Maybe a -> b -> Maybe a
f' = maybe (const Nothing) f
in fromJust . last . takeWhile isJust . scanl f' (Just a)
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