On Sat, Nov 20, 2004 at 12:47:58PM +0300, Serge D. Mechveliani wrote: > Is such a function familia to the Haskell users? > > foldlWhile :: (a -> b -> a) -> (a -> Bool) -> a -> [b] -> a > foldlWhile f p a bs = > case > (bs, p a) > of > ([], _ ) -> a > (_, False) -> a > (b:bs', _ ) -> foldlWhile f p (f a b) bs' > > foldl does not seem to cover this.
Why not just
foldlWhile f p a bs = takeWhile p $ foldl f a bs
?
> More `generic' variant:
>
> foldlWhileJust :: (a -> b -> Maybe a) -> a -> [b] -> a
> foldlWhileJust f a bs = case bs of
>
> [] -> a
> b:bs' -> case f a b of Just a' -> foldlWhileJust f a' bs'
> _ -> a
I don't know a short way to rewrite this one yet.
Peace,
Dylan
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