-- by Chris Okasaki, /ICFP'00/.
unfoldForestM_BF :: Monad m => (b -> m (a, [b])) -> [b] -> m (Forest a)
unfoldForestM_BF f = liftM (reverseOnto []) . unfoldForestQ f . listToQueue
- where reverseOnto :: [a] -> Queue a -> [a]
+ where reverseOnto :: [a'] -> Queue a' -> [a']
reverseOnto as q = case deQueue q of
Nothing -> as
Just (a, q') -> reverseOnto (a:as) q'
tQ <- unfoldForestQ f (foldl addToQueue aQ as)
let (ts, tQ') = splitOnto [] as tQ
return (addToQueue tQ' (Node b ts))
- where splitOnto :: [a] -> [b] -> Queue a -> ([a], Queue a)
+ where splitOnto :: [a'] -> [b'] -> Queue a' -> ([a'], Queue a')
splitOnto as [] q = (as, q)
splitOnto as (_:bs) q = case fromJust (deQueue q) of
(a, q') -> splitOnto (a:as) bs q'