Hello all, I was trying to implement >>= (tBind) on my "Temporal" data type and found that it hangs on an operation like takeInitialPart $ infiniteTemporal >>= (\x -> finiteTemporal) I am pretty sure the result is well defined and by no means infinite. Also the code works on finite Temporals. How does one address such problems? I attach the relevant pieces of code, in case someone would be so kind and inspect or run it. Feel free to point out any flaws as I might be completely off-track. If you call ex10 in GHCI, you get no result. The line marked with "< here" is executed over and over, but apparently without contributing to the result. The debugger shows, that "hd" does have a correct, finite value each time and that "tpr" is consumed as expected. -- -- -- -- -- -- -- -- -- examples -- -- -- -- -- -- -- ex1 = Temporal [(DPast, 1), (T 3,3), (T 7, 7)] :: Temporal Int ex10 = tUntil (T 5) $ outer `tBind` \_ -> ex1 :: Temporal Int where outer = Temporal $ (DPast,0):[(T (fromIntegral t), t)| t <- [5,10 ..]] -- -- -- -- -- -- -- -- -- tBind -- -- -- -- -- -- -- -- -- Changed (Temporal a) to (Temporal Int) for debugging tBind :: (Temporal Int) -> (Int -> Temporal Int) -> Temporal Int tBind tpr f -- tpr is infinite in this example, let's forget these cases -- | tNull tpr = error "empty Temporal" -- | tNull (tTail tpr) = laties | otherwise = let hd = (tUntil (tTt tpr) laties) in hd `tAppend` (tTail tpr `tBind` f) -- < here where laties = switchAt (tTh tpr) ( f (tVh tpr)) tTail (Temporal xs) = Temporal (tail xs) tAppend (Temporal as) (Temporal bs) = Temporal (as ++ bs) switchAt t tpx | tNull (tTail tpx) = Temporal (tot tpx) | between t (tTh tpx) (tTt tpx) = Temporal (tot tpx) | otherwise = switchAt t (tTail tpx) where tot (Temporal ((ty,vy):xs)) = ((max t ty, vy):xs) between t x y = t >= x && t < y -- -- -- -- -- -- -- -- -- helpers -- -- -- -- -- -- -- -- data Time = DPast | T Integer deriving (Eq, Show) -- DPast is "distant past" instance Ord Time where compare DPast DPast = EQ compare DPast _ = LT compare _ DPast = GT compare (T t1) (T t2) = compare t1 t2 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- data Temporal a = Temporal [(Time, a)] deriving (Eq, Show) tVh :: Temporal a -> a tVh = snd . head . toList -- value head tTt, tTh :: Temporal a -> Time tTt = fst . head . tail . toList -- time tail tTh = fst . head . toList -- time head tNull = null . toList tUntil :: Time -> Temporal a -> Temporal a tUntil t (Temporal xs) = Temporal $ (takeWhile (\(tx, vx) -> tx > t)) xs toList :: Temporal a -> [(Time, a)] toList (Temporal xs) = xs