On Feb 2, 2008 12:11 PM, Chaddaï Fouché <chaddai.fouche@gmail.com> wrote:
To address this I propose this function :
foldl1MArray' :: (MArray a e m, Ix i) => (e -> e -> e) -> a i e -> m e
foldl1MArray' f a = do
(l,u) <- getBounds a
firstElem <- readArray a l
foldM (\a mb -> a `seq` mb >>= return . f a)
firstElem (map (readArray a) (range (l,u)))
I played with your foldl1MArray' last night. I noticed it can be reduced to . . .
foldl1MArray' :: (MArray a e m, Ix i) => (e -> e -> e) -> a i e -> m e
foldl1MArray' f a = do
(l,u) <- getBounds a
foldl1' (liftM2 f) (map (readArray a) (range (l,u)))
Unfortunately, my new version consumes a lot of stack and heap space. Why is this so inefficient? Is there a simple change that will make it efficient?