On Mon, May 23, 2005 at 01:48:14PM +0100, Adrian Hey wrote:
I'd like to know about the space behaviour of the folds and whether or not you need more fold variants.
Hmm, there are a number of choices just for foldr: foldr_l :: (a -> b -> b) -> b -> Seq a -> b foldr_l f z xs = case viewL xs of EmptyL -> z x :< xs' -> x `f` foldr_l f z xs' -- same result as foldr_l, but different performance foldr_r :: (a -> b -> b) -> b -> Seq a -> b foldr_r f z xs = case viewR xs of EmptyR -> z xs' :> x -> foldr_r f (x `f` z) xs' -- strict version foldr_r' :: (a -> b -> b) -> b -> Seq a -> b foldr_r' f z xs = case viewR xs of EmptyR -> z xs' :> x -> let z' = x `f` z in z' `seq` foldr_r' f z' xs' The current definition is equivalent to the first (but operates directly on the internal structure). I can't think of a situation where I'd want the second. The strict version would be useful, and probably a monadic version too (of which strictness could be a special case).