Hi,
(I also sent this to libraries@, but without response; I'm posting here
for a wider audience.)
I'm somewhat of a beginner in Haskell, so take what I say with a grain
of salt, please.
The ListZipper implementation seems very odd to me, and #haskell seemed
to agree with me. The current
This traverses the list three times (reverse, init and last are each
linear time):
fromListEnd xs = Zipper (reverse $ init xs) (last xs) []
But we only need to do it once:
fromListEnd xs = let x:xs' = reverse xs in Zipper xs' x []
I don't *think* this has an effect on strictness/laziness, since
On Sat, 2009-01-17 at 10:44 -0800, Max Rabkin wrote:
This traverses the list three times (reverse, init and last are each
linear time):
fromListEnd xs = Zipper (reverse $ init xs) (last xs) []
But we only need to do it once:
fromListEnd xs = let x:xs' = reverse xs in Zipper xs' x []
I
On Sat, 2009-01-17 at 21:55 +0100, Jean-Philippe Bernardy wrote:
I think it should admit empty, and the traversable instance should
traverse the first list in reverse.
I fixed the latter issue so that the behavior is correct (I think).
I tested it like this:
forM (next $ next $ fromList
On Sat, Jan 17, 2009 at 4:32 PM, Jeff Wheeler j...@nokrev.com wrote:
On Sat, 2009-01-17 at 21:55 +0100, Jean-Philippe Bernardy wrote:
I think it should admit empty, and the traversable instance should
traverse the first list in reverse.
I fixed the latter issue so that the behavior is
On Sat, 2009-01-17 at 17:41 -0500, David Menendez wrote:
That's correct, but I think you'd be better off defining OpApplicative
(or Backward, as I call it) locally and avoiding the two reverses.
I'll have to look into this more; I don't really understand applicatives
right now, so I can't use
On Sat, Jan 17, 2009 at 7:49 PM, Jeff Wheeler j...@nokrev.com wrote:
On Sat, 2009-01-17 at 17:41 -0500, David Menendez wrote:
That's correct, but I think you'd be better off defining OpApplicative
(or Backward, as I call it) locally and avoiding the two reverses.
I'll have to look into this
On Sat, 17 Jan 2009, David Menendez wrote:
instance Applicative f = Applicative (Backwards f) where
pure = B . pure
f * x = B (unB f ** unB x)
probably should be f * x = B (unB x ** unB f)
anyhow, this should be part of Control.Applicative.
This may be terminological confusion. I
On Sat, Jan 17, 2009 at 9:13 PM, rocon...@theorem.ca wrote:
On Sat, 17 Jan 2009, David Menendez wrote:
instance Applicative f = Applicative (Backwards f) where
pure = B . pure
f * x = B (unB f ** unB x)
probably should be f * x = B (unB x ** unB f)
I always get that backwards.
