17 Jan
2009
17 Jan
'09
9:32 p.m.
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 [1..5]) $ \i -> do { print i; return i } 1 2 3 4 5 [1,2] 3 [4,5]
which I believe is proper. I'm undecided about allowing them to be empty. I don't know the theory or math behind zippers (I'm sure there are some papers written about it), but it doesn't make much sense to be empty. I got that impression from #haskell, also. Thanks for the comments. :) Jeff Wheeler