30 Nov
2011
30 Nov
'11
7:51 a.m.
On Wed, Nov 30, 2011 at 4:54 AM, Liyang HU
Evan Laforge
writes: 5) `toDescList` exists in Map, but not in IntMap, Set or IntSet. Without this function there's no way to (efficiently) iterate over a map backwards, which is pretty essential for an ordered collection!
How about using the Down/Dual/Desc/Converse/Opposite/Reverse newtype discussed in another recent thread, and providing for Data.Map:
reverse :: Map k a -> Map (Reverse k) a reverse Tip = Tip reverse (Bin n k a l r) = Bin n (Reverse k) a (reverse r) (reverse l)
(Arguably we also need reverse' :: Map (Reverse k) a -> Map k a. Hmm...)
reverse' :: Map (Reverse k) a -> Map k a reverse' = unsafeCoerce . reverse Sorry, couldn't resist =). Cheers, -- Felipe.