30 Nov
2011
30 Nov
'11
1:54 a.m.
Evan Laforge
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...) Only problem right now is that Map is spine-strict, so the above is O(n). Would this fuse with to(Asc)List? Cheers, /Liyang