Hi, I’ll skip on the +1 and only make negative comments, as they are fewer :-) Am Montag, den 28.11.2011, 17:28 +0100 schrieb Milan Straka:
4) The functions `mapKeys :: Ord k2 => (k1->k2) -> Map k1 a -> Map k2 a` `mapKeysWith :: Ord k2 => (a -> a -> a) -> (k1->k2) -> Map k1 a -> Map k2 a` `mapKeysMonotonic :: (k1->k2) -> Map k1 a -> Map k2 a` have no IntMap correspondents. Both `mapKeys` and `mapKeysWith` can be defined by the user without loss of performance.
Solutions: (a) deprecate the `mapKeys*` methods from Map (b) add the `mapKeys*` methods to IntMap.
They seem useful to me to write legible code, therefore I’m in favor of (b). Also, they are used in the wild (random reference): http://darcswatch.nomeata.de/bundles/a3fbac8e4ce65d1426c5d1e0d19a6020f425b5d...
5) `toDescList` exists in Map, but not in IntMap, Set or IntSet.
Solutions: (a) deprecate `Map.toDescList` (b) add `toDescList` to IntMap. In this case, we should consider adding it also to Set and IntSet.
I have no strong opinion here. The `toDescList` can be trivially expressed as left fold. But it is currently a subject to list fusion. To vote for (a).
I have at least one project where I make heavy use of list fusion. In that case I only use toList, but one could imagine a case where I want that order. Therefore, I’m in favor of (b).
6) Result of discussion around http://hackage.haskell.org/trac/ghc/ticket/5242 Add `Map.fromSet :: (key -> a) -> Set key -> Map key a` `IntMap.fromSet :: (Int -> a) -> IntSet -> IntMap a` The implementation would exploit same structure of map and set (leave the shape of the original tree/trie, just adding values).
Cons: fromSet is a trivial composition: fromSet f = Map.fromDistinctAscList . map (\k -> (k, f k)) . Set.toAscList This can be defined by the user and is asymptotically optimal. Pro: performance. Also the performance of keysSet would improve, if the map can use data constructors of set.
I vote for adding these methods.
I very much agree (guess I don’t want to be only negative after all). Greetings and thanks for your work, Joachim -- Joachim "nomeata" Breitner mail@joachim-breitner.de | nomeata@debian.org | GPG: 0x4743206C xmpp: nomeata@joachim-breitner.de | http://www.joachim-breitner.de/