wren ng thornton
On 6/9/11 10:17 PM, Liyang HU wrote:
fromSet :: (Key -> a) -> IntSet -> IntMap a One downside of using fromSet is that it clones the IntSet before differencing. Since IntSet is spine-strict, this can be quite expensive since it'll clone the whole thing no matter how much is used.
I like the idea of having a fromSet function with the (Key->a) argument. But there's also room for differenceKeysSet for efficiency reasons. Perhaps you can come up with some fusion rules to get rid of the overhead of difference m (fromSet f s)?
There's precisely this rule in patch 0005 on the ticket.
Certainly there should be the rule: map f . fromSet g = fromSet (f . g) and similar for the other mapping functions.
I have a bunch of similar RULES in my own code already… (map, filter &c.) Should probably file them under a separate ticket. Cheers, /Liyang