DData

[Christian Maeder]

Simon Marlow wrote:
>>"FiniteMap Int a" performs better than "Map Int a", but not as good as
>>"IntMap a", but the differences are unimportant for us.
> 
> How much better?  I'm not keen to import something that's going to
> degrade performance of existing code noticeably.

Ok, I'll send you numbers (later). Are you going to reimplement 
FiniteMap via DData.Map (or how could existing code suffer)?

>>(We would need a pure HashMap with O(1) lookup while extending the
>>Map) 
> 
> Could you elaborate?

Actually an IntMap or Array where we never try to lookup an index that 
has not been set before and once it's set, we'll never change the 
corresponding entry while avoiding the monad of mutable arrays or the 
HashTable implementation.

Christian