Travis Erdman wrote:
I did not realize that the boxed arrays would have this extra-lazy behavior. The reason I chose boxed is because I needed to store these very large trees (custom data type) that I referenced in an earlier question. Since D.V.Unboxed and Storable don't appear to support non-standard data types, is there another package that might better fit my needs? Data.IntMap perhaps? I originally chose an array over a map because I need fast random access to individual elements (and cheap modification).
Concerning your choice of data structure, take note that data structures are *persistent* in Haskell, i.e. they cannot be mutated. So, while arrays provide random access in O(1) time, they need O(n) time to update because the whole array has to be copied (unless you ensure ephemeral use with the ST or IO monad). Nonetheless, the Data.Vector library provides functions like map that operate on the whole array and run in O(n) time. In comparison, Data.IntMap has O(size of Int in bits) lookup and O(size of Int in bits) update. Data.Vector is mainly about arrays of bytes, hence the prominence of Unboxed and Storable. You could make your tree an instance of Storable , but I think that's only possible for fixed size types anyway. Regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com