Felipe Lessa wrote:

The builds seem fine, but we spot a (length xs) on the beginning. Maybe this is the culprit? We already know the size of the map (it was serialized), so it is just a matter of exporting

fromDistinctAscSizedList :: Int -> [(k, a)] -> Map k a

Excellent idea, what does stop you? fromDistinctAscList is already a function with a precondition that is not checked.

Too bad 'Map' is exported as an abstract data type and it's not straighforward to test this conjecture. Any ideas?

One really doesn't want to see the actual implementation (except for debugging or tuning purposes), but maybe conversions to and from a fully (and uniquely) balanced binary tree are desirable. (a basic binary tree data type is still missing on hackage). I think, equal maps should not yield different serialization results just because the internal tree structure happens to be different, but that's of course debatable. Cheers Christian Maybe the discussion should be continued on libraries@haskell.org?