Proposal: Allow gunfold for Data.Map, Data.IntMap, etc.

Johan Tibell johan.tibell at
Thu Aug 30 02:02:35 CEST 2012

On Wed, Aug 29, 2012 at 4:54 PM, Edward Kmett <ekmett at> wrote:
> We should be able to fuse this "try to construct linearly, but fall back on
> N-log-N" version of fromList in one pass even for normal uses of fromList.
> e.g. assume that you are constructing a sorted tree until you find a key out
> of order, then take the tree you've built so far and union it appropriately
> with the slower constructed fromList of the remainder. That way you don't
> have to retain the storage for both the list and the map, and we only force
> the list once.

Could you instead of falling back to the slower fromList just keep
building new trees and then union them all in the end. Real world data
is often is semi-sorted order. I guess we would need to detect some
worst case scenarios (i.e. sorted in reverse order) and fall back to
the slower fromList in those cases.

-- Johan

More information about the Libraries mailing list