`fastpair` for points in disjoint sets?

[jGaboardi]

I curious about the possibility of utilizing the fastpair data structure for querying nearest neighbors in disjoint sets à la cross $k$-nearest, for example. Would that even be possible with fastpair?

[carsonfarmer]

Well I think probably yes, and no. Yes, because you can certainly do this... however, to do it efficiently, you need to essentially add any new points to the data structure before doing the query. In fact, my implementation with _get_neighbor is unfortunately, not very safe, as it mutates the structure in place. That should probably be fixed before attempting to do cross-set queries.