[superjan]

My intuition was indeed trained a long time ago. In terms of memory use, the current choice is likely optimal. But I have a hard time believing that doing an or operation on two sets of sorted numbers will be as fast as the same for two bitmaps of 8k. The latter can be trivially simd accellerated, and could be done in-place.

Having said that, I applaud that this type of datastructure is being investigated. An efficient bitset should be present in every collections library.