Sticking tombstones in the backing array doesn't actually cost you anything though. The backing array still needs to be the same size. Like maybe you end up hav

Sticking tombstones in the backing array doesn't actually cost you anything though. The backing array still needs to be the same size. Like maybe you end up having to re-hash more often? >Because of Hyrum's law even if you don't promise ordering (as Python's "Compact Dict" developer proposes at one point) your users will rely upon it and you're stuck with whatever you implemented. This is a real cost for a language or standard library. Look at the sad state of C++ standard collections. Yes but this cost goes away if you commit to it, and the alternative (like what go does) to force the order to change all the time also comes with a complexity cost vs. doing "nothing" and having the order be arbitrary and sometimes, but not actually, reliable.