Yeah, that was the problem with most attempts I saw, unordered_map won't work. I did write a persistent hash map and vector [1], but ended up mostly using them

Yeah, that was the problem with most attempts I saw, unordered_map won't work. I did write a persistent hash map and vector [1], but ended up mostly using them in C++ projects. I wouldn't advise anyone else to use them at this level of testing/maturity though. Writing them was super interesting. 1: https://hg.sr.ht/~vnorilo/pcoll/browse https://hg.sr.ht/~vnorilo/pcoll/browse (not production quality)