[whateveracct]

okasaki came first

haskell too had them (IntMap honestly works fine in that use case)

[Sesse__]

Yeah, “Purely Functional Data Structures” came out in 1996! I read most of it recently, when I needed a C++ copy-on-write hash map. It was still fairly relevant (although the “obvious” solution of a HAMT was also the one we decided on).