I'm not sure about persistence, but it definitely has immutable data structures. See e.g. the docs on hash tables: https://docs.racket-lang.org/reference/hashta

I'm not sure about persistence, but it definitely has immutable data structures. See e.g. the docs on hash tables: https://docs.racket-lang.org/reference/hashtables.html https://docs.racket-lang.org/reference/hashtables.html As mentioned in the comments here, Racket's documentation is wonderful. I've yet to come across a better mix of technical reference, guiding narrative and a wealth of usage examples.