I think a lot of the pain in Scala/Rust etc immutable data structures comes down to static typing. In Clojure for instance you can very ergonomically do deeply

I think a lot of the pain in Scala/Rust etc immutable data structures comes down to static typing. In Clojure for instance you can very ergonomically do deeply nested persistent updates. (update-in {:foo [{:bar ["a"] :baz ["b" "c" "d"]}]} [:foo 0 :baz 1] clojure.string/capitalize) => {:foo [{:bar ["a"], :baz ["b" "C" "d"]}]}