I can speak for Erlang when coming to immutable data structures and the memory issue. Since erlang's processes are basicaly a recursive function, once the proce

I can speak for Erlang when coming to immutable data structures and the memory issue. Since erlang's processes are basicaly a recursive function, once the process dies or it calls itself (with tail-call optimization), unused structures dies out quickly. Also changing an immutable data structure does not make a whole copy but rather a "diff". And since processes are completely isolated, garbage collection is easy (and doesn't hang the whole runtime), so the memory argument has been solved for some time, not by the language, but by the runtime.