FP certainly means that you get immutable data structures (and that you don't get or at least don't use mutable data structures, by the definition of FP); Lisp

FP certainly means that you get immutable data structures (and that you don't get or at least don't use mutable data structures, by the definition of FP); Lisp - I dunno, CL has setf (and singly linked lists made of cons cells which can share a tail where you can modify the shared tail when working with of one of the lists and the other will get modified as well). As to a "good" concurrency system, that's a bit harder to define.