[ScottBurson]

> Lisp lists lack encapsulation; they are not opaque bags with which you do things like (add list item). That takes getting used to: always capturing the result value of a list construction.

You're conflating two properties: lack of encapsulation and functional update. It's true that lists expose their internal structure as conses, and it's also true that they're usually updated functionally (requiring, as you say, capturing the result), but these properties don't have to go together. It's entirely possible, and arguably desirable, to have functional collections -- where instances are immutable, but which provide operations for creating new instances from existing ones -- which are also opaque data types; see for example FSet [0]. Conversely, it's possible to have fully-mutable lists that expose their internal structure; you just have to wrap each list in a mutable cell. It would be ugly, and I don't know why you'd do it, but it's entirely possible.

[0] https://github.com/slburson/fset

[kazinator]

You're right; encapsulation doesn't mean mutable state; it means combining code and data (making a capsule).

Lisp list aren't ... whatever you call those stateful collection things that you can mutate with a list.add(42) type code that people are used to in a lot of scripting languages nowadays. That will trip up people who are used to that sort of thing.