As far as FP langugages go, LISP is very much a free-for-all. It can be pure if you want it to be, or stateful and imperative if you prefer. Nothing is really enforced like for example in Haskell.
For your use-case a mutable reference behind some type of synchronized accessor would probably suffice. If you want to get fancy you could design the system in such a way that any point in time could be replayed or rewound to, since you have the commands and the initial state.
For your use-case a mutable reference behind some type of synchronized accessor would probably suffice. If you want to get fancy you could design the system in such a way that any point in time could be replayed or rewound to, since you have the commands and the initial state.
Some ideas to look into:
[1] https://github.com/acid-state/acid-state
[2] https://docs.datomic.com/pro/getting-started/brief-overview....
[3] https://www.martinfowler.com/bliki/CQRS.html