Immutable strucutres allow you to sharing or keeping multiple versions. For instance moddeling gamestate as an immutable tree so the ai can cheaply try differe

Immutable strucutres allow you to sharing or keeping multiple versions. For instance moddeling gamestate as an immutable tree so the ai can cheaply try different options. Also sometimes it's still simpler. Exception handling on windows uses a thread local immutable linked list of handlers.