t’s not necessary for correctness. He just thought it would be more elegant. I think I’ll just change the state for now. I can always create my own AppendOnlyList if I want to. I just wanted to make sure I wasn’t overlooking a common data structure. (I’m new to Kotlin but not to programming. I’m thinking from a Scheme perspective without set!)

the latter would be more scheme-like I’d think, but I’m no expert there

Scheme-like would be to have only immutable lists and create a new list every time you want to add an element. Not the most efficient. 🐌