Lists are extremely common in high-level programming.

sealed trait List[+A]
final case object Nil extends List[Nothing]
final case class Cons[A](h: A, t: List[A]) extends List[A]
            

Singly-linked list, however, unlike what you may be used to, lists are immutable! We prepend to lists, not append^[13] and we do not do it destructively.

Immutability leads to sharing. You can pass your list all around the place and nobody is going to update it — not just by promise, but not even the most malicious method could.