Is it possible to make a cycle in an immutable linked list?

Question

Suppose that we have the following structure in Java:

class List {
  // we're immutable
  final List next;
  final int value;

  public List(int value, List next) {
    this.next = next;
    this.value = value;
  }
}

Scala has built-in support for immutable singly-linked list. It would be:

val l = List(1, 2, 3) // immutable

So, is it possible to make a cycle in this kind of lists (immutable singly-linked list). By cycle, I mean the following:

Answer 1

You should use lazy collection to create infinite collection. You could use Stream:

def loopStream: Stream[Int] = {
  lazy val loop: Stream[Int] = 3 #:: 4 #:: 5 #:: 6 #:: 7 #:: 8 #:: loop
  1 #:: 2 #:: loop
}

loopStream.take(22).toList
// List(1, 2, 3, 4, 5, 6, 7, 8, 3, 4, 5, 6, 7, 8, 3, 4, 5, 6, 7, 8, 3, 4)