Nix: Lazy Linked List Implementation using Nested Attribute Sets. This example specifically reifies the fibonnaci sequence into a lazy linked list.

linked_list.nix

# nix lists are not lazy linked lists
# we can however create lazy linked list using nested attribute sets, where the head is the node value and the tail is the nested cons

# we've basically created a recursive union type:
# type stream a = nil | { head = a; tail = stream a; }
# it's basically a lazy linked list!!!!

let
    # O(n) access of the linked list, it needs to unwrap the linked list as it goes deeper into the list
    streamElemAt = s: i:
        if i == 0
        then s.head
        else streamElemAt s.tail (i - 1);
    # recursively creates a nested attribute set, with a head node and tail cell
    fibsFrom = first: second: 
        {
            head = first;
            tail = fibsFrom second (first + second);
        };
    # wrapper function constructing a fibonnaci linked list with 1 and 1 as the first and second
    fibs = fibsFrom 1 1;
in
    streamElemAt fibs 30 
    # ^--------- HOLY SHIT A LINKED LIST! A LAZY LINKED LIST!!! So now we can get any fibonnaci number just by using the fibs stream, this basically reifies the fibonnaci sequence, so you can now use it explicitly as a primitive object!