Section LINK_LIST.
Context {A: Type} {LA: Linker A}.
Fixpoint link_list (l: nlist A) : option A :=
match l with
| nbase a => Some a
| ncons a l =>
match link_list l with None => None | Some b => link a b end
end.

Lemma link_list_linkorder:
forall a l b, link_list l = Some b -> nIn a l -> linkorder a b.