Linked List
A list of sequentially linked nodes. This allows efficient insertion of nodes to the front of the list:
julia> l1 = nil()
nil()
julia> l2 = cons(1, l1)
list(1)
julia> l3 = list(2, 3)
list(2, 3)
julia> l4 = cat(l1, l2, l3)
list(1, 2, 3)
julia> l5 = map((x) -> x*2, l4)
list(2, 4, 6)
julia> for i in l5; print(i); end
246