The global identifier null is bound to the empty list.
(reverse! list) is the same as (reverse list), but list is destructively reversed.
(append! list 
) destructively appends lists.
(list* v ) is similar to (list v )
but the last argument is used directly as the cdr of the last
pair constructed for the list:
(list* 1 2 3 4) ; => (1 2 3 . 4)