Often one wants to build up a list of things
incrementally; this is
usually done using ` CONS`. First, note that for any ` x`,

` (CONS x NIL)` = ` (LIST x)` :

(CONS 'A NIL) = (A) (CONS '(A) NIL) = ((A))

Second, if ` LST` is a list, then ` (CONS x LST)`
will make a new list with ` x` as its first element, followed by
the other elements of ` LST`.

(CONS 'A '(B C)) = (A B C) (CONS '(A) '(B C)) = ((A) B C)