(add-to-end '(5 4 3 2) 1) ⇒ (5 4 3 2 1)
Q: Adding element elt to the empty list produces what list?
A: (elt)
Q: How do you add elt to the end of a nonempty list?
(Hint: Answer recursively in terms of the head and tail.)
A: Add elt to the end of the tail and cons the head onto that
result.
(define add-to-end
(lambda (lst elt)
(if (null? lst)
(cons elt '())
(cons (car lst)
(add-to-end (cdr lst) elt)))))