SICP questions 2.17 and 2.18

ex217_18.scm

;2.17
;(last-pair (list 23 72 89 124 34)) ; should be (34)
(define (last-pair x)
  (if (atom? (cdr x)) 
      x
     (last-pair (cdr x))))
        
(display (last-pair (list 23 72 89 124 34)))      
(newline)

; map-reduciness? Seems more like functional while loop        
; 2.18
(define (reverse-iter newl oldl)
  (if (atom? oldl)
      newl
    (reverse-iter (cons (car oldl) newl) (cdr oldl))))
  
; (reverse (list 1 2 3 4 5)); should be (5 4 3 2 1)
(define (reverse x) 
  (reverse-iter  `()  x))

(display (reverse (list 1 2 3 4 5)))
(newline)