2.17¶

; Define a procedure last-pair that returns the list that contains 
; only the last element of a given (nonempty) list:
; (last-pair (list 23 72 149 34)) 
; (34)

(define (last-pair items)
    (if (null? (cdr items))
        items
        (last-pair (cdr items))))

(last-pair (list 23 72 149 34)) ;Value 2: (34)
(last-pair (list 12)) ;Value 3: (12)