; largest : non-empty-list-of-numbers -> number
(define (largest nums)
  (local [(define (bigger x y)
            (cond [(>= x y) x]
                  [else y]))
          (define (helper nums)
            (cond [(empty? (rest nums)) (first nums)]
                  [(cons? (rest nums))
                   (bigger (first nums) (helper (rest nums)))]))]
    (helper nums)))
(largest (list 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1)) "should be" 16
(largest (list 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16)) "should be" 16