在Scheme中查找列表的最大值和最小值

(max (list x y z) (min (list x y z)))

(define (find-max-min list)
  (if (null? list)
      'error
      (let ((max-value (car list))
            (min-value (car (cdr list))))
        (if (not (null? (cdr list)))
            (find-max-min (cdr list))
            (set! max-value (cdr list))
            (set! min-value (cdr (cdr list))))
        (if (not (null? max-value))
            (set! min-value (min min-value max-value))
            (set! min-value max-value))
        (list min-value max-value))))

(define (find-max-min list)
  (if (null? list)
      'error
      (let ((max-value (list (car list))))
        (if (not (null? (cdr list)))
            (find-max-min (cdr list))
            (set! max-value (cdr list))))
        (if (not (null? max-value))
            (set! max-value (max (car max-value) (car (cdr max-value))))
            (set! max-value (car list)))
        (list max-value (car list))))