Min

; get-level връща всички атоми от даденото ниво.
; след това просто прилагаме min на резултата.
(define (get-level xss level)
  (cond ((null? xss) '())
        ((and (atom? (car xss)) (= level 0))
        (cons (car xss) (get-level (cdr xss) level)))
        ((and (pair? (car xss)) (> level 0))
         (append (get-level (car xss) (- level 1))
                 (get-level (cdr xss) level)))
        (else (get-level (cdr xss) level))))

(define (get-min xss level)
  (apply min (get-level xss level)))

(define test '((1) 3 (7 (9)) (4 (8))))