; (ins-sort lon) returns a sorted list of the nubers 
; that are in lon. Because it is easier to add to the front 
; of a Scheme list than to the end, the sorting starts at the 
; end of the list.

(define ins-sort
  (lambda (lon) ; fill in the details
   (if (or (null? lon) (null? (cdr lon)))   ; (= (length lon) 1) is a bad idea for this
	   lon
	   (let ([sorted-cdr (ins-sort (cdr lon))])
	     (insert (car lon) sorted-cdr)))))


(define insert
  (lambda (n sorted-list) ; fill in the details
    (cond [(null? sorted-list) (list n)]
	  [(<= n (car sorted-list)) (cons n sorted-list)]
	  [else (cons (car sorted-list)
		      (insert n (cdr sorted-list)))])))
	   
    ))


(ins-sort '())
(ins-sort '(3 7 -2 9 7 6 4))