<br />
<b>Deprecated</b>:  The each() function is deprecated. This message will be suppressed on further calls in <b>/home/zhenxiangba/zhenxiangba.com/public_html/phproxy-improved-master/index.php</b> on line <b>456</b><br />
;;; BASIC PROCEDURES for TREES
;; 
;; the-empty-tree: (tree T)
;; tree-cons: (-> ((or T (tree T)) (tree T))
;;                (tree T))
;; tree-empty?: (-> ((tree T)) boolean)
;; tree-first: (-> ((tree T))
;;                 (or T (tree T)))
;; ; REQUIRES: the tree is not empty
;; 
;; tree-rest: (-> ((tree T)) (tree T))
;; ; REQUIRES: the tree is not empty


(define the-empty-tree '())
(define tree-cons cons)
(define tree-empty? null?)
(define tree-first car)
(define tree-rest cdr)

(define atomic-item?
  ; TYPE: (-> (datum) boolean)
  (lambda (x)
    (not (or (pair? x)
	     (null? x)))))

(define sum-all
  ; TYPE: (-> ((tree number)) number)
  (lambda (ton)
    ; ENSURES: result is the sum of
    ;    all the numbers in ton
    (cond
      ((tree-empty? ton) 0)
      ((number? (tree-first ton))
       (+ (tree-first ton)
	  (sum-all (tree-rest ton))))
      (else (+ (sum-all (tree-first ton))
	       (sum-all (tree-rest ton))))
      )))


(DEFINE tdepth
  ; TYPE: (-> ((tree atomic-item)) number)
  (LAMBDA (tr)
    (COND
     [(tree-empty? tr) 0]
     [(atomic-item? (tree-first tr))
      (max 1 (tdepth (tree-rest tr)))]
     [ELSE
       (max
	 (add1 (tdepth (tree-first tr)))
	 (tdepth (tree-rest tr)))])))

(DEFINE remove-left-most
  ; TYPE: (-> ((atomic-item
  ;            (tree atomic-item)))
  ;           (tree atomic-item))
 (LAMBDA (item tr)
  (COND
   [(tree-empty? tr) '()]
   [(atomic-item? (tree-first tr))
    (COND
      [(equal? item (tree-first tr))
       (tree-rest tr)]
      [ELSE (tree-cons
	      (tree-first tr)
	      (remove-left-most
		item
		(tree-rest tr)))])]
   [ELSE
    (COND
      [(member-all? item (tree-first tr))
       (tree-cons (remove-left-most
			 item
			 (tree-first tr))
            (tree-rest tr))]
     [ELSE (tree-cons
	     (tree-first tr)
	     (remove-left-most
	       item
	       (tree-rest tr)))])])))


; - Program 4.16, pg. 113 -

(define member-all?
  (lambda (item ls)
    (if (null? ls) 
        #f
        (or (equal? (car ls) item)
            (and (not (pair? (car ls)))
                 (member-all? item (cdr ls)))
            (and (pair? (car ls))
                 (or (member-all? item (car ls))
                     (member-all? item (cdr ls))))))))

; - End Program -


(DEFINE depth
 ; TYPE: (-> (s-expression) number)
 (LAMBDA (item)
  ; ENSURES: result is the maximum depth
  ;          of item 
  (COND
   [(atom? item) 0]
   [(pair? item)
    (max (add1 (depth (car item)))
         (depth (cdr item)))])))