27_same_fringe.rkt

#lang slideshow
(require racket/control)
;; http://pllab.is.ocha.ac.jp/~asai/cw2011tutorial/main-j.pdf
;; ツリーは空リストか(left, int, right)のトリプレット

(define (walk tree)
  (if (null? tree)
      '()
      (let ((t1 (car tree)) (n (cadr tree)) (t2 (caddr tree)))
        (walk t1)
        (print n)
        (walk t2))))


(walk (list (list '() 2 '()) 1 '()))

(define (yield n)
  (shift k (list n k)))

(define (walk2 tree)
  (if (null? tree)
      '()
      (let ((t1 (car tree)) (n (cadr tree)) (t2 (caddr tree)))
        (walk2 t1)
        (yield n)
        (walk2 t2))))
(let ((hoge (reset (walk2 (list (list '() 2 '()) 1 '())))))
  (print (car hoge))
  (let ((fuga ((cadr hoge) '())))
    (print (car fuga))))

(print 'hoge)

;; treeの値と継続のペアをかえす
(define (start tree)
  (reset (walk2 tree)))

(define (print_nodes tree)
  (define (loop r)
    (if (null? r)
        '()
        (let ((n (car r)) (k (cadr r)))
          (print n)
          (loop (k '())))))
  (loop (start tree)))
(print_nodes (list (list '() 2 '()) 1 '()))
      

(define (same_fringe t1 t2)
  (define (loop r s)
    (cond
      [(and (null? r) (null? s)) 'True]
      [(and (not (null? r)) (not (null? s)))
       (let ((rn (car r)) (rk (cadr r)) (sn (car s)) (sk (cadr s)))
         (if (= rn sn)
             (loop (rk '()) (sk '()))
             'False))]
      [else 'False]))
  (loop (start t1) (start t2)))
(let ((tree1 (list (list '() 2 '()) 1 '()))
      (tree2 (list (list '() 3 '()) 1 '())))
  (print (same_fringe tree1 tree1))
  (print (same_fringe tree1 tree2)))