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2018-03-13 15:38:11

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  1. #lang racket
  2. (define t '(10 (5(4(2 ()()) (26()())) (21(15()()) (23 ()()))) (11(6()())(13()()))))
  3.  
  4. (define (leaf? t) (null? t))
  5. (define (tree-left-branch t) (cadr t))
  6. (define (tree-right-branch t) (caddr t))
  7.  
  8. (define (tree-fn t)
  9.   (display `(visiting ,t))
  10.   (newline)
  11.   (if (leaf? t)
  12.       #f
  13.       (begin (tree-fn (tree-left-branch t))
  14.              (tree-fn (tree-right-branch t)))))
  15.  
  16. (tree-fn t)

=>

(visiting (10 (5 (4 (2 () ()) (26 () ())) (21 (15 () ()) (23 () ()))) (11 (6 () ()) (13 () ()))))

(visiting (5 (4 (2 () ()) (26 () ())) (21 (15 () ()) (23 () ()))))

(visiting (4 (2 () ()) (26 () ())))

(visiting (2 () ()))

(visiting ())

(visiting ())

(visiting (26 () ()))

(visiting ())

(visiting ())

(visiting (21 (15 () ()) (23 () ())))

(visiting (15 () ()))

(visiting ())

(visiting ())

(visiting (23 () ()))

(visiting ())

(visiting ())

(visiting (11 (6 () ()) (13 () ())))

(visiting (6 () ()))

(visiting ())

(visiting ())

(visiting (13 () ()))

(visiting ())

(visiting ())

#f