[plt-scheme] Re: Help: I want to travel a binary tree?

Yes, it works!

my code:
--------------------
(define travsal (lambda (tree)
                 (cond
                   ((null? tree) ())
                   (#t (append (travsal (car tree)) (cons (cadr tree)
(travsal (caddr tree))))))))

(define tree1 '(((() 4 ()) 2 (() 5 ())) 1 ((() 6 ()) 3 (() 7 ()))))

(display tree1)
(newline)

(travsal tree1)
-------------------

the result is :
(((() 4 ()) 2 (() 5 ())) 1 ((() 6 ()) 3 (() 7 ())))

(4 2 5 1 6 3 7)


On 8月1日, 下午6时46分, Chris Uzdavinis <ch... at atdesk.com> wrote:
> Zeng Fucen <zengfu... at gmail.com> writes:
> > Thanks Joshua!
> > I'm used to using C/C++ , and I agree with you .
> > These days , when I started FP , every function use recursion !
> > That makes things a little interesing.
>
> If you can write a C++ template meta-program to traverse a tree, then
> it's a cakewalk in Scheme.  (And much prettier!)
>
> --
> Chris
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