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

On Jul 30, 2007, at 4:20 AM, Zeng Fucen wrote:

> I'm a scheme novice,
>
> I want to travel a binary tree, how to ? (depth first)
>
> Thanks for your tips , first!
>
> I define a tree like this:  (1 (2 4 5) (3 6 7))


If your collection of trees contains just this one S-expression,  
which looks like that as a tree:

+-----------+------------ ...
|           |
1    +------+------+
      |      |      |
      2      4      5

then your search result is '(1 2 4 5 3 6 7)

So I'd say the proper function definition is

(define (depth-first-traversal-of the-one-tree-that-is-my-possible- 
input)
   '(1 2 4 5 3 6 7))

Hope this helps. -- Matthias