title: Racket inorder(tree) returns list
body: <p>I created an inorder function like this:</p>
  
  <pre><code>(define inorder
    (λ (tree) 
              (unless(empty? (node-left tree)) (inorder(node-left tree)))
              (print (node-x tree))
              (unless(empty? (node-right tree)) (inorder(node-right tree)))
    )
  )
  </code></pre>
  
  <p>How can I create a list with all the node-x tree elements instead of printing them. I need my inorder function to return a list of those elements.
  I tried using an auxiliary function but it didn't work...</p>