title: How to move zipper to left/right node in clojure?
body: <p>I'm writing a tree ( business process decision tree ) in clojure data structure .    </p>
  
  <pre><code>(require clojure.zip :as z)
  
  (z/vector-zip 
      [ :billed?  
          [:yes  
              [:check-bank-account] 
              [:check-cash] ] 
          [:send-out-email] ])
  </code></pre>
  
  <p>when code walk on the first node, it will read the keyword and perform certain actions, the result will be True or False, then I would like it walk into <code>left</code> ( True) or <code>right</code> (False) node .</p>
  
  <p>When my code starts with root node, and call some function associated with <code>:billed?</code> it return a <code>True</code>, how could clojure walk into <code>:yes</code> node, or <code>:send-out-email</code> node ? I thought there is only <code>z/down</code> while, <code>left</code> or <code>right</code>is only for siblings not for directions of children.</p>
  
  <p>Thank you very much for your time and appreciate any thoughts</p>