:: depth first library
::
|%
++  traverse
  |=  t=(tree @)
  ^-  (list @)
  ?~  t
    ~
  %+  weld
    (traverse l.t)
  %+  weld
    (traverse r.t)
  [n.t ~]
++  search
  |=  [t=(tree @) x=@]
  ^-  ?
  ?~  t
    %.n
  ?|  (search l.t x)
      (search r.t x)
      =(n.t x)
  ==
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