(de nextLeaf (Rt Tree)
   (co Rt
      (recur (Tree)
         (when Tree
            (recurse (cadr Tree))
            (yield (car Tree))
            (recurse (cddr Tree)) ) ) ) )

(de cmpTrees (Tree1 Tree2)
   (prog1
      (use (Node1 Node2)
         (loop
            (setq
               Node1 (nextLeaf "rt1" Tree1)
               Node2 (nextLeaf "rt2" Tree2) )
            (T (nor Node1 Node2) T)
            (NIL (= Node1 Node2)) ) )
      (co "rt1")
      (co "rt2") ) )