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Text File  |  1999-12-31  |  578 b   |  13 lines
  1. (define (pre-order tree)
  2.         (define (preorder-it tree pila out)
  3.                 (if (and (empty-tree? tree)(empty-pila? pila))
  4.                     out
  5.                     (if (empty-tree? tree)
  6.                         (preorder-it (top pila)
  7.                                      (pop pila)
  8.                                      out)
  9.                         (preorder-it (left-branch tree)
  10.                                      (push (right-branch tree) pila)
  11.                                      (append out (list (entry tree)))))))
  12.         (preorder-it tree make-pila '()))
  13.