Function returning the place of an element in a tree

gistfile1.el

(defun place-of (item tree)
  (let ((place (place-of-1 item tree "")))
    (and place
      (intern (concat "c" place "r")))))

(defun place-of-1 (item tree place)
  (cond
   ((null tree))
   ((consp tree)
    (let (found)
      (while (and tree (not found))
        (unless (setq found (place-of-1 item (car tree) (concat "a" place)))
          (setq place (concat "d" place))
          (setq tree (cdr tree))))
      found))
   (t (if (eq item tree) place))))