toggle astah of the current 'let'

toggle-let-astah.el

(defun toggle-let-astah-search-let ()
  (save-excursion
    (let ((point-min (point-min))
          (re "(\\(lexical-\\)?let\\(\\*\\)?")
          (continue t) pos ast ret)
      (while (and continue (/= (point-min) (point)))
        (goto-char (or (ignore-errors (scan-lists (point) -1 1))
                       (point-min)))
        (save-excursion
          (when (and (looking-at re) (re-search-forward re nil t))
            (setq pos (match-end 0)
                  ast (match-string 2))
            (unless (ignore-errors (scan-lists (point) 1 0))
              (setq ret (cons pos ast)
                    continue nil)))))
      ret)))

(defun toggle-let-astah ()
  (interactive)
  (let (replaced (org-pos (point)))
    (save-excursion
      (let ((limit (or (save-excursion 
                         (re-search-backward "\\bdef" nil t))
                       (point-min)))
            pair pos ast)
        (save-restriction
          (narrow-to-region limit org-pos)
          (setq pair (toggle-let-astah-search-let)
                pos (car pair) ast (cdr pair))
          (when pos
            (goto-char pos)
            (cond
             (ast (delete-backward-char 1))
             (t (insert "*")))
            (setq replaced t)))))
    (cond
     (replaced (message "toggle let-aster !"))
     (t (message "let not found.")))))

;(define-key emacs-lisp-mode-map (kbd "C-8") 'toggle-let-astah)