如何使用 emacs/elisp 获取当前缓冲区信息的开始/结束？

我有以下代码运行以范围输入的Figlet。 如何修改此代码以检查 b 或 e 是否未指定，使 b 位于当前缓冲区的开头，e 位于当前缓冲区的结尾？

(defun figlet-region (&optional b e) 
  (interactive "r")
  (shell-command-on-region b e "/opt/local/bin/figlet" (current-buffer) t)
  (comment-region (mark) (point)))
(global-set-key (kbd "C-c C-x") 'figlet-region)

ADDED

肖恩帮助我找到了这个问题的答案

(defun figlet-region (&optional b e) 
  (interactive)
  (let ((b (if mark-active (min (point) (mark)) (point-min)))
        (e (if mark-active (max (point) (mark)) (point-max))))
   (shell-command-on-region b e "/opt/local/bin/figlet" (current-buffer) t)
  (comment-region (mark) (point))))
(global-set-key (kbd "C-c C-x") 'figlet-region)

像这样：

(defun figlet-region (&optional b e) 
  (interactive "r")
  (shell-command-on-region
   (or b (point-min))
   (or e (point-max))
   "/opt/local/bin/figlet" (current-buffer) t)
  (comment-region (mark) (point)))

但请注意b and e当此命令交互运行时将始终被设置。

你也可以这样做：

(require 'cl)

(defun* figlet-region (&optional (b (point-min)) (e (point-max)))
  # your original function body here
    )

EDIT:

所以我猜您的意思是即使该区域未处于活动状态，您也希望能够以交互方式运行该命令？那么也许这对你有用：

(defun figlet-region ()
  (interactive)
  (let ((b (if mark-active (min (point) (mark)) (point-min)))
        (e (if mark-active (max (point) (mark)) (point-max))))
    # ... rest of your original function body ...
      ))