[Emacs[Lisp][Meadow] An Introduction to Programming in Emacs Lisp Chapter 06

オレ，前回 Exercise を間違えてた。Chapter06 の Exercise だった。orz

Chapter 06

• save-restriction
  • special-form
  • narrowingされていればその状態を保存
  • bodyを実行
  • 保存しておいたnarrowingを復旧

Exercise 5.5

というわけで，Chapter06 の Exercise は Chapter05 の方に書いてしまったので，
こちらでは，Chapter05 の Exercise をば。

;;; Exercise 5.5
(defun my-greater-or-less (&optional arg)
  "Tell whether ARG is greater or less than fill-column."
  (interactive "P")
  (let (num)
    (if arg (setq num (prefix-numeric-value arg))
      (setq num 56))
    (cond ((> num fill-column)
           (message "%d is greater than fill-column(%d)" num fill-column))
          ((< num fill-column)
           (message "%d is less than fill-column(%d)" num fill-column))
          (t (message "%d is equal to fill-column(%d)" num fill-column)))))
;; お試し
(my-greater-or-less 10)
; => "10 is less than fill-column(70)"
(my-greater-or-less 70)
; => "70 is equal to fill-column(70)"
(my-greater-or-less 71)
; => "71 is greater than fill-column(70)"

おつかれちゃん。