我无法直接回答您的问题,但我使用的一种技术是检查functionp
告诉我函数是否存在的函数。
例如
(if (load "completion" t)
(progn
(initialize-completions)
(if (functionp 'dynamic-completion-mode)
(dynamic-completion-mode) ; if exists
(completion-mode) ; otherwise use old version
)
) ; progn
) ; if
更新:添加特定于版本的宏
除了使用之外,functionp
我还有一些特定于版本的宏:
(defmacro GNU_EMACS_21 (&rest stuff)
(list 'if (string-match "GNU Emacs 21" (emacs-version)) (cons 'progn stuff)))
(defmacro GNU_EMACS_20 (&rest stuff)
(list 'if (string-match "GNU Emacs 20" (emacs-version)) (cons 'progn stuff)))
(defmacro GNU_EMACS_19 (&rest stuff)
(list 'if (string-match "GNU Emacs 19" (emacs-version)) (cons 'progn stuff)))
(defmacro WINSYS_X (&rest stuff)
(list 'if (eq window-system 'x) (cons 'progn stuff)))
(defmacro WINSYS_W32 (&rest stuff)
(list 'if (eq window-system 'w32) (cons 'progn stuff)))
(defmacro WINSYS_NIL (&rest stuff)
(list 'if (eq window-system nil) (cons 'progn stuff)))
(defmacro SYSTYPE_LINUX (&rest stuff)
(list 'if (string-match "linux" (symbol-name system-type)) (cons 'progn stuff)))
然后我可以使用这些:
(GNU_EMACS_21
(if (load "cua" t)
(CUA-mode t)
)
)
(WINSYS_NIL ; when running in text mode
(push (cons 'foreground-color "white") default-frame-alist)
(push (cons 'background-color "black") default-frame-alist)
(push (cons 'cursor-color "cyan") default-frame-alist)
(push (cons 'minibuffer t) default-frame-alist)
)
但是,我猜您已经知道了;像“Emacs 何时包含 CUA 模式”这样的问题很难回答。