(defun-maybe-cond): New macro.

(next-command-event): Use `defun-maybe-cond'.
(cancel-undo-boundary): Use `defun-maybe-cond'.

diff --git a/poe.el b/poe.el
index 90a0571..fb56d9e 100644 (file)
--- a/poe.el
+++ b/poe.el
@@ -95,6 +95,27 @@
               ))
         )))
 
+(defmacro defun-maybe-cond (name args &optional doc &rest everything-else)
+  (unless (stringp doc)
+    (setq everything-else (cons doc everything-else)
+         doc nil)
+    )
+  (or (and (fboundp name)
+          (not (get name 'defun-maybe)))
+      (` (unless (fboundp (quote (, name)))
+          (cond (,@ (mapcar (lambda (case)
+                              (list (car case)
+                                    (if doc
+                                        (` (defun (, name) (, args)
+                                             (, doc)
+                                             (,@ (cdr case))))
+                                      (` (defun (, name) (, args)
+                                           (,@ (cdr case))))
+                                      )))
+                            everything-else)))
+          (put (quote (, name)) 'defun-maybe t)
+          ))))
+
 (defsubst subr-fboundp (symbol)
   "Return t if SYMBOL's function definition is a built-in function."
   (and (fboundp symbol)
@@ -477,33 +498,23 @@ as obsolete. [XEmacs emulating function]"
 
 (when (subr-fboundp 'read-event)
   ;; for Emacs 19 or later
-  (cond
-   ((subr-fboundp 'string)
-    ;; for Emacs 20.3 or later
-    (defun-maybe next-command-event (&optional event prompt)
-      "Read an event object from the input stream.
-If EVENT is non-nil, it should be an event object and will be filled
-in and returned; otherwise a new event object will be created and
-returned.
-If PROMPT is non-nil, it should be a string and will be displayed in
-the echo area while this function is waiting for an event.
-\[XEmacs emulating function]"
-      (read-event prompt t)
-      )
-    )
-   (t
-    (defun-maybe next-command-event (&optional event prompt)
-      "Read an event object from the input stream.
+
+  (defun-maybe-cond next-command-event (&optional event prompt)
+    "Read an event object from the input stream.
 If EVENT is non-nil, it should be an event object and will be filled
 in and returned; otherwise a new event object will be created and
 returned.
 If PROMPT is non-nil, it should be a string and will be displayed in
 the echo area while this function is waiting for an event.
 \[XEmacs emulating function]"
-      (message prompt)
-      (read-event)
-      )
-    ))
+    ((subr-fboundp 'string)
+     ;; for Emacs 20.3 or later
+     (read-event prompt t)
+     )
+    (t
+     (if prompt (message prompt))
+     (read-event)
+     ))
 
   (defsubst-maybe character-to-event (ch)
     "Convert keystroke CH into an event structure, replete with bucky bits.
@@ -531,19 +542,18 @@ If the event isn't a keypress, this returns nil.
 ;;; @ MULE 2 emulation
 ;;;
 
-(if (boundp 'buffer-undo-list)
-    ;; for Emacs 19.7 or later
-    (defun-maybe cancel-undo-boundary ()
-      "Cancel undo boundary. [MULE 2.3 emulating function]"
-      (if (and (consp buffer-undo-list)
-              ;; if car is nil.
-              (null (car buffer-undo-list)))
-         (setq buffer-undo-list (cdr buffer-undo-list))
-       ))
-  ;; for anything older than Emacs 19.7.    
-  (defun-maybe cancel-undo-boundary ()
-    "Cancel undo boundary. [MULE 2.3 emulating function]")
-  )
+(defun-maybe-cond cancel-undo-boundary ()
+  "Cancel undo boundary. [MULE 2.3 emulating function]"
+  ((boundp 'buffer-undo-list)
+   ;; for Emacs 19.7 or later
+   (if (and (consp buffer-undo-list)
+           ;; if car is nil.
+           (null (car buffer-undo-list)))
+       (setq buffer-undo-list (cdr buffer-undo-list))
+     ))
+  (t
+   ;; for anything older than Emacs 19.7.    
+   ))
 
 
 ;;; @ end