(mapc): Add the compiler macro for Emacs 20.

[gnus] / lisp / dgnushack.el

diff --git a/lisp/dgnushack.el b/lisp/dgnushack.el
index dc88a22..b505717 100644 (file)
--- a/lisp/dgnushack.el
+++ b/lisp/dgnushack.el
@@ -78,7 +78,24 @@
   (define-compiler-macro remove (&whole form item seq)
     (if (>= emacs-major-version 21)
        form
-      `(delete ,item (copy-sequence ,seq)))))
+      `(delete ,item (copy-sequence ,seq))))
+
+  (define-compiler-macro mapc (&whole form fn seq &rest rest)
+    (if (>= emacs-major-version 21)
+       form
+      (if rest
+         `(let* ((fn ,fn)
+                 (seq ,seq)
+                 (args (list seq ,@rest))
+                 (m (apply (function min) (mapcar (function length) args)))
+                 (n 0))
+            (while (< n m)
+              (apply fn (mapcar (function (lambda (arg) (nth n arg))) args))
+              (setq n (1+ n)))
+            seq)
+       `(let ((seq ,seq))
+          (mapcar ,fn seq)
+          seq)))))
 
 ;; If we are building w3 in a different directory than the source
 ;; directory, we must read *.el from source directory and write *.elc