From: Richard M. Stallman <rms@gnu.org>
Date: Thu, 13 Oct 1994 06:34:09 +0000 (+0000)
Subject: (add-to-list): New function.
X-Git-Tag: emacs-19.34~6344
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=6e3af6305a07eda134fde4c61cd59e0b6f41c96d;p=emacs.git

(add-to-list): New function.
---

diff --git a/lisp/subr.el b/lisp/subr.el
index 3c4308bf8c2..7c0ae0cb914 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -710,6 +710,11 @@ To make a hook variable buffer-local, always use
 	  (if (equal hook-value function)
 	      (setq hook-value nil)))
 	(set-default hook hook-value)))))
+
+(defun add-to-list (list-var element)
+  "Add to the value of LIST-VAR the element ELEMENT if it isn't there yet."
+  (or (member element (symbol-value list-var))
+      (set list-var (cons element (symbol-value list-var)))))
 
 ;;;; Specifying things to do after certain files are loaded.