From: IRIE Shinsuke <irieshinsuke@yahoo.co.jp>
Date: Wed, 13 Oct 2010 03:30:36 +0000 (-0700)
Subject: * lisp/subr.el (last): Make it faster.
X-Git-Tag: emacs-pretest-24.0.90~104^2~275^2~438^2~46^2~29
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=3574440031b0fc21c98c188a2fa15705381cbe24;p=emacs.git

* lisp/subr.el (last): Make it faster.

Fixes: debbugs:7174
---

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 08fee1b1df3..39b5f3c0137 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,7 @@
+2010-10-13  IRIE Shinsuke  <irieshinsuke@yahoo.co.jp>  (tiny change)
+
+	* subr.el (last): Make it faster.  (Bug#7174)
+
 2010-10-13  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>  (tiny change)
 
 	* Makefile.in (compile-clean): Use `` instead of $().  (Bug#7178)
diff --git a/lisp/subr.el b/lisp/subr.el
index 484340895be..0ed4ae62795 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -289,14 +289,11 @@ If LIST is nil, return nil.
 If N is non-nil, return the Nth-to-last link of LIST.
 If N is bigger than the length of LIST, return LIST."
   (if n
-      (let ((m 0) (p list))
-	(while (consp p)
-	  (setq m (1+ m) p (cdr p)))
-	(if (<= n 0) p
-	  (if (< n m) (nthcdr (- m n) list) list)))
-    (while (consp (cdr list))
-      (setq list (cdr list)))
-    list))
+      (and (> n 0)
+           (let ((m (length list)))
+             (if (< n m) (nthcdr (- m n) list) list)))
+    (and list
+         (nthcdr (1- (length list)) list))))
 
 (defun butlast (list &optional n)
   "Return a copy of LIST with the last N elements removed."