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

Fixes: debbugs:7174

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 08fee1b1df3c46f645c672a292ca305c974c7e39..39b5f3c0137aa0077caebe73d4d9658d4c8d8a83 100644 (file)
--- 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 484340895be42bd6e6c3f1a5b679fdf6daf3b284..0ed4ae62795fa0d1bc841efe1eb736aca0d21467 100644 (file)
--- 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."