From: Paul Eggert <eggert@cs.ucla.edu>
Date: Mon, 18 Feb 2019 22:51:26 +0000 (-0800)
Subject: Speed up cl-list-length
X-Git-Tag: archive/raspbian/1%29.2+1-2+rpi1^2~5^2~19^2~3970
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=a812ed215ce0a7a53f51dd5aa51de720917d2ff0;p=emacs.git

Speed up cl-list-length

* lisp/emacs-lisp/cl-extra.el (cl-list-length): Use ‘length’
to do the real work; this is simpler and uses a better algorithm.
---

diff --git a/lisp/emacs-lisp/cl-extra.el b/lisp/emacs-lisp/cl-extra.el
index 99b55ad6b72..a2400a0ba37 100644
--- a/lisp/emacs-lisp/cl-extra.el
+++ b/lisp/emacs-lisp/cl-extra.el
@@ -594,10 +594,10 @@ too large if positive or too small if negative)."
 ;;;###autoload
 (defun cl-list-length (x)
   "Return the length of list X.  Return nil if list is circular."
-  (let ((n 0) (fast x) (slow x))
-    (while (and (cdr fast) (not (and (eq fast slow) (> n 0))))
-      (setq n (+ n 2) fast (cdr (cdr fast)) slow (cdr slow)))
-    (if fast (if (cdr fast) nil (1+ n)) n)))
+  (cl-check-type x list)
+  (condition-case nil
+      (length x)
+    (circular-list)))
 
 ;;;###autoload
 (defun cl-tailp (sublist list)