Simplify rng-substq with cl-substitute

* lisp/nxml/rng-util.el (rng-substq): Simplify.
(cl-lib): Require.

1 files changed, 3 insertions, 20 deletions

diff --git a/lisp/nxml/rng-util.el b/lisp/nxml/rng-util.el
index 27c924d960f..4f49885fc45 100644
--- a/lisp/nxml/rng-util.el
+++ b/lisp/nxml/rng-util.el
@@ -24,6 +24,8 @@
 
 ;;; Code:
 
+(require 'cl-lib)
+
 (defun rng-make-datatypes-uri (uri)
   (if (string-equal uri "")
       ;; The spec doesn't say to do this, but it's perfectly conformant
@@ -39,26 +41,7 @@
 (defun rng-substq (new old list)
   "Replace first member of LIST (if any) that is `eq' to OLD by NEW.
 LIST is not modified."
-  (cond ((null list) nil)
-        ((eq (car list) old)
-         (cons new (cdr list)))
-        (t
-         (let ((tail (cons (car list)
-                           nil))
-               (rest (cdr list)))
-           (setq list tail)
-           (while rest
-             (let ((item (car rest)))
-               (setq rest (cdr rest))
-               (cond ((eq item old)
-                      (setcdr tail
-                              (cons new rest))
-                      (setq rest nil))
-                     (t
-                      (setq tail
-                            (setcdr tail
-                                    (cons item nil))))))))
-         list)))
+  (cl-substitute new old list :count 1 :test #'eq))
 
 (defun rng-escape-string (s)
   (replace-regexp-in-string "[&\"<>]"