Prefer seq-random-elt to nth+random

* lisp/emacs-lisp/seq.el (seq-random-elt): Autoload.
* lisp/avoid.el (mouse-avoidance-random-shape):
* lisp/epa-ks.el (epa-ks--query-url):
* lisp/erc/erc-networks.el (erc-server-select):
* lisp/gnus/gnus-fun.el (gnus--random-face-with-type)
(gnus-fun-ppm-change-string):
* lisp/net/soap-inspect.el (soap-sample-value-for-xs-simple-type):
* lisp/obsolete/landmark.el (landmark-random-move):
* lisp/play/mpuz.el (mpuz-build-random-perm):
* lisp/play/zone.el (zone-pgm-stress):
* lisp/vc/add-log.el (add-change-log-entry):
* test/lisp/net/tramp-tests.el
(tramp-test44-asynchronous-requests): Prefer seq-random-elt to
nth+random.

lisp/avoid.el

@@ -43,7 +43,7 @@
 ;;
 ;; (if (eq window-system 'x)
 ;;     (mouse-avoidance-set-pointer-shape
-;;	     (nth (random 4)
+;;	     (seq-random-elt
 ;;		  (list x-pointer-man x-pointer-spider
 ;;			x-pointer-gobbler x-pointer-gumby))))
 ;;
@@ -125,7 +125,6 @@ TOP-OR-BOTTOM-POS: Distance from top or bottom edge of frame or window."
 ;; Internal variables
 (defvar mouse-avoidance-state nil)
 (defvar mouse-avoidance-pointer-shapes nil)
-(defvar mouse-avoidance-n-pointer-shapes 0)
 (defvar mouse-avoidance-old-pointer-shape nil)
 (defvar mouse-avoidance-animating-pointer nil)
 
@@ -306,11 +305,8 @@ redefine this function to suit your own tastes."
 		      (all-completions "x-pointer-" obarray
 				       (lambda (x)
 					  (and (boundp x)
-					       (integerp (symbol-value x)))))))
+                                               (integerp (symbol-value x)))))))))
-	(setq mouse-avoidance-n-pointer-shapes
+  (seq-random-elt mouse-avoidance-pointer-shapes))
-	      (length mouse-avoidance-pointer-shapes))))
-  (nth (random mouse-avoidance-n-pointer-shapes)
-       mouse-avoidance-pointer-shapes))
 
 (defun mouse-avoidance-ignore-p ()
   (let ((mp (mouse-position)))

lisp/emacs-lisp/seq.el

@@ -570,6 +570,7 @@ SEQUENCE must be a sequence of numbers or markers."
 If no element is found, return nil."
   (ignore-errors (seq-elt sequence n)))
 
+;;;###autoload
 (cl-defgeneric seq-random-elt (sequence)
   "Return a random element from SEQUENCE.
 Signal an error if SEQUENCE is empty."

lisp/epa-ks.el

@@ -149,8 +149,7 @@ If EXACT is non-nil, don't accept approximate matches."
           (cond ((null epa-keyserver)
                  (user-error "Empty keyserver pool"))
                 ((listp epa-keyserver)
-                 (nth (random (length epa-keyserver))
+                 (seq-random-elt epa-keyserver))
-                      epa-keyserver))
                 ((stringp epa-keyserver)
                  epa-keyserver)
                 ((error "Invalid type for `epa-keyserver'")))

lisp/erc/erc-networks.el

@@ -824,7 +824,7 @@ As an example:
 	 (ports (if (listp (nth 3 srv))
 		    (erc-ports-list (nth 3 srv))
 		  (list (nth 3 srv))))
-	 (port (nth (random (length ports)) ports)))
+         (port (and ports (seq-random-elt ports))))
     (erc :server host :port port)))
 
 ;;; The following experimental

lisp/gnus/gnus-fun.el

@@ -103,7 +103,7 @@ PNG format."
             (remove nil (mapcar
                          (lambda (f) (unless (string-match (or omit "^$") f) f))
                          (directory-files dir t ext))))
-           (file (nth (random (length files)) files)))
+           (file (and files (seq-random-elt files))))
       (when file
         (funcall fun file)))))
 
@@ -315,7 +315,7 @@ colors of the displayed X-Faces."
   (let* ((possibilities '("%02x0000" "00%02x00" "0000%02x"
 			  "%02x%02x00" "00%02x%02x" "%02x00%02x"))
 	 (format (concat "'#%02x%02x%02x' '#"
-			 (nth (random 6) possibilities)
+                         (seq-random-elt possibilities)
 			 "'"))
 	 (values nil))
   (dotimes (i 255)

lisp/net/soap-inspect.el

@@ -114,7 +114,7 @@ This is a specialization of `soap-sample-value' for
    (cond
     ((soap-xs-simple-type-enumeration type)
      (let ((enumeration (soap-xs-simple-type-enumeration type)))
-       (nth (random (length enumeration)) enumeration)))
+       (and enumeration (seq-random-elt enumeration))))
     ((soap-xs-simple-type-pattern type)
      (format "a string matching %s" (soap-xs-simple-type-pattern type)))
     ((soap-xs-simple-type-length-range type)
@@ -134,7 +134,7 @@ This is a specialization of `soap-sample-value' for
         (t (random 100)))))
     ((consp (soap-xs-simple-type-base type)) ; an union of values
      (let ((base (soap-xs-simple-type-base type)))
-       (soap-sample-value (nth (random (length base)) base))))
+       (soap-sample-value (and base (seq-random-elt base)))))
     ((soap-xs-basic-type-p (soap-xs-simple-type-base type))
      (soap-sample-value (soap-xs-simple-type-base type))))))
 

lisp/obsolete/landmark.el

@@ -1470,7 +1470,7 @@ push him out of it."
   (mapc
    (lambda (direction) (put direction 'y_t 0))
    landmark-directions)
-  (dolist (direction (nth (random 8) landmark-8-directions))
+  (dolist (direction (seq-random-elt landmark-8-directions))
     (put direction 'y_t 1.0))
   (landmark-move))
 

lisp/play/mpuz.el

@@ -153,7 +153,7 @@ You may abort a game by typing \\<mpuz-mode-map>\\[mpuz-offer-abort]."
 	(index 10)
 	elem)
     (while letters
-      (setq elem    (nth (random index) letters)
+      (setq elem    (seq-random-elt letters)
 	    letters (delq elem letters)
 	    index   (1- index))
       (aset mpuz-digit-to-letter index elem)

lisp/play/zone.el

@@ -596,7 +596,7 @@ If the element is a function or a list of a function and a number,
          (forward-line -1)
          (delete-region (point) (line-beginning-position 2))
          (goto-char (point-min))
-         (insert (nth (random (length lines)) lines)))
+         (insert (seq-random-elt lines)))
        (message (concat (make-string (random (- (frame-width) 5)) ? ) "grrr"))
        (sit-for 0.1)))))
 

lisp/vc/add-log.el

@@ -930,8 +930,7 @@ non-nil, otherwise in local time."
 			    (not (looking-at "[ \t]+.*<.*>$")))
 			  (setq hit t)))))
             (forward-line 1)
-          (insert (nth (random (length new-entries))
+          (insert (and new-entries (seq-random-elt new-entries))
-                       new-entries)
                   (if use-hard-newlines hard-newline "\n")
                   (if use-hard-newlines hard-newline "\n"))
           (forward-line -1))))

test/lisp/net/tramp-tests.el

@@ -6787,8 +6787,7 @@ process sentinels.  They shall not disturb each other."
                     (let ((time (float-time))
                           (default-directory tmp-name)
                           (file
-                           (buffer-name
+                           (buffer-name (seq-random-elt buffers)))
-                            (nth (random (length buffers)) buffers)))
 			  ;; A remote operation in a timer could
 			  ;; confuse Tramp heavily.  So we ignore this
 			  ;; error here.
@@ -6853,7 +6852,7 @@ process sentinels.  They shall not disturb each other."
             ;; the buffers.  Mix with regular operation.
             (let ((buffers (copy-sequence buffers)))
               (while buffers
-                (let* ((buf (nth (random (length buffers)) buffers))
+                (let* ((buf (seq-random-elt buffers))
                        (proc (get-buffer-process buf))
                        (file (process-get proc 'foo))
                        (count (process-get proc 'bar)))