(defun wg-next-buffer-internal (buffer-list &optional prev noerror)

  "Switch to the next buffer in Workgroups' filtered buffer list."

  (when buffer-list

    (let* ((cur (current-buffer))

           (next (or (wg-cyclic-nth-from-elt cur buffer-list (if prev -1 1))

                     (car buffer-list))))

      (unless (eq cur next)

        (switch-to-buffer next)

        (unless prev (bury-buffer cur))

        next))))

(defun wg-next-buffer (&optional prev)

  "Switch to the next buffer in Workgroups' filtered buffer list.

In the post-command message the current buffer is rotated to the

middle of the list to more easily see where `wg-previous-buffer'

will take you."

  (interactive)

  (let ((command (if prev 'previous-buffer 'next-buffer)))

    (if (not (wg-filter-buffer-list-p))

        (call-interactively (wg-prior-mapping workgroups-mode command))

      (wg-with-buffer-list-filters command

        (awhen (wg-filtered-buffer-list) (wg-next-buffer-internal it prev))

        (wg-message (wg-buffer-command-display))))))

(defun wg-rnth (n list)

  "Return the Nth element of LIST, counting from the end."

  (nth (- (length list) n 1) list))

(defun wg-take-until-fail (pred list)

  "Take elements from LIST up to the first element on which PRED fails."

  (let (taken)

    (catch 'result

      (dolist (elt list (nreverse taken))

        (if (funcall pred elt) (push elt taken)

          (throw 'result (nreverse taken)))))))