add space between Chinese and Englisth letters

article_format.el

(defun ifree--format-article (begin end)
  "Add space between Chinese and English letters between BEGIN and END."
  (interactive "r")
  (let (region-begin
        region-end
        (matcher-begin "\\(?1:[\u4e00-\u9fa5]+\\)\\(?2:[a-zA-Z]+\\)")  ;cjk,
                                                                       ;symbols?
        (matcher-end "\\(?1:[a-zA-Z]+\\)\\(?2:[\u4e00-\u9fa5]+\\)"))
    
    (if (region-active-p)
        (setq region-begin begin region-end end)
      (setq region-begin (point-min) region-end (point-max)))
    
    (save-excursion
      (goto-char region-begin)
      (while (re-search-forward matcher-begin region-end t)
        (replace-match "\\1 \\2")
        (setq region-end (+ 1 region-end)))
      (goto-char region-end)
      (while (re-search-backward matcher-end region-begin t)
        (replace-match "\\1 \\2")))))