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const xah_range = ( min, max, step = 1, ) => (Array(Math.floor((max - min) / step) + 1).fill(min).map(( x, i, ) => (x + i * step)));

/* return the hexadecimal string of the char's utf16 encoding.
string is separated by space for each char
 */
const f_charID_to_utf16_hexStr = (CharID: number): string => {
  const xCharStr = String.fromCodePoint(CharID)
  if (CharID < 2 ** 16) {
    return xCharStr.charCodeAt(0).toString(16).toUpperCase()
  } else {
    const xLen = String.fromCodePoint(CharID).length
    const xResultArray = []
    for (let i = 0; i < xLen; i++) {
      xResultArray.push(xCharStr.charCodeAt(i).toString(16).toUpperCase())
    }
    return xResultArray.join(" ")
  }
}

(defun xah-upcase-sentence ()
  "Upcase first letters of sentences of current block or selection.

URL `http://xahlee.info/emacs/emacs/emacs_upcase_sentence.html'
Created: 2020-12-08
Version: 2025-03-25"
  (interactive)
  (let (xbeg xend)
    (seq-setq (xbeg xend) (if (region-active-p) (list (region-beginning) (region-end)) (list (save-excursion (if (re-search-backward "\n[ \t]*\n" nil 1) (match-end 0) (point))) (save-excursion (if (re-search-forward "\n[ \t]*\n" nil 1) (match-beginning 0) (point))))))
    (save-restriction
      (narrow-to-region xbeg xend)
      (let ((case-fold-search nil))
        ;; after period or question mark or exclamation
        (goto-char (point-min))
        (while (re-search-forward "\\(\\.\\|\\?\\|!\\)[ \n]+ *\\([a-z]\\)" nil 1)
          (upcase-region (match-beginning 2) (match-end 2))
          (overlay-put (make-overlay (match-beginning 2) (match-end 2)) 'face 'highlight))
        ;; after a blank line, after a bullet, or beginning of buffer
        (goto-char (point-min))
        (while (re-search-forward "\\(\\`\\|• \\|\n\n\\)\\([a-z]\\)" nil 1)
          (upcase-region (match-beginning 2) (match-end 2))
          (overlay-put (make-overlay (match-beginning 2) (match-end 2)) 'face 'highlight))
        ;; for HTML. first letter after tag
        (when
            (or
             (eq major-mode 'xah-html-mode)
             (eq major-mode 'html-mode)
             (eq major-mode 'sgml-mode)
             (eq major-mode 'nxml-mode)
             (eq major-mode 'xml-mode)
             (eq major-mode 'mhtml-mode))
          (goto-char (point-min))
          (while
              (re-search-forward "\\(<title>[ \n]?\\|<h[1-6]>[ \n]?\\|<p>[ \n]?\\|<li>[ \n]?\\|<dd>[ \n]?\\|<td>[ \n]?\\|<br ?/?>[ \n]?\\|<figcaption>[ \n]?\\)\\([a-z]\\)" nil 1)
            (upcase-region (match-beginning 2) (match-end 2))
            (overlay-put (make-overlay (match-beginning 2) (match-end 2)) 'face 'highlight))))
      (goto-char (point-max)))
    (skip-chars-forward " \n\t")))