static new ThreadLocal<Int> ai_tokenizationToTextPane_charsWritten;

static JTextPane ai_tokenizationToTextPane(LS tok) {
  ret ai_tokenizationToTextPane(fontSizePlus(7, jtextpane()), tok);
}

static JTextPane ai_tokenizationToTextPane(JTextPane tp, LS tok) {
  bool spaced = true;
  int chars = 0;
  for i over tok: {
    if (!spaced) {
      appendToTextPane(tp, " ");
      ++chars;
      spaced = true;
    }
    S t = tok.get(i);
    if (empty(t)) continue;
    SimpleAttributeSet style;
    if (odd(i)) // C token
      style = style_background(Color.yellow, style_foreground(Color.black));
    else // N token (whitespace)
      style = style_foreground(Color.gray, style_background(colorFromHex("#E0E0E0")));
    appendToTextPane(tp, t, style);
    chars += l(t);
    spaced = false;
  }
  setTL(ai_tokenizationToTextPane_charsWritten, chars);
  ret tp;
}