Ihor Radchenko <yantar92@posteo.net> writes:

> Is it really recommended by mathjax?

Yes.

> I cannot find any mention of jsdelivr.com.

1. Open MathJax docs (https://docs.mathjax.org/en/latest/).
2. Type "jsDelivr" into the search box.
3. Check the search results.

> You may update the URL to something more precise.

Fixed.

> Are these extensions no longer supported?

MathJax 3+ supports extensions, and one can load them in multiple ways.
See [1].  It deserves some thinking, for the extensions mirror LaTeX
extensions.  So, to make both HTML and PDF work, one has:

  Use the Physics package in both LaTeX and MathJax.

  #+latex_header: \usepackage{physics}
  
  #+html_head_extra: <div style="display: none">
  #+html_head_extra:   \(
  #+html_head_extra:     \require{physics}
  #+html_head_extra:   \)
  #+html_head_extra: </div>

(The example taken from my Org notebook.)

[1]: https://docs.mathjax.org/en/latest/input/tex/extensions.html

That said, I do not currently have bandwidth to extend the scope of the
patch to include MathJax extensions.  (Note that they have never worked
anyway, so the user loses nothing, and we correct documentation.)

A slight digression, just FYI:

I realized that I should have improved LaTeX to SVG exports instead of
focusing on MathJax.  Org supports LaTeX environments, but outside of
PDFs, it does so poorly.  Packages such as TikZ, for example, do not
work out of the box, so people use Babel to hack around it.  Worse
still, Org does not even properly adjust baselines for inline math, so
HTML exports remain barely usable for any mathematical work.

If we fix LaTeX, Org could have fast and good mathematics, with no
JavaScript, like Wikipedia has.  Then, we could use it by default,
instead of MathJax.

Having good support for LaTeX would position Org as the king of markup
editors, because LaTeX can do everything under the sun.  For instance,
one can typeset a chess game in a couple of lines.  Or sheet music.  Or
molecules in three dimensions.  No mainstream Markdown editor or web
authoring tool can do that.  Yet, Org can *almost* do it.

> It would be more compact to use `(...) notation.

Fixed.

> nreverse will be more memory-efficient.

Fixed and TIL.

> Mostly because supporting MathJax 2 is an extra maintenance burden.  I
> do not see much point catering bugs of MathJax2 -> MathJax3
> conversion. If users want to use MathJax2 specifically, they should be
> able to customize Org to use MathJax2. If they want MathJax3, they
> need to fix the options. Relying on auto-conversion is calling for
> trouble.

Fixed.

Please see the 6th version of the patch, attached below.

P.S. I also replaced two subsequent `setq' calls with one.

Rudy