[XeTeX] Xetex, Latex3, unicode-math and Math font not found

[Phelype Oleinik]

On Wed, May 13, 2020 at 10:22 AM Pierre Dupond <76nemo76 at gmx.ch> wrote:
>
> > \exp_args:Nxx \setmathfont
> >   { \tl_use:N \c__test_MathFont_tl }
> >   { [ \tl_use:N \c__test_MathFontSpec_tl ] }
> >
> Thanks for the explanations but this form does not work.

Sorry, my mistake. The three lines above expand to

    \setmathfont{Asana-Math}{[Extension=.otf,]}

which is wrong because the optional argument is not seen.  In this case
you'd need `\exp_last_unbraced:Nxx`, which can be defined as

    \cs_gset_protected:Npn \exp_last_unbraced:Nxx { \::x \::x_unbraced \::: }

but this interface should be used sparingly, so the `\use:x` version is
better.

Phelype