Are matrix commands broken?

[phario]

I'm unable to compile a document with this: 

<?xml version="1.0" encoding="UTF-8"?>
<chapter xml:id="ch-chapter00-introduction" xmlns:xi="http://www.w3.org/2001/XInclude">
  <title>Introduction</title>

  <introduction>
    <p> Text before the first section. </p>
  </introduction>

  <section xml:id="sec-Test">
    <title>Test</title>
    <p>
      <me>
        \begin{pmatrix}
        0 & 1 \\
        1 & 8
        \end{pmatrix}
      </me>
    </p>
  </section>

  <!-- include sections -->
  <!-- <xi:include href="sec-section-name.ptx" /> -->
</chapter>

But when I replace the pmatrix command with this (no ampersands): 

      <me>
        \begin{pmatrix}
        0 \\
        1 
        \end{pmatrix}
      </me>

It then compiles just fine. 

Can anyone comment on this issue? Seems very strange. Looking through documentation, it suggests that pmatrix should work with MathJax right out of the box.

[Mitch Keller]

& is a special character for XML. You need to use \amp anywhere you’d type & in math mode in LaTeX when writing PreTeXt. 

-- 

Mitch Keller

On Aug 26, 2025, at 07:05, phario <phil...@gmail.com> wrote:



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[Charilaos Skiadas]

Take a look at section 3.14 of the guide: https://pretextbook.org/doc/guide/html/overview-exceptional-characters.html

In short, the ampersand is a special character in XML and needs to be escaped and written as "&amp;”

  

Charilaos Skiadas
Department of Mathematics
Hanover College

[phario]

Hi,

Thanks for this. 

I guess Sec 3.14 is discussing the use of & in regular text mode. So I guess you should replace with &amp; Thanks!

Trying this in Math mode did not work; so then I understand Mitch Keller's advice that you need to use \amp

Reading the documentation more closely, I see it is mentioned in sec. 4.9.5

https://pretextbook.org/doc/guide/html/topic-mathematics.html

Thanks!