Improving the support of LaTeX equations in Typst output

[oliviermeslin]

Description

TL;DR: I wonder whether it would be possible to include the mitex Typst package in Quarto (or in Pandoc) to make it easier to produce a website and a Typst pdf from the same Quarto files.

---

Context

I'm working on a Quarto project, and I'd like to produce two outputs: a website and a pdf produced by Typst. There are many equations in this project, written using the LaTeX syntax. I can easily include them in the Typst document using the mitex package, but then the qmd files cannot be used directly to produce the website. Some workarounds using when-format might be possible, but they would be detrimental to the readibility of the qmd files and would likely result in code duplication.

Here is a MWE of my current source code for the Typst output:

---
format: typst
---

```{=typst}
#import "@preview/mitex:0.2.4": *
```

This a Typst document with a simple inline LaTeX equation (`#mi("$\hat{F}$")`{=typst}) and a complicated LaTeX block equation:

```{=typst}
#mitex(`
$\begin{align*}
\mathcal{\tilde{L}}^{(k)}
&= \sum_{j=1}^{T} \sum_{i\in I_j} \Bigl[g_i f_k(\mathbf{x}_i) &+ \frac{1}{2} h_i f^2_k(\mathbf{x}_i)\Bigr] &+ \gamma T + \frac{1}{2} \lambda \sum_{j=1}^T w_j^2 \\
&= \sum_{j=1}^{T} \sum_{i\in I_j} \Bigl[g_i w_j &+ \frac{1}{2} h_i w_j^2\Bigl] &+ \gamma T + \frac{1}{2} \lambda \sum_{j=1}^T w_j^2 \\
&= \sum^T_{j=1} \Bigl[w_j\Bigl(\sum_{i\in I_j} g_i\Bigr) &+ \frac{1}{2} w_j^2 \Bigl(\sum_{i\in I_j} h_i + \lambda\Bigr) \Bigr] &+ \gamma T  \label{eq:dudu}
\end{align*}$
  `)
```

Feature request

I would like to produce a Typst document with LaTeX-style equations without having to encapsulate them explicitly in the proper #mitex() or #mi() environments in the qmd files. This way, the same qmd files could be used to produce the pdf and the website.

Based on this discussion, I think that a solution could consist in adding a Lua filter in the Quarto Typst support (or in Pandoc), so that LaTeX-style equations would invisibly be encapsulated using mitex when output format is Typst. Maybe this feature request concerns Pandoc more than Quarto, let me know if you think so.

[mcanouil]

You should be able to do that with a LUA filter targeting equation in the AST.

Note that adding a dependency is not something to be done lightly especially from a project that is very young (Typst).

Edit: see @cderv's comment with an experimental extension showing the above idea: #11075 (comment)

[cderv]

I wanted to see how easy it would be to integrate with mitex using an extension. Here is an experiment you can use and contribute to improve

• https://github.com/quarto-ext/mitex

[oliviermeslin]

Thanks @cderv ! I'll definitely have a look at this extension!

By the way, I had already started writing a Lua filter that encapsulates equations in the proper mitex environments.