Re: Equation labels/references when converting from latex to markdown/other

[Leena Murgai <leenamurgai-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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Thanks for the reply John.

I've been playing around with an equation in LaTeX and seeing what comes 
out in HTML5 and also looking at what pandoc-crossref expects to find in 
the markdown. 

LaTeX equation format:
  \begin{equation} \label{eq:label}
  equation
  \end{equation}
Note: \label{eq:label} must be inside the equation environment, above is 
how I do it, but equally one can place the label after equation.

I tried moving label around in my LaTeX to see if it made a difference to 
the output HTML since pandoc-crossref expects to find the label after the 
equation environment 
<http://lierdakil.github.io/pandoc-crossref/#equation-labels>. Here's the 
HTML output in each case:

1. \label{eq:label} after \begin{equation}:

  <span class="math display">\label{eq:label}equation</span>

2. \label{eq:label} after equation:

  <span class="math display">equation\label{eq:label}</span>

3. \label{eq:label} after \end{equation}: Note that this will break the 
LaTeX code

  <span class="math display">equation</span><span>[eq:label]</span>

So, none of the above seem to give pandoc-crossref what it needs. Honestly, 
I'm not massively familiar with HTML and css - just figuring it out as I 
go. I imagine whatever pandoc-crossref would output (if I could get it to 
work) would be great. My quick and dirty approach (to get something like 
what LaTeX gives) would be to put the equation and its label in a table 
row. Something like

<div>
<table width=100% style="border: none;">
<tr>
<td style="text-align: center; border: none;"><span id="eq:label" 
class="math display">equation</span></td>
<td style="text-align: right; border: none; width: 5%;">(chap#.value{
eq:label})</td>
</tr>
</table>
</div>

I'm open to suggestions if hard coding 5% for the label width seems like a 
bad idea or some such.

Thanks,
Leena



On Wednesday, 21 July 2021 at 22:24:47 UTC-7 John MacFarlane wrote:

>
> As I said:
>
> Just let us know what you want to appear in the HTML, and we can
> show you how to do it.
>
>
>
> Leena Murgai <leena...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> writes:
>
> > Hi John,
> >
> > Can you clarify your work around here? I wasn't able to follow.
> >
> > I have a similar problem converting from LaTeX to HTML5 - \label and 
> \ref 
> > for equations don't work. I'd be super grateful for any advice you could 
> > offer.
> >
> > Thanks!
> > Leena
> >
> > On Tuesday, 29 June 2021 at 11:23:40 UTC-7 John MacFarlane wrote:
> >
> >>
> >> This isn't yet supported, really. But you might be able to
> >> work around it.
> >>
> >> Note:
> >>
> >> % pandoc -f latex -t native
> >> \ref{foo}
> >> ^D
> >> [Para [Link ("",[],[("reference-type","ref"),("reference","foo")]) [Str 
> >> "[foo]"] ("#foo","")]]
> >>
> >> So when pandoc parses \ref{foo}, it doesn't just create a string
> >> [foo]; it creates a link with attributes. You could use a lua
> >> filter to turn this into something that mathjax can consume
> >> (raw tex, I would imagine).
> >>
> >> Just let us know what you want to appear in the HTML, and we can
> >> show you how to do it.
> >>
> >> Ian Price <ianpr...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> writes:
> >>
> >> > Hello,
> >> > My university is looking into the options for converting various 
> notes, 
> >> > exercises sheets, presentations, etc. from latex generated pdf into a 
> >> more 
> >> > accessible format. This basically means converting to html + mathjax 
> >> > because this tends to work better for screen readers. Converting 
> beamer 
> >> > seems to be impossible, but for notes pandoc (and some others like 
> >> latexml) 
> >> > is generally giving good output, however the major issue is cross 
> >> > referencing between text and maths blocks.
> >> >
> >> > In short, mathjax can handle internal links from maths blocks to 
> other 
> >> > maths blocks, and pandoc can handle links to other parts of pandoc 
> >> > documents, except when a document makes specific reference to an 
> >> equation.
> >> > For example, suppose we have the following mwe.tex cut out from some 
> >> > electromagnetism notes
> >> > ---
> >> > \documentclass[12pt]{article} 
> >> > \begin{document} 
> >> > \begin{equation} 
> >> > J \equiv \frac{dI}{da_{\perp}} = \rho v. 
> >> > \label{volume-current-density} 
> >> > \end{equation} 
> >> > The total current crossing a surface $S$ can be calculated by 
> >> integrating 
> >> > Eq. (\ref{volume-current-density}): 
> >> > \end{document}
> >> > ---
> >> > When converted to markdown, we get the following
> >> > ---
> >> > $$J \equiv \frac{dI}{da_{\perp}} = \rho v. 
> >> > \label{volume-current-density}$$ 
> >> > 
> >> > The total current crossing a surface $S$ can be calculated by 
> >> > integrating Eq. 
> >> > 
> >> 
> ([\[volume-current-density\]](#volume-current-density){reference-type="ref" 
> >> > reference="volume-current-density"}):
> >> > ---
> >> > The link to the label volume-current-density is clearly broken and 
> when 
> >> I 
> >> > get my html file it does nothing in particular.
> >> >
> >> > One solution I've seen is to convert the label references to the 
> syntax 
> >> > used by, e.g., pandoc-crossref, but this involves me editing the 
> >> markdown 
> >> > by hand. Is there an automatic way to convert these? 
> >> >
> >> > -- 
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> >> 
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> >>
> >
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