# [tex4ht] exerquiz problems

Tomas Davidek Tomas.Davidek at cern.ch
Thu Jan 21 07:47:17 CET 2021

Thanks a lot, Michal, this helped a lot. I am usually running several
checks on the LaTeX code, but both pdflatex and lacheck did not reveal
this problem.

Cheers,

Tomas

On 1/19/21 11:10 PM, Michal Hoftich wrote:
> Dear Tomáš,
>
>
>> Well, the error message suggests there might be a problem in the
>> configuration file (split.cfg), but - when getting rid of the
>> exerquiz environment, the error message disappears. It's strange,
>> maybe there is some interference between the align and example
>> environments?? I don't know.
>>
>> Attached is a tarball containing all files needed for running the
>> example. The examples are two - one with the exercise environment
>> heavily used (exerquiz_exx.tex) and another without using this
>> environment (exerquiz_ex.tex, this one runs ok).
>
> In this particular example, exerquiz_exx.tex, I've found a following
> issue:
>
>
> Vztah~(\ref{eq:cross_section_annihilation}) dává číselnou hodnotu
> \begin{displaymath}
>   \label{eq:cross_section_value}
>   \sigma
> =\frac{4\pi\left(\frac{1}{137}\right)^2\left(0{,}197~\gev\cdot\mathrm{fm}\right)^2}{3s}
>   \doteq 8{,}66\cdot 10^{-6}\frac{1}{s~[\gev^2]}~\mathrm{fm}^2
>   % = 2{,}232\cdot 10^{-5}~\gev^{-2} = \\
>   % & = 2{,}232\cdot 10^{-5}\times 0{,}197^2~\mathrm{fm}^2 = 8{,}7\cdot
>   % 10^{-7}~\mathrm{fm}\nonumber
> \end{displaymath}
>
> The issue is with the \label command. It compiles correctly when I
> remove it. I think the issue is that displaymath is internally
> equation*, which is unnumbered and it cannot produce a number in \ref
> anyway.
> There must be something else going on though, because when I try a
> following MWE:
>
> \documentclass{article}
> \usepackage{amsmath}
> \begin{document}
> \begin{displaymath}
>   a=b
>   \label{ahoj}
> \end{displaymath}
>
> Ref: \ref{ahoj}
> \end{document}
>
> it compiles without errors. It even produces hyperlinks, just the
> hyperlink produced by \ref is empty, so you cannot click on it.
> So there is something going on, but it would be best to remove the
> \label from this displaymath, as it is not useful anyway. You even
> don't reference it anywhere.
>
>
>> I should also note that - even when getting the error messages - the
>> resulting HTML page looks reasonably, but when adding more chapters,
>> the code crashes. So apparently one should avoid these error messages
>> for large documents....
>
> I could compile the sample file using:
>
> make4ht -f html5+dvisvgm_hashes -m draft -c split.cfg -a debug
> exerquiz_exx.tex "svg,2,fn-in"
>
> The -f html5+dvisvgm_hashes option can significantly speed up the
> compilation, because it reuses math images.
> I've also introduced svg and fn-in options, the first one requires
> SVG images, the second puts footnotes at the end of the chapter where
> they were used, instead of standalone files.
>> Maybe the problem can be fixed by an improvement in the configuration
>> file split.cfg??
>>
>
> Other than that, I can see only one issue regarding validity of the
> produced HTML files, there is spurious </form> element in the lasth
> HTML file. I need to investigate where it comes from.
> Best regards,
> Michal