Re: very strange LaTeX error

["Joost Kremers" <joostkremers@fastmail.fm>]

On Fri, Dec 20, 2019, at 12:56 PM, Fraga, Eric wrote:
> #+begin_src latex
>   \documentclass{scrartcl}
>   \begin{document}
>   % packages deleted, none of which is used anyway in the following
>   \tableofcontents
> 
>   \section{some results}
>   \label{sec:org4f5891c}
>   \begin{table}[hbtp]
>   \label{atable}
>   \centering
>   \begin{tabular}{lrrr}
>   \hline
>   x & z1 & z2 & g\\
>   \hline
>   [0.0005, 0.05, 0.5] & 90000.0 & 0.05 & 0.0\\
>   [0.000787451, 0.0575948, 0.5] & 110000.0 & 0.05759476698672508 & 0.0\\
>   \hline
>   \end{tabular}
>   \end{table}
>   \end{document}
> #+end_src
> 
> I get errors like this when compiling with pdflatex:
> 
> #+begin_example
>   ! Illegal unit of measure (pt inserted).
>   <to be read again> 
>                      ,
>   l.18 [0.000787451, 0.0575948, 0.5]
>                                      & 110000.0 & 0.05759476698672508 & 0.0\\
>   ! Missing = inserted for \ifdim.
>   <to be read again> 
> #+end_example
> 
> What am I doing wrong? 

You have `[...]` in the first cell of a table row that is not the first row. Few people seem to realise that the double backslash `\\` in LaTeX is a macro that can actually take an optional argument, a measure specifying the height of the newline. So when a table row ends in `\\` (which is the normal case) and the next row starts with an opening bracket, LaTeX assumes it is looking at an optional argument and expects a measure, i.e., a number followed by one of the supported units.

The solution I usually opt for is to enclose the brackets in an additional set of braces: `{[...]}`. Whether Org export can and should automate that, I can't say.

HTH

-- 
  Joost Kremers
  Life has its moments