# [lltx] \scantokens differs between LaTeX and plain?

Arno Trautmann Arno.Trautmann at gmx.de
Tue Nov 15 10:18:40 CET 2011

Hi all!

After I had trouble with the tabu package, Philipp Stephani posted the
following minimal example on texhax that causes the problem. The code
works with XeLaTeX and pdfLaTeX, and with every plain flavour (without
\documentclass etc. of course):

\documentclass{minimal}
\begin{document}
\begingroup
\obeylines%
\endlinechar=10 %
\global\toks0{
}%
\endgroup%
$\scantokens\expandafter{\expandafter$\the\toks0$}$
\end{document}

But with LuaLaTeX, this throws the following error:

./test.tex:11: Missing $inserted. <inserted text>$
l.11 \end{document}

?

Does anyone have an idea what's going on? In what point does LuaLaTeX
differ from the other formats? And is it a bug or a feature? I guessed
it could be related to fonts as that is the only thing that seems to be
different in the formats; however, Will Robertson stated on texhax:

“There's font change in \everymath in LaTeX (actually it's
\frozen at everymath); but even if you empty it (\frozen at everymath={}), the
error still occurs. I think the discussion should be moved to the LuaTeX
and LuaLaTeX lists.”

So, any other ideas?

cheers
Arno