I have many tables set with {tabularx} but for some of the it seems easier to use {tabu} which works. But if I use both packages and gave the last X column in {longtabu} an S and optional argument it crashes.
So I can “unload” tabularx to make it work which is no option or use another tabular preamble but this isn’t so nice …
\documentclass{article}
\usepackage{tabu,longtable}
\usepackage{tabularx}% comment this out to make it work
\usepackage{siunitx}
\sisetup{locale=DE}
\begin{document}
%\begin{longtabu} to \textwidth{llX[-0.5,l]{S}X[-0.5,l]{S}X[-0.5,l]{S}}
% works with this preamble even when tabularx is loaded:
\begin{longtabu} to \textwidth{llX[-0.5,l]{S}X[-0.5,l]{S}X{S}}
2& 1400& 2,5 & 1,0 &2,3\\
\end{longtabu}
\end{document}
I found How to use siunitx and tabularx together? but it doesn’t help.
\arraybackslashbefore there was a\tabularnewlineso it's not really a re-definition, but yes your solution would work, no need to make it local it would work with TX as well. – David Carlisle Feb 06 '12 at 16:00\arraybackslash. But I now checked: The changes.txt of latex says that \tabularnewline was introduced 1994 (at your request). Why did tabularx never used it for\arraybackslash? And why did array use it when it included\arraybackslashin 2003 ("copied from tabularx")? – Ulrike Fischer Feb 06 '12 at 16:32\arraybackslashissue: http://www.latex-project.org/svnroot/latex2e-public/required/tools/tabularx.dtx – David Carlisle Feb 07 '12 at 00:29