With this file:
\documentclass{article}
\usepackage{longtable}
\usepackage{booktabs}
\begin{document}
{
\begin{longtable}{p{.3\textwidth}p{.5\textwidth}}
\midrule
label & value \\
\midrule
(2) label & value \\
\midrule
\end{longtable}
}
\end{document}
running pdflatex, I get:
! Undefined control sequence.
<argument> ...al \expandafter \let \cmrsideswitch
\@tempa \fi \fi
l.10 (2)
label & value \\
There seems to be something about the midrule that makes a left parenthesis invalid. But with tabular instead of longtable, there is no such problem.
Best Answer
You are running into the same problem as in "[" as first character in table row.
booktabs
defines the rules to take an optional argument in the form[..]
or(..)
. The use of(2)
on the row immediately following\midrule
is being interpreted as an optional argument, yet it doesn't match the definition that's expected with that type of optional argument.To avoid this, use