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I defined some macros to store data. Them, I typeset them in a table. If one of the macro is not executed (the corresponding data is not available, the row should not appear.

\documentclass{article}
\usepackage{booktabs}
\usepackage{xifthen}

\DeclareRobustCommand*{\version}[1]{%
\DeclareRobustCommand*{\theversion}{#1}%
}
\DeclareRobustCommand*{\revised}[1]{%
\DeclareRobustCommand*{\therevised}{#1}%
}
\DeclareRobustCommand*{\approved}[1]{%
\DeclareRobustCommand*{\theapproved}{#1}%
}

\newcommand{\mytable}{%
  \begin{tabular*}{\linewidth}{p{0.4\linewidth}p{0.6\linewidth}}
    \toprule
    \ifthenelse{\isundefined{\theversion}}{}{Version: &\theversion\\}%
    \ifthenelse{\isundefined{\therevised}}{}{Revised by: &\therevised\\}%
    \ifthenelse{\isundefined{\theapproved}}{}{Approved by:&\theapproved\\}%
    \bottomrule%
    \end{tabular*}
}


\version{3.2}
\revised{J. Joe}
\approved{A. Uthor}
\begin{document}
\mytable
\end{document}

The code runs fine if I comment the \revised{J. Joe} line. But if I comment \approved{A. Uthor}, them the following error is rised:

(./example.aux)
! Misplaced \noalign.
\bottomrule ->\noalign 
                       {\ifnum 0=`}\fi \@aboverulesep =\aboverulesep \global...
l.34 \mytable

Can anyone help me to find the bug? Thanks in advance.

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1 Answer 1

up vote 3 down vote accepted

I don't know precisely what's going on, but it's clearly an expansion problem. It can be solved with more direct syntax:

\newcommand*{\version}[1]{\newcommand*{\theversion}{#1}}
\newcommand*{\revised}[1]{\newcommand*{\therevised}{#1}}
\newcommand*{\approved}[1]{\newcommand*{\theapproved}{#1}}

\newcommand{\mytable}{%
  \noindent\begin{tabular}{
    p{\dimexpr 0.4\linewidth-2\tabcolsep\relax}
    p{\dimexpr 0.6\linewidth-2\tabcolsep\relax}
    }
    \toprule
    \ifdefined\theversion Version: &\theversion\\\fi
    \ifdefined\therevised Revised by: &\therevised\\\fi
    \ifdefined\theapproved Approved by:&\theapproved\\\fi
    \bottomrule
    \end{tabular}
}

There's no need to declare those commands as robust. Moreover tabular* is useless and it's necessary to correct the width to take into account the separation between columns.

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Thanks for the solution. The actual table is defined inside a sidenote of the tufte-latex package, and it is necessary to use the starred version of tabular (I don't know why) –  zunbeltz Jul 19 '11 at 7:06
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