tables
I need a table with 4 rows, 3 columns and a partial horizontal line in column 2-3. I tried:
\documentclass{article}
\begin{document}
\begin{table}
{
\begin{center}
\begin{tabular}{|c|c|c|}
\hline
Col 1 & \multicolumn{2}{|c|}{Col 2-3 Heading}\\
\cline{2-3} & Col 2 & Col 3\\
\hline
- & - & -\\
\hline
- & - & - \\
\hline
- & - & - \\
\hline
\end{tabular}
\end{center}
}
\end{table}
\end{document}
which yielded:
Note that, width of column 2 & 3 are not equal. How can I fix that?
The problem is that the \begin{...} and \end{...} pair commands automatically create a "group" so that, in effect, the & and \\ are "out of scope" for the tabular, while inside the "production" environment they just show up at a place where the compiler is not expecting them.
A second problem with your definitions is that, even if they would work, they would be adding an extra \\ at the end of the tabular, adding an unwanted space at the end. Perhaps some more appropriate definitions would be
\documentclass[a4paper,10pt]{article}
\newcommand{\production}[1]{#1 ::= &}
\newenvironment{grammar}{\tabular{p{3cm}l}}{\endtabular}
\begin{document}
\begin{grammar}
\production{XmlStartTag} ... \\
\production{XmlOtherTag} ... \\
\production{XmlEndTag} ...
\end{grammar}
\end{document}
Note no \\ at the end of the last production. Also in the definition of the grammar you don't need to repeat the work of \begin/\end, and you can instead directly use \tabular and \endtabular.
Here's an example using your idea of putting the headers horizontally and connecting them to the columns with arrows:
\documentclass{beamer}
\usepackage{tikz}
\usepackage{tabularx}
\newcommand*{\hnode}[1]{\tikz[remember picture] \node (#1) {};}
% I am actually using a similar theme
% The space ``wasted'' is similar for PaloAlto though
\usetheme{PaloAlto}
\begin{document}
\frame
{
\frametitle{Comparision of boost implemented graph classes}
\begin{tabular}{l}
%
% Column Headers, first column is empts
%
compressed\_sparse\_row\_graph\hnode{H3}\\
adjacency\_matrix\hnode{H2}\\
adjacency\_list\hnode{H1}\\
\\
\end{tabular}
\begin{tabularx}{\textwidth}{X c c c}
%
& \hnode{C1}
& \hnode{C2}
& \hnode{C3}\\
% Rows, I suspect I need about 10
% Class adjlist adjmatrix csrg
\hline
AdjacencyGraph & Yes & No & Yes \\
Interface \#2 & Yes & No & Yes \\
Interface \#3 & Yes & No & Yes \\
Interface \#4 & Yes & No & Yes \\
Interface \#5 & Yes & No & Yes \\
Interface \#6 & Yes & No & Yes \\
Interface \#7 & Yes & No & Yes \\
Interface \#8 & Yes & No & Yes \\
Interface \#9 & Yes & No & Yes \\
% Rest omitted
\end{tabularx}
\tikz[remember picture,overlay] \draw (H1) [very thick, red,->] -| (C1);
\tikz[remember picture,overlay] \draw (H2) [very thick, red,->] -| (C2);
\tikz[remember picture,overlay] \draw (H3) [very thick, red,->] -| (C3);
}
\end{document}
It actually looks pretty good, if I may say so myself.
Best Answer
If the width of the contents of a spanned cell produced using
\multicolumnis larger then the width of the contents of the individual cells, the extra space is added to the last spanned column, as you have experienced and this example shows even clearer:Two options: you can change to centered
p{...}columns (the two options show this same approach with and without thetabularxpackage):Not related to the question: inside a float is better to use
\centeringand not thecenterenvironment; the later adds extra vertical space which most of the times is undesired.