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.
Since the whole outer cell, which contains \specialcell should be bold, \bfseries can be specified in the outer cell, right before \specialcell:
... & \bfseries\specialcell{...} & ...
This can also be put into a macro \specialcellbold, see the following example:
\documentclass{report}
\usepackage{booktabs}
\usepackage{array}
\newcommand*\rotbf[1]{\rotatebox{90}{\textbf{#1}}}
\newcommand{\specialcell}[2][c]{\begin{tabular}[#1]{@{}l@{}}#2\end{tabular}}
\newcommand{\specialcellbold}[2][c]{%
\bfseries
\begin{tabular}[#1]{@{}l@{}}#2\end{tabular}%
}
\begin{document}
\begin{table}[hbr]
\centering
\label{tbl:heatwheel_res}
\begin{tabular}{llll}
\toprule
\textbf{Parameter} &
\specialcellbold{Exhaust\\air} &
\specialcellbold{Exhaust and\\ outdoor air} &
\specialcellbold{Heat wheel\\(80~\%)} \\
\midrule
Heat recovery [\%] & 89,6 \% & 89,6 \% & 77,4 \% \\
Real heat recovery [\%] & 50,5 \% & 52,1 \% & - \\
Net energy need for VH and SH & 27,7 & 27,0 & 15,8 \\
\specialcell{Delivered energy for\\DHW, VH and SH} & 31,1 & 27,6 & 45,6 \\
\bottomrule
\end{tabular}
\end{table}
\end{document}
The table formatted a little different:
\documentclass{report}
\usepackage{booktabs}
% \usepackage{array}% It can also be loaded explicitly, implicitly it is
% loaded by siunitx
\usepackage{siunitx}
% \sisetup{output-decimal-marker={,}}% OP now wants to have the default dot
\sisetup{detect-weight, mode=text}
\newcommand*\rotbf[1]{\rotatebox{90}{\textbf{#1}}}
\newcommand{\specialcell}[2][b]{\begin{tabular}[#1]{@{}c@{}}#2\end{tabular}}
\newcommand{\specialcellbold}[2][b]{%
\bfseries
\sisetup{text-rm=\bfseries}%
\begin{tabular}[#1]{@{}c@{}}#2\end{tabular}%
}
\newcommand*{\leftspecialcell}[2][b]{%
\begin{tabular}[#1]{@{}l@{}}#2\end{tabular}%
}
\begin{document}
\begin{table}[hbr]
\centering
\label{tbl:heatwheel_res}
\begin{tabular}{l*{3}{S[table-format=2.1]}}
\toprule
\textbf{Parameter} &
{\specialcellbold{Exhaust\\air}} &
{\specialcellbold{Exhaust and\\ outdoor air}} &
{\specialcellbold{Heat wheel\\(\SI{80}{\percent})}} \\
\midrule
Heat recovery [\si{\percent}] & 89,6 & 89,6 & 77,4 \\
Real heat recovery [\si{\percent}] & 50,5 & 52,1 & {---} \\
Net energy need for VH and SH & 27,7 & 27,0 & 15,8 \\
\leftspecialcell{Delivered energy for\\
\quad DHW, VH and SH} & 31,1 & 27,6 & 45,6 \\
\bottomrule
\end{tabular}
\end{table}
\end{document}
Remarks:
- Bottom aligned header row.
- Columns 2 to 4 are centered.
- Use of package
siunitx for aligning at the decimal marker and for setting the percent signs.
- The lines after the first line in a left cell is indented.
and the alignment follows the bottom line instead of vertical
centering.
- Use of em dash instead of the hyphen for the missing entry.
- Redundant percent signs removed.
- Changed the output decimal marker to the default dot (see comment of ROLF).
- A little crude is
\siunit{text-rm=\bfseries}. Option detect-weight did not work inside an S-column.
Update
I, Svend Tveskæg, found the code not very easy to read to I cleaned it up a bit (I hope it's okay):
\documentclass{report}
\usepackage{booktabs}
\usepackage{siunitx}
\sisetup{
% output-decimal-marker = {,},
detect-weight,
mode = text
}
\newcommand*{\specialcell}[2][b]{%
\begin{tabular}[#1]{@{}c@{}}#2\end{tabular}%
}
\newcommand*{\specialcellbold}[2][b]{%
\bfseries
\sisetup{text-rm = \bfseries}%
\begin{tabular}[#1]{@{}c@{}}#2\end{tabular}%
}
\newcommand*{\leftspecialcell}[2][b]{%
\begin{tabular}[#1]{@{}l@{}}#2\end{tabular}%
}
\begin{document}
\begin{table}[htbp]
\centering
\label{tbl:heatwheel-res}
\begin{tabular}{l *{3}{S[table-format = 2.1]}}
\toprule
\textbf{Parameter} &
{\specialcellbold{Exhaust \\ air}} &
{\specialcellbold{Exhaust and\\ outdoor air}} &
{\specialcellbold{Heat wheel \\ (\SI{80}{\percent})}} \\
\midrule
Heat recovery [\si{\percent}] & 89,6 & 89,6 & 77,4 \\
Real heat recovery [\si{\percent}] & 50,5 & 52,1 & {---} \\
Net energy need for VH and SH & 27,7 & 27,0 & 15,8 \\
\leftspecialcell{Delivered energy for \\
\quad DHW, VH and SH} & 31,1 & 27,6 & 45,6 \\
\bottomrule
\end{tabular}
\end{table}
\end{document}
Best Answer
You are probably looking for the following layout:
Note that the table caption is not properly aligned since the
tabularstructure is too wide. If need be, you can adjust the column separation which provides a tighter view and possibly make the table fit within the page boundary.The default of
\tabcolsepis6pt. Anything smaller will shrink thetabularhorizontally. Using something like\setlength{\tabcolsep}{3pt}. You could also consider increasing the text block margin usinggeometry.