# Error in adding caption longtable

\documentclass[a4paper,oneside,11pt]{article}
\usepackage[left=2.5cm,right=2.5cm,top=4cm,bottom=2.7cm]{geometry}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{graphicx}
\usepackage{array}
\usepackage{newtxtext,newtxmath}
\usepackage{lipsum}
\usepackage{longtable}

\begin{document}
\theoremstyle{definition}
\newtheorem{theorem}{Theorem}[section]
\newtheorem{example}[theorem]{Example}
\lipsum[1-4]
\begin{example}
We present the examples of t-norm and t-conorm using a table as follows.
\begingroup
\renewcommand{\arraystretch}{1.5}
\begin{longtable}{|m{2.3cm}|c|c|}
\caption{Example of t-norm and t-conorm}
\hline
\hfill \textbf{Name}\hfill \strut&\textbf{t-norm}&\textbf{t-conorm}\\
\hline
Standard intersection/ standard union&$T_m(x,y)=\min(x,y)$&$C_m(x,y)=\max(x,y)$\\
\hline
Bounded sum&$T_b(x,y)=\max(0,x+y-1)$&$C_b(x,y)=\min(1,x+y)$\\
\hline
Algebraic product/ Algebraic sum&$T_p(x,y)=xy$&$C_p(x,y)=x+y-xy$\\
\hline
Drastic&$T_D(x,y)= \begin{cases} y&\text{if }x=1\\ x&\text{if }y=1\\ 0&\text{otherwise} \end{cases}$
&
$C_D(x,y)= \begin{cases} y&\text{if }x=0\\ x&\text{if }y=0\\ 1&\text{otherwise} \end{cases}$
\\
\hline
Nilpotent minimum/ Nilpotent maximum&$T_{nM}(x,y)= \begin{cases} \min(x,y)&\text{if }x+y> 1\\ 0&\text{otherwise} \end{cases}$&
$C_{nM}(x,y)= \begin{cases} \max(x,y)&\text{if }x+y<1\\ 1&\text{otherwise} \end{cases}$
\\
\hline
Hamacher product/ Einstein sum&$T_{H_0}(x,y)= \begin{cases} 0&\text{if }x=y=0\\ \dfrac{xy}{x+y-xy}&\text{otherwise} \end{cases}$&
$C_{H_2}(x,y)=\dfrac{x+y}{1+xy}$\label{tabelnorma}
\\
\hline

\end{longtable}
\endgroup
\end{example}
\end{document}


I want to add caption in my table. I'm using longtable. But I don't know why that code gives me an error.

How to fix it?

• after caption{...} had to be table row terminator \. Nov 4, 2020 at 4:08
• Yes. I have added \\ and it fixed. Nov 4, 2020 at 4:57
• See answer below. In it is also some suggestion about your table design. Nov 4, 2020 at 4:58

• \caption inside of longtable had to be terminated with \\ (as is mentioned in my comment}
• sit may be interesting some off-topic table tweaks (see MWE below).
\documentclass[a4paper,oneside,11pt]{article}
\usepackage[hmargin=2.5cm,
vmargin={4cm,2.7cm}]{geometry}
\usepackage{mathtools, amsthm}
\theoremstyle{definition}
\newtheorem{theorem}{Theorem}[section]
\newtheorem{example}[theorem]{Example}
\usepackage{newtxtext,newtxmath}
\usepackage{graphicx}
\usepackage[skip=0.33\lineskip]{caption}
\usepackage{array, longtable}
\usepackage[column=O]{cellspace}
\setlength\cellspacetoplimit{8pt}
\setlength\cellspacebottomlimit{8pt}
\usepackage{lipsum}

\begin{document}
\lipsum[1-4]
\begin{example}
We present the examples of t-norm and t-conorm using a table as follows.
\begingroup
\small
\begin{longtable}{|>{\raggedright}O{m{3.5cm}}|*{2}{>{$}Oc<{$}|}}
\caption{Example of t-norm and t-conorm}
\label{tabelnorma}\\
\hline
\hfil\textbf{Name}
& \textbf{t-norm}   & \textbf{t-conorm}             \\
\hline
Standard intersection/ standard union
& T_m(x,y)=\min(x,y)    & C_m(x,y)=\max(x,y)        \\
\hline
Bounded sum
& T_b(x,y)=\max(0,x+y-1)    & C_b(x,y)=\min(1,x+y)  \\
\hline
Algebraic product/ Algebraic sum
& T_p(x,y)=xy           & C_p(x,y)=x+y-xy           \\
\hline
Drastic
& T_D(x,y) = \begin{cases*}
y & if $x=1$    \\
x & if $y=1$    \\
0 & otherwise
\end{cases*} & C_D(x,y) = \begin{cases*}
y & if $x=0$    \\
x & if $y=0$    \\
1 & otherwise
\end{cases*} \\
\hline
Nilpotent minimum/ Nilpotent maximum
& T_{nM}(x,y) = \begin{cases*}
\min(x,y) & if $x+y>1$   \\
0  & otherwise
\end{cases*} &   C_{nM}(x,y) = \begin{cases*}
\max(x,y) & if $x+y<1$  \\
1 & otherwise
\end{cases*}   \\
\hline
Hamacher product/ Einstein sum
& T_{H_0}(x,y) = \begin{cases*}
0  & if $x=y=0$ \\
\dfrac{xy}{x+y-xy} & otherwise
\end{cases*} &  C_{H_2}(x,y)=\dfrac{x+y}{1+xy}  \\
\hline
\end{longtable}
\endgroup
\end{example}
\lipsum[5]
\end{document}


(red lines show part of page layout)

Since you mentioned in a previous question that you want your table to be as wide as the textwidth, I suggest using xltbular instead of longtable. With its X type column, the table is automatically as wide as a specified width, hence no need to guess the appropriate width of the first column:

\documentclass[a4paper,oneside,11pt]{article}
\usepackage[left=2.5cm,right=2.5cm,top=4cm,bottom=2.7cm]{geometry}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{graphicx}
\usepackage{array}
\usepackage{newtxtext,newtxmath}
\usepackage{lipsum}
\usepackage{xltabular}
\renewcommand{\tabularxcolumn}[1]{m{#1}}
\usepackage[column=0]{cellspace}
\setlength{\cellspacetoplimit}{3\tabcolsep}
\setlength{\cellspacebottomlimit}{\cellspacetoplimit}

\begin{document}
\theoremstyle{definition}
\newtheorem{theorem}{Theorem}[section]
\newtheorem{example}[theorem]{Example}
\lipsum[1-4]
\begin{example}
We present the examples of t-norm and t-conorm using a table as follows.
\begin{xltabular}{\textwidth}{|0{X}|>{$}0c<{$}|>{$}0c<{$}|}
\caption{Example of t-norm and t-conorm}\\
\hline
\hfill \textbf{Name}\hfill \strut&\textbf{t-norm}&\textbf{t-conorm}\\
\hline
Standard intersection/ standard union&T_m(x,y)=\min(x,y)&C_m(x,y)=\max(x,y)\\
\hline
Bounded sum&T_b(x,y)=\max(0,x+y-1)&C_b(x,y)=\min(1,x+y)\\
\hline
Algebraic product/ Algebraic sum&T_p(x,y)=xy&C_p(x,y)=x+y-xy\\
\hline
Drastic&T_D(x,y)=
\begin{cases}
y&\text{if }x=1\\
x&\text{if }y=1\\
0&\text{otherwise}
\end{cases}
&
C_D(x,y)=
\begin{cases}
y&\text{if }x=0\\
x&\text{if }y=0\\
1&\text{otherwise}
\end{cases}

\\
\hline
Nilpotent minimum/ Nilpotent maximum&T_{nM}(x,y)=
\begin{cases}
\min(x,y)&\text{if }x+y> 1\\
0&\text{otherwise}
\end{cases}&

C_{nM}(x,y)=
\begin{cases}
\max(x,y)&\text{if }x+y<1\\
1&\text{otherwise}
\end{cases}

\\
\hline
Hamacher product/ Einstein sum&T_{H_0}(x,y)=
\begin{cases}
0&\text{if }x=y=0\\
\dfrac{xy}{x+y-xy}&\text{otherwise}
\end{cases}&

C_{H_2}(x,y)=\dfrac{x+y}{1+xy}
%        \label{tabelnorma}
\\
\hline

\end{xltabular}
\end{example}
\end{document}