Error in adding caption longtable

Question

\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?

Answer 1

• \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)

Answer 2

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}
\addparagraphcolumntypes{X}
\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&amp;T_{nM}(x,y)=
    \begin{cases}
        \min(x,y)&amp;\text{if }x+y&gt; 1\\
        0&amp;\text{otherwise}
    \end{cases}&amp;

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

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

    C_{H_2}(x,y)=\dfrac{x+y}{1+xy}

%        \label{tabelnorma}
        \
        \hline
\end{xltabular}

\end{example}
\end{document}