如何在定理标题中换行？

Question

我有一个定理标题，其长度超过页面宽度。如何将标题分成两行？

\begin{theorem}[this title is to long for one line]
the theorem
\end{theorem}

Answer 1

您能否提供有关所使用的文档类和包的更多信息？例如，以下代码似乎可以处理长标题和描述，但可能无法解决您的问题：

\documentclass{amsart}
\newtheorem{theorem}{Theorem}
\begin{document}
\begin{theorem}[this theorem has a long title that extends well over a line but is handled without any manual intervention on the author's partand even this description goes over a line]
body of the theorem
\end{theorem}
\end{document}

如果你能提供类似的最小工作示例这表明了你的问题，这将帮助其他人比我在这里更有用地发表评论。

根据您的评论（并假设您的意思是scrbook对于课程，那么使用amsthm包可能就足够了，例如：

\documentclass[11pt,a4paper,twoside ,fleqn,headsepline]{scrbook}
\usepackage{amsthm}
\newtheorem{theorem}{Theorem}
\begin{document}
\begin{theorem}[this theorem has a long title that extends well over a line but is handled without any manual intervention on the author's part and even this description goes over a line]
Body of the theorem
\end{theorem}
\end{document}

Answer 2

LaTeX默认定理环境的解决方案：

\makeatletter
\renewcommand*{\@opargbegintheorem}[3]{\trivlist
  \item[\hskip \labelsep{\bfseries #1\ #2}] \textbf{(#3)}\ \itshape}
\makeatother

这里重新定义了宏\@opargbegintheorem，它原本包含

  \item[\hskip \labelsep{\bfseries #1\ #2\ (#3)}]\itshape}

因此，可选的定理标题已被移至标签之后，而不是在标签内，所以现在可以换行。

测试示例：

\documentclass{book}
\newtheorem{theorem}{Theorem}
\makeatletter
\renewcommand*{\@opargbegintheorem}[3]{\trivlist
      \item[\hskip \labelsep{\bfseries #1\ #2}] \textbf{(#3)}\ \itshape}
\makeatother
\begin{document}
\begin{theorem}[This theorem has a very long title which requires a line break]
text
\end{theorem}
\end{document}

信息就这么多。我建议使用功能强大的定理包，例如amssthm或，ntheorem它可以扩展 LaTeX 的定理功能。

Answer 3

就像一些评论关于提供修复ntheorem，我尝试提供一个。它似乎有效——至少在快速测试中——但我不确定它是否 100% 正确（例如，它可能会破坏某些软件包的一些内部约定）。

% https://tex.stackexchange.com/a/179917:
\newcommand*{\NLS}{%
    \par
    \nobreak
    \vspace{-\parskip}%
    \noindent
    \ignorespaces
}

\makeatletter
% From ‘ntheorem.sty’:
\newtheoremstyle{mybreak}%
{\item[\rlap{\vbox{\hbox{\hskip\labelsep \theorem@headerfont
                ##1\ ##2\theorem@separator}\hbox{\strut}}}]}%
{\item[\hskip\labelsep \theorem@headerfont%
    ##1\ ##2]\hspace*{-\labelsep}{\theorem@headerfont\ (##3)\theorem@separator}\NLS}
\makeatother

梅威瑟：

\documentclass{book}
\usepackage[standard]{ntheorem}

% https://tex.stackexchange.com/a/179917:
\newcommand*{\NLS}{%
    \par
    \nobreak
    \vspace{-\parskip}%
    \noindent
    \ignorespaces
}

\makeatletter
% From ‘ntheorem.sty’:
\newtheoremstyle{mybreak}%\newtheoremstyle{break}%
{\item[\rlap{\vbox{\hbox{\hskip\labelsep \theorem@headerfont
                ##1\ ##2\theorem@separator}\hbox{\strut}}}]}%
{\item[\hskip\labelsep \theorem@headerfont%{\item[\rlap{\vbox{\hbox{\hskip\labelsep \theorem@headerfont
    ##1\ ##2]\hspace*{-\labelsep}{\theorem@headerfont\ (##3)\theorem@separator}\NLS}%##1\ ##2]\hspace*{-\labelsep}{\theorem@headerfont\ (##3)\theorem@separator}\hfill\penalty\@endparpenalty%##1\ ##2\ (##3)\theorem@separator}\hbox{\strut}}}]}
\makeatother

\theoremstyle{mybreak}
\renewtheorem{Theorem}{Theorem}

\usepackage[all]{nowidow}

% For testing:
\usepackage[english]{babel}
\usepackage{blindtext}
\blindmathtrue

\begin{document}
    \begin{Theorem}[This theorem has a very long title which requires a line break]
        \blindtext\par
        \blindtext
    \end{Theorem}
    \blindtext\par
    \blindtext
\end{document}