如何标记物品

Question

是否可以按以下方式用乳胶标记物品：

我们有以下定理：

定理 3.2

（我）等等等等

（二）ble ble ble

（三）嘟嘟嘟嘟

因此我想将该项目命名为（II）：

通过定理 3.2（II），我们很容易看出……

我可以在 latex 文件中写入任何命令，让“3.2 (II)”自动显示在 PDF 中吗？标准命令“\label、\ref”不能满足我的要求。

谢谢

Answer 1

希望这就是你要找的。借助enumitem包，我们可以定义对项目的引用，以便\thethm (\Roman*)包含定理数。

请注意，您必须更改\thethm为用于定理的计数器。

梅威瑟：

\documentclass{article}
\usepackage{amsthm}
\usepackage{enumitem}

\newtheorem{thm}{Theorem}[section]

\begin{document}
\section{Theorems}

\begin{thm}
  We have the following theorem:
  \begin{enumerate}[label=\upshape(\Roman*),ref=\thethm (\Roman*)]
    \item\label{th:first} bla bla bla
    \item\label{th:second} ble ble ble
    \item\label{th:third} bli bli bli
  \end{enumerate}
\end{thm}

We see easily by the theorem \ref{th:second} that...

\end{document} 

输出

如果您需要在列表后立即添加定理标题，您可以将其添加before=\leavevmode到环境选项中enumerate。

\documentclass{article}
\usepackage{amsthm}
\usepackage{enumitem}

\newtheorem{thm}{Theorem}[section]

\begin{document}
\section{Theorems}
We have the following theorem:

\begin{thm}
  \begin{enumerate}[before=\leavevmode,label=\upshape(\Roman*),ref=\thethm (\Roman*)]
    \item\label{th:first} bla bla bla
    \item\label{th:second} ble ble ble
    \item\label{th:third} bli bli bli
  \end{enumerate}
\end{thm}

We see easily by the theorem \ref{th:second} that...

\end{document} 

输出：

Answer 2

假设您使用的是“基本”文档类（例如article），您可以按如下方式进行：

• 加载ntheorem包并选择在标题后插入换行符的定理样式，

• 使用该chngcntr包确保定理的编号在每个新部分重新开始，并且

• 重新设置低级 LaTeX 参数\theenumi、\labelenumi和 ，\p@enumi以适当获得直立形状的大写罗马数字，并在交叉引用中使用定理编号作为前缀。

\documentclass{article}

%% A. Theorem style with line break after header
\usepackage{ntheorem}
\theoremstyle{break}
\newtheorem{theorem}{Theorem}
%% B. Number theorems by section 
\usepackage{chngcntr}
\counterwithin{theorem}{section}
%% C. Labelling of level-1 enumerated items
\renewcommand\theenumi{\textup{(\Roman{enumi})}}
\renewcommand\labelenumi{\theenumi}
\makeatletter
\renewcommand\p@enumi{\thetheorem\,}
\makeatother

\begin{document}

\setcounter{section}{3} % just for this example
\setcounter{theorem}{1}

\begin{theorem}
\begin{enumerate}
   \item bla bla bla
   \item \label{item:2} ble ble ble
   \item bli bli bli
\end{enumerate}
\end{theorem}

As we can easily see by Theorem \ref{item:2}, \dots
\end{document}