突出显示文本中第一次出现的引用

Question

我正在为我们的研究所制作一个 LaTeX 模板。指南规定引用图形、方程式或表格时应采用一种不寻常的风格。第一次在文中提到它们时，必须加下划线。那么我该怎么做才能让它自动运行呢？我已经尝试了一些词汇表和首字母缩略词，但没有任何效果。

我很高兴收到你的来信，Bernte

Answer 1

以下是修改我的答案回答上一个问题，要求在第一次引用时添加边注。这使用该cleveref包允许上下文感知引用，这使得在名称和数字下划线变得容易。

编辑：正如下面的@egreg所指出的，如果将引用列表传递给，则先前的答案将中断\cref。为了纠正这个问题，现在检查传递的参数是否包含逗号。如果是，则无论引用如何，都不会执行下划线。换句话说，这种方法将在第一次单独进行引用时加下划线。

\documentclass{article}

\usepackage{lipsum}
\usepackage{multicol}

\usepackage[left=1.5in,right=1in]{geometry}

\usepackage{cleveref}
\crefname{equation}{Equation}{Equations}
\crefname{figure}{Figure}{Figures}
\crefname{table}{Table}{Tables}

\usepackage{xstring}    

\makeatletter
%Redefine \cref so that it will make a margin note if the passed label is referenced for the first time.
\let\oldcref=\cref
\def\cref#1{%
    \IfSubStr{#1}{,}{\oldcref{#1}}{%
    %check if the label has already been referenced.
    \ifcsname marginnote@#1\endcsname
        %already exists...therefore not the first citation
        \oldcref{#1}%
    \else
        \underline{\oldcref{#1}}%}
        \expandafter\gdef\csname marginnote@#1\endcsname{}%first citation...with this defined, will not underline again
    \fi
    }}
\makeatother

\author{John Doe}
\title{Automatic underlining of the first use of a reference}

\begin{document}
  \maketitle
  \begin{multicols}{2}

  See \cref{fig:figure}. \lipsum[1] 

  A new reference to \cref{fig:figure} is not underlined.

  Let's do the same with an equation.
  \begin{equation}
    \label{eq:1}f(x) = x^2
  \end{equation}

  Refering to \cref{eq:1} for the first time, there should be a marginal note, as is visible here, but it shoudl begin with  ``Eq.'', not ``Fig.''.
  Here we can test a list of references \cref{eq:1,tab:1,fig:figure} which should bypass the underling no matter the contents.
  Adding another reference to \cref{eq:1} does not result in an underline; however, referring to \cref{tab:1} for the first time does.

  \end{multicols}

% lets put a table and a figure
  \begin{table}
    \caption{Table title}
    \label{tab:1}
    \begin{tabular}{cc}
      x & y \\ \hline 
      3 & 3 \\
      4 & 4 \\ \hline
    \end{tabular}
  \end{table}

  \begin{figure}
    \centering\rule{150pt}{10pt}
    \caption{A figure}\label{fig:figure}
  \end{figure}

\end{document}