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etoolbox ：代码前的钩子

tag-icon • tag-icon etoolbox
etoolbox ：代码前的钩子

有没有办法让钩子在代码之前工作？

\documentclass{article}
\usepackage{etoolbox}

\begin{document}
    
\hhh % this does not work

foo

\appto\hhh{test1}

bar

\hhh % this work

\end{document}

答案1

您可以将值存储在aux文件中并从那里调用它们。

\documentclass{article}
% \setaux{var}{val} sets variable var to val
\newcommand\setaux[2]{\expandafter\xdef\csname aux#1\endcsname{#2}}
% \useaux{var} expands to the value of var
\newcommand\useaux[1]{\ifcsname aux#1\endcsname\csname aux#1\endcsname\else ???\fi}
\makeatletter
% \saveaux{var}{val} sets variable var to val and saves it also to the aux file
% such that the value is available anywhere in the document (after the next run).
\newcommand\saveaux[2]{%
  \immediate\write\@auxout{\string\setaux{#1}{#2}}%
  \setaux{#1}{#2}%
}
\makeatother
\begin{document}
    
\useaux{hhh}

foo

\saveaux{hhh}{test1}

bar

\useaux{hhh}
\end{document}

第一次运行后，你会得到

???
foo
bar
test1

第二次运行后，你会得到

test1
foo
bar
test1

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