我的文档使用一个命令，该命令每章更新一次。对于某些章节，我需要将其扩展存储为另一个变量（命令）。我需要实际的扩展值，而不是命令。
为了说明这一点，我们使用了 MWE。
\documentclass{book}
\usepackage{etoolbox,ifthen,xspace}
\newcommand{\subjectshort}{Compsci} % this command is used several times in the document
\newcommand{\subjectshortl}{\MakeLowercase{\subjectshort}} % this command is an workaround just for the next command
\newcommand{\abracadabra}[1]{abracadabra:#1}
\newcommand{\chaplabel}[1]{
\ifthenelse{\isundefined{\thischaplabeltmp}}{
\newcommand{\thischaplabeltmp}{\abracadabra{#1}}
} {
\renewcommand{\thischaplabeltmp}{\abracadabra{#1}}
}
\ifthenelse{\isundefined{\thischaplabel}}{
\newcommand{\thischaplabel}{\subjectshortl:mod:\thischaplabeltmp\xspace}
} {
\renewcommand{\thischaplabel}{\subjectshortl:mod:\thischaplabeltmp\xspace}
}
\thischaplabel
}
\begin{document}
\chapter{First chapter}
some content of first chapter\\
\chaplabel{Text specific to first chapter}\\
some more contents of first chapter\\
current thischaplabel = \thischaplabel\\
\expandafter\def\csname tmpstore\endcsname{\thischaplabel\xspace}
current tmpstore = \tmpstore\\ % this is the value I want to be avaibale till I redefine \tmpstore
\chapter{Second chapter}
some content of second chapter\\
\chaplabel{Text specific to second chapter}\\
some more contents of second chapter\\
current thischaplabel = \thischaplabel\\
current tmpstore = \tmpstore\\ % i wanted the earlier expanded value avaibale here too
% writing to an auxiliary file does not produce the expected outcome as shown by the next line
%\expandafter\label{\tmpstore} % this breaks compliing
\chapter{Third chapter}
some content of third chapter\\
\chaplabel{Text specific to third chapter}\\
some more contents of third chapter\\
\chapter{Fourth chapter}
some content of fourth chapter\\
\chaplabel{Text specific to fourth chapter}\\
some more contents of fourth chapter\\
\end{document}
当我第一次在章节中调用时\chaplabel{Text specific to the chapter}，它会创建或更新命令\thischaplabel，然后输出扩展。到目前为止一切顺利。但是在某些章节中，我需要存储当前的扩展值\thischaplabel以便更长时间可用，也许在接下来的 4 个章节中。我尝试在相关章节中调用以下内容
\expandafter\def\csname tmpstore\endcsname{\thischaplabel\xspace}
但是它似乎从不存储扩展值。相反， \tmpstore 获取最新的值\thischaplabel。实际上它只是 的一个别名\thischaplabel。
我如何使用\tmpstore像保存常量字符串（其本身是另一个命令的扩展形式）的临时变量？
原因：我还需要将 /tmpstore 值写入辅助文件（稍后处理）。我在此辅助文件中看到的输出是立即展开的命令，而不是最终展开的（字符串）值。这可以通过在\expandafter\label{\tmpstore}任何地方发出指令来看到。除此之外，它也无法正确编译。
答案1
使用\protected@edef而不是\def。
需要受保护的\edef是因为保存的数量\tmpstore，即\thischapterlabel包含形式为\MakeLowercase和的不可扩展宏\xspace。
\documentclass{book}
\usepackage{etoolbox,ifthen,xspace}
\newcommand{\subjectshort}{Compsci} % this command is used several times in the document
\newcommand{\subjectshortl}{\MakeLowercase{\subjectshort}} % this command is an workaround just for the next command
\newcommand{\abracadabra}[1]{abracadabra:#1}
\newcommand{\chaplabel}[1]{
\ifthenelse{\isundefined{\thischaplabeltmp}}{
\newcommand{\thischaplabeltmp}{\abracadabra{#1}}
} {
\renewcommand{\thischaplabeltmp}{\abracadabra{#1}}
}
\ifthenelse{\isundefined{\thischaplabel}}{
\newcommand{\thischaplabel}{\subjectshortl:mod:\thischaplabeltmp\xspace}
} {
\renewcommand{\thischaplabel}{\subjectshortl:mod:\thischaplabeltmp\xspace}
}
\thischaplabel
}
\begin{document}
\chapter{First chapter}
some content of first chapter\\
\chaplabel{Text specific to first chapter}\\
some more contents of first chapter\\
current thischaplabel = \thischaplabel\\
\makeatletter%
\expandafter\protected@edef\csname tmpstore\endcsname{\thischaplabel\xspace}
\makeatother%
current tmpstore = \tmpstore\\ % this is the value I want to be avaibale till I redefine \tmpstore
\chapter{Second chapter}
some content of second chapter\\
\chaplabel{Text specific to second chapter}\\
some more contents of second chapter\\
current thischaplabel = \thischaplabel\\
current tmpstore = \tmpstore\\ % i wanted the earlier expanded value available here too
\chapter{Third chapter}
some content of third chapter\\
\chaplabel{Text specific to third chapter}\\
some more contents of third chapter\\
\chapter{Fourth chapter}
some content of fourth chapter\\
\chaplabel{Text specific to fourth chapter}\\
some more contents of fourth chapter\\
\end{document}
楼主编辑了这个问题，并指出他/她想用它\tmpstore作为标签。正如我所解释的，标签中不能使用不可膨胀的材料。不过，我在这里做了两件事。我\xspace用
\def\xspace{}% GETS RID OF ONE UNEXPANDABILITY (DISABLES \xspace}
（显然，正确的方法是不使用它，而不是禁用它；我在这里这样做只是为了演示），然后我想出一个更可扩展的形式，\MakeLowercase形式为
\usepackage{expl3}
\ExplSyntaxOn
\cs_set_eq:NN \explower \tl_lower_case:n% GETS RID OF SECOND UNEXPANDABILITY
\ExplSyntaxOff
我使用
\newcommand{\subjectshortl}{\explower{\subjectshort}} % this command is an workaround just for the next command
通过这些更改，我可以让它与简单的一起工作\edef，然后我可以显示它其中没有未扩展的材料（使用\detokenize）并将其用作参数\label。
底线是\xspace和\MakeLowercase不可扩展，因此不是论点中可接受的组成部分\label。
\documentclass{book}
\usepackage{etoolbox,ifthen,xspace}
\newcommand{\subjectshort}{Compsci} % this command is used several times in the document
\newcommand{\subjectshortl}{\explower{\subjectshort}} % this command is an workaround just for the next command
\newcommand{\abracadabra}[1]{abracadabra:#1}
\newcommand{\chaplabel}[1]{
\ifthenelse{\isundefined{\thischaplabeltmp}}{
\newcommand{\thischaplabeltmp}{\abracadabra{#1}}
} {
\renewcommand{\thischaplabeltmp}{\abracadabra{#1}}
}
\ifthenelse{\isundefined{\thischaplabel}}{
\newcommand{\thischaplabel}{\subjectshortl:mod:\thischaplabeltmp\xspace}
} {
\renewcommand{\thischaplabel}{\subjectshortl:mod:\thischaplabeltmp\xspace}
}
\thischaplabel
}
\def\xspace{}% GETS RID OF ONE UNEXPANDABILITY (DISABLES \xspace}
\usepackage{expl3}
\ExplSyntaxOn
\cs_set_eq:NN \explower \tl_lower_case:n% GETS RID OF SECOND UNEXPANDABILITY
\ExplSyntaxOff
\begin{document}
\chapter{First chapter}
some content of first chapter\\
\chaplabel{Text specific to first chapter}\\
some more contents of first chapter\\
current thischaplabel = \thischaplabel\\
\makeatletter%
\expandafter\edef\csname tmpstore\endcsname{\thischaplabel\xspace}
\makeatother%
current tmpstore = \tmpstore\\ % this is the value I want to be avaibale till I redefine \tmpstore
\chapter{Second chapter}
some content of second chapter\\
\chaplabel{Text specific to second chapter}\\
some more contents of second chapter\\
current thischaplabel = \thischaplabel\\
current tmpstore = \tmpstore\\ % i wanted the earlier expanded value avaibale here too
Tokens of \textbackslash tmpstore:\\
\detokenize\expandafter{\tmpstore} % this breaks compliing
Using it as a label:
\expandafter\label\expandafter{\tmpstore} % this breaks compliing
\chapter{Third chapter}
some content of third chapter\\
\chaplabel{Text specific to third chapter}\\
some more contents of third chapter\\
\chapter{Fourth chapter}
some content of fourth chapter\\
\chaplabel{Text specific to fourth chapter}\\
some more contents of fourth chapter\\
\end{document}
