NewDocumentCommand有没有办法扩展在定义点传递的主体？理想情况下，只扩展一次。
这是我的（最小化的）场景。
\documentclass{minimal}
\newcommand*{\baz}{\foo}
\newcommand*{\expandme}{good}
\ExplSyntaxOn
\exp_args:NV \NewDocumentCommand \baz { s D<>{} } {
\expandme% Should get expanded once at definition time.
}
\ExplSyntaxOff
\renewcommand*{\expandme}{bad}
\begin{document}
\foo<bar>% Prints "bad", but I want it to print "good".
\end{document}
进行以下修改会产生Undefined control sequence错误，大概是因为\exp_args参数处理起来很困难{ s D<>{} }。
\exp_args:NVNo \NewDocumentCommand \baz { s D<>{} } {
\expandme% Should get expanded once at definition time.
}
最后，请注意以下解决方案，它在最简单的情况下有效，但当\bar可以采取多个值时会出现问题，并且每个值都会重复此代码（就像我的真实情况一样）。
\exp_args:NNV \cs_set:Npn \tmp \expandme
% alternatively to the above line, I think: \edef\tmp\expandme
\exp_args:NV \NewDocumentCommand \baz { s D<>{} } {
\tmp
}
答案1
您可以\expanded在最近的 tex 版本中使用：
\documentclass{minimal}
\newcommand*{\baz}{\foo}
\newcommand*{\expandme}{good}
\ExplSyntaxOn
\expanded{\noexpand\NewDocumentCommand\expandafter\noexpand\baz { s D<>{} } {
\unexpanded\expandafter{\expandme}% Should get expanded once at definition time.
}}
\ExplSyntaxOff
\renewcommand*{\expandme}{bad}
\begin{document}
\foo<bar>% Prints "bad", but I want it to print "good".
\end{document}
或者您可以将其打包为自定义 VnV 参数列表
\documentclass{minimal}
\newcommand*{\baz}{\foo}
\newcommand*{\expandme}{good}
\ExplSyntaxOn
\exp_args_generate:n{VnV}
\exp_args:NVnV\NewDocumentCommand\baz { s D<>{} } \expandme
\ExplSyntaxOff
\renewcommand*{\expandme}{bad}
\begin{document}
\foo<bar>% Prints "bad", but I want it to print "good".
\end{document}
答案2
如果由于某种原因所需的\exp_args:N...变体不可用，您可以自行处理\use:n：
\documentclass{minimal}
\newcommand*{\baz}{\foo}
\newcommand*{\expandme}{good}
\ExplSyntaxOn
\exp_args:Nno \use:n { \exp_args:NV \NewDocumentCommand \baz { s D<>{} } } {
\expandme% Should get expanded once at definition time.
}
\ExplSyntaxOff
\renewcommand*{\expandme}{bad}
\begin{document}
\foo<bar>% Prints "bad", but I want it to print "good".
\end{document}
答案3
您应该为此定义一个接口。
\documentclass{article}
\newcommand*{\expandme}{good}
\ExplSyntaxOn
\cs_new_protected:Npn \NewDocumentCommandExpandOnce
{
\exp_args:NNno \NewDocumentCommand
}
\ExplSyntaxOff
\NewDocumentCommandExpandOnce \foo { s D<>{} } {%
\expandme% Should get expanded once at definition time.
}
\renewcommand*{\expandme}{bad}
\begin{document}
\foo<bar>% Prints "bad", but I want it to print "good".
\end{document}
您可以检查输出是否“良好”。