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xparse：转发空的可选参数

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xparse：转发空的可选参数

我想使用 tcolorbox 来调用定理环境。我的 tcolorbox 应该要求一个可选的标题和一个必需的标签，所以在 xparse 规范中我选择了O{}m。然后，在定义中我使用

before upper={\begin{thm}[#1]\label{#2}},

当标题定义时，效果很好...但不幸的是，当没有定义标题时，这会失败并出现错误

Undefined control sequence.
\ll@thm ...t \thmtformatoptarg {\thmt@shortoptarg 
                                              }\fi 
l.54 \begin{theorem}{thm:mygreatlabel}

我猜是因为thm环境不接受像这样的空可选参数\begin{thm}[] ... \end{thm}。我试图添加条件，但括号被视为真实字符，所以我不知道如何解决这个问题。

谢谢！

梅威瑟：

\documentclass{article}

\usepackage{mathtools}
\usepackage{amssymb, amsthm, amsmath}
\usepackage{thmtools} %%
\usepackage{hyperref}

\newtheorem{thm}{Theorem}[section]
\providecommand*\thmautorefname{Theorem}
\newtheorem{corollary}[thm]{Corollary}
\providecommand*\corollaryautorefname{Corollary}
\newtheorem{lemma}[thm]{Lemma}
\providecommand*\lemmaautorefname{Lemma}

\usepackage{lipsum}
\usepackage[most]{tcolorbox}

% \tcbset{customTheorem/.style={
% }

\NewTColorBox[auto counter, number within=section]{theorem}{O{}m}{ %
    blank,
    breakable,
    before upper={\begin{thm}[#1]\label{#2}},
      after upper={\end{thm}{\itshape See \hyperref[proof:#1]{proof} on page~\pageref{proof@\thetcbcounter}}},
    lowerbox=ignored,
    savelowerto=theorem-\thetcbcounter.tex,
    record={\string\myproof{\thetcbcounter}{theorem-\thetcbcounter.tex}{#2}},
% #1
}


\NewTotalTColorBox{\myproof}{mmm}{ %
  blank,
  breakable,
  before upper={\begin{proof}[Proof of \autoref{#3}]\label{proof:#3}},
    after upper={\end{proof}},
  phantomlabel={proof@#1},
}{\input{#2}}

% \tcbset{no proof/.style={no recording,after upper=\end{thm}}}

\begin{document}
\section{Some theorems}

\tcbstartrecording % [theoremsamazing.records]

\begin{theorem}[My title]{thm:mygreatlabel}
  This theorem works
  \tcblower
  Proof is super obvious
\end{theorem}

\begin{theorem}{thm:mygreatlabel}
  This fails because the environment thm does not accept empty brackets.
  \tcblower
  Proof is not super obvious
\end{theorem}

See, I can refer to \autoref{thm:mygreatlabel}!

\lipsum[2]
\tcbstoprecording

\section{Some amazing theorems}

\tcbinputrecords

\end{document}

答案1

定理颜色箱的定义如下：

\NewTColorBox[auto counter, number within=section]{theorem}{om}{ %
    blank,
    breakable,
    IfNoValueTF={#1}{before upper={\begin{thm}\label{#2}}}{before upper={\begin{thm}[#1]\label{#2}}},
      after upper={\end{thm}{\itshape See \hyperref[proof:#1]{proof} on page~\pageref{proof@\thetcbcounter}}},
    lowerbox=ignored,
    savelowerto=theorem-\thetcbcounter.tex,
    record={\string\myproof{\thetcbcounter}{theorem-\thetcbcounter.tex}{#2}},
% #1
}

这里，不是使用带有空后备的可选参数，而是使用O{}没有后备的可选参数，以区分有参数和无参数的情况。oIfNoValueTF

请注意，\begin{theorem}[]{label}...\end{theorem}明确给出的空可选参数仍然不起作用。

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