如何*僅*將自訂定理環境應用於嵌套定理？

Question

在上一個線程，我詢問了定義自訂定理環境的可能性，其 QED 符號將是定理名稱/數字/標籤的盒裝版本。在那裡，我得到了以下解決方案：

\documentclass{book}
\usepackage{amsthm,xpatch}

\makeatletter
\let\qed@empty\openbox % <--- change here, if desired
\def\@begintheorem#1#2[#3]{%
  \deferred@thm@head{%
    \the\thm@headfont\thm@indent
    \@ifempty{#1}
      {\let\thmname\@gobble}
      {\let\thmname\@iden}%
    \@ifempty{#2}
      {\let\thmnumber\@gobble\global\let\qed@current\qed@empty}
      {\let\thmnumber\@iden\xdef\qed@current{#2}}%
    \@ifempty{#3}
      {\let\thmnote\@gobble}
      {\let\thmnote\@iden}%
    \thm@swap\swappedhead
    \thmhead{#1}{#2}{#3}%
    \the\thm@headpunct\thmheadnl\hskip\thm@headsep
  }\ignorespaces
}
\renewcommand{\qedsymbol}{%
  \ifx\qed@thiscurrent\qed@empty
    \qed@empty
  \else
    \fbox{\scriptsize\qed@thiscurrent}%
  \fi
}
\renewcommand{\proofname}{%
  Proof%
  \ifx\qed@thiscurrent\qed@empty
  \else
    \ of \qed@thiscurrent
  \fi
}
\xpretocmd{\proof}{\let\qed@thiscurrent\qed@current}{}{}
\newenvironment{proof*}[1]
  {\def\qed@thiscurrent{\ref{#1}}\proof}
  {\endproof}
\makeatother

\newtheorem{thm}{Theorem}[section]
\newtheorem{lem}[thm]{Lemma}
\newtheorem*{nthm}{Theorem}

\begin{document}

\chapter{Title}

\section{Title}

\begin{thm}
Pigs can fly.
\end{thm}

\begin{proof}
Would you doubt it?
\end{proof}

\begin{nthm}
Unnumbered.
\end{nthm}
\begin{proof}
What should we say?
\end{proof}

The following theorem will be proved later.

\begin{thm}\label{thm:later}
$P=NP$.
\end{thm}

Long text here.

\begin{proof*}{thm:later}
Oh, well! Should I really do it? We'll use the following lemma.

\begin{lem}
Something surely can fly.
\end{lem}
\begin{proof}
Clear.
\end{proof}
Now use the lemma and apply the well known identity
\[
1=0.\qedhere
\]
\end{proof*}
\end{document}

該程式碼的結果如下：

是否可以以“檢測嵌套”的方式修改給定的代碼，即“頂級”（未嵌套）上的定理/引理/命題保持其通常的 QED 符號，而定理/引理/命題在後續級別（嵌套在頂層層級中的層級）上以QED 符號指定，這些符號是定理/引理/命題的盒裝名稱/數字/標籤？

除了上面的程式碼之外，我沒有 MWE，因為我根本不知道如何寫這樣的東西。我在 TeX.SX 上找到了幾個其他論壇（這裡和這裡），它處理格式化嵌套環境，但我始終無法使我擁有的程式碼適應其中提供的程式碼。

任何幫助將不勝感激。

Answer 1

這個想法是在證明開始時添加一個為 true 的條件，並相應地更改程式碼：如果條件為 false，則我們不會嵌套，因此我們設定\qed@current為\qed@empty，否則我們使用與其他答案相同的機制。

\documentclass{book}
\usepackage{amsthm,xpatch}

\makeatletter
\let\qed@empty\openbox % <--- change here, if desired
\def\@begintheorem#1#2[#3]{%
  \deferred@thm@head{%
    \the\thm@headfont\thm@indent
    \@ifempty{#1}
      {\let\thmname\@gobble}
      {\let\thmname\@iden}%
    \@ifempty{#2}
      {\let\thmnumber\@gobble\global\let\qed@current\qed@empty}
      {\let\thmnumber\@iden
       \ifqed@inproof
         \xdef\qed@current{#2}%
       \else
         \global\let\qed@current\qed@empty
       \fi}%
    \@ifempty{#3}
      {\let\thmnote\@gobble}
      {\let\thmnote\@iden}%
    \thm@swap\swappedhead
    \thmhead{#1}{#2}{#3}%
    \the\thm@headpunct\thmheadnl\hskip\thm@headsep
  }\ignorespaces
}
\renewcommand{\qedsymbol}{%
  \ifx\qed@thiscurrent\qed@empty
    \qed@empty
  \else
    \fbox{\scriptsize\protect\qed@thiscurrent}%
  \fi
}
\renewcommand{\proofname}{%
  Proof%
  \ifx\qed@thiscurrent\qed@empty
  \else
    \ of \qed@thiscurrent
  \fi
}
\newif\ifqed@inproof
\xpretocmd{\proof}{\let\qed@thiscurrent\qed@current\qed@inprooftrue}{}{}
\newenvironment{proof*}[1]
  {\def\qed@thiscurrent{\ref{#1}}\proof}
  {\endproof}
\def\debug{\show\qed@thiscurrent}
\makeatother

\newtheorem{thm}{Theorem}[section]
\newtheorem{lem}[thm]{Lemma}
\newtheorem*{nthm}{Theorem}

\begin{document}

\chapter{Title}

\section{Title}

\begin{thm}
Pigs can fly.
\end{thm}

\begin{proof}
Would you doubt it?
\end{proof}

\begin{nthm}
Unnumbered.
\end{nthm}
\begin{proof}
What should we say?
\end{proof}

The following theorem will be proved later.

\begin{thm}\label{thm:later}
$P=NP$.
\end{thm}

Long text here.

\begin{proof*}{thm:later}
Oh, well! Should I really do it? We'll use the following lemma.

\begin{lem}
Something surely can fly.
\end{lem}
\begin{proof}
Clear.
\end{proof}
Now use the lemma and apply the well known identity
\[
1=0.\qedhere
\]
\end{proof*}

\end{document}