带有 ntheorem 的定理符号

Question

为什么我现在用这个代码得到一个定理符号

\documentclass{article}

\usepackage{mathtools}
\usepackage{ntheorem}
\usepackage{mdframed}

\mdfsetup{%
    skipabove=\topskip,
    skipbelow=\topskip,
    linecolor=blue,
    ntheorem=true
}

\theoremstyle{break}
\theorembodyfont{\normalfont}
\theoremsymbol{\ensuremath{\diamondsuit}}
\newmdtheoremenv{definition}{Definition}[section]

\begin{document}

\begin{definition}[Some Definition]
This is a definition with an equation
\begin{equation*}
2 + 2 = 4,
\end{equation*}
and some text.
\end{definition}

\end{document}

我得到的是

但我想要在定义的右下角有一个小符号，表示定义已完成。

Answer 1

ntheorem使用选项加载包thmmarks。

\documentclass{article}

\usepackage{mathtools}
\usepackage[thmmarks]{ntheorem}
\usepackage{mdframed}

\mdfsetup{%
    skipabove=\topskip,
    skipbelow=\topskip,
    linecolor=blue,
    ntheorem=true
}

\theoremstyle{break}
\theorembodyfont{\normalfont}
\theoremsymbol{\ensuremath{\diamondsuit}}
\newmdtheoremenv{definition}{Definition}[section]

\begin{document}

\begin{definition}[Some Definition]
This is a definition with an equation
\begin{equation*}
2 + 2 = 4,
\end{equation*}
and some text.
\end{definition}

\end{document}