在我为环境提供一个可选参数后，环境中部出现意外空白

Question

我试图创造一个这样的环境定理。以下是我迄今为止尝试过的：

\documentclass{article}
\usepackage{xifthen}

\newcounter{numdef}[subsection]
\setcounter{numdef}{0}
\renewcommand\thenumdef{\arabic{numdef}}

\newenvironment{ntdef}[1][]{
    \vspace*{.2em}
    \newcommand\makedef{\stepcounter{numdef}
        \textit{Definition}\ \thesubsection.\thenumdef: 
    }
    \noindent\makedef
}{\par\vspace{.2em}}

\begin{document}
    \section{A}
    \subsection{B}
    \noindent\textit{Definition}\ 1.1.0\ \textit{(Definition 1)}: This is a template\par
    \begin{ntdef}[Definition 1]
        This is the first difinition
    \end{ntdef}

    \begin{ntdef}
        This is the second difinition
    \end{ntdef}
\end{document}

我使用纯文本向模板展示我所认为的前两行所显示的内容。

在我的项目中，环境应该有一个可选参数（为了显示更清晰，我已将显示给定参数的函数移至此测试项目中）。当没有给出选项时，环境工作正常。但是一旦我在选项中给出了名称，水平方向就会出现一个意外的空白，如第二行所示。

是什么原因导致了这个奇怪的问题？

Answer 1

我不确定为什么不使用\newtheorem。无论如何，您需要删除空格和您想要的\addvspace而不是\vspace，以免累积垂直间距。

\documentclass{article}
\usepackage{xifthen}

\newcounter{numdef}[subsection]
\setcounter{numdef}{0}
\renewcommand\thenumdef{\arabic{numdef}}

\newenvironment{ntdef}[1][]{%
  \par\addvspace{.2em}
  \newcommand\makedef{%
    \stepcounter{numdef}%
    \textit{Definition}\ \thesubsection.\thenumdef: \ignorespaces
  }%
  \noindent\makedef
}{\par\addvspace{.2em}}

\begin{document}

\section{A}
\subsection{B}

\noindent\textit{Definition}\ 1.1.0\ \textit{(Definition 1)}: This is a template

\begin{ntdef}[Definition 1]
  This is the first definition
\end{ntdef}

\begin{ntdef}
  This is the second definition
\end{ntdef}

\end{document}

和\newtheorem：

\documentclass{article}
\usepackage{amsthm}

\newtheoremstyle{enkidudefinition}
  {0.2em}       % ABOVESPACE
  {0.2em}       % BELOWSPACE
  {\normalfont} % BODYFONT
  {0pt}         % INDENT (empty value is the same as 0pt)
  {\itshape}    % HEADFONT
  {\normalfont:}% HEADPUNCT
  {5pt plus 1pt minus 1pt} % HEADSPACE
  {}            % CUSTOM-HEAD-SPEC

\theoremstyle{enkidudefinition}
\newtheorem{ntdef}{Definition}[subsection]

\begin{document}

\section{A}
\subsection{B}

\noindent\textit{Definition}\ 1.1.0\ \textit{(Definition 1)}: This is a template

\begin{ntdef}[Definition 1]
  This is the first definition
\end{ntdef}

\begin{ntdef}
  This is the second definition
\end{ntdef}

\end{document}

如果您想要斜体注释：

\documentclass{article}
\usepackage{amsthm}

\newtheoremstyle{enkidudefinition}
  {0.2em}       % ABOVESPACE
  {0.2em}       % BELOWSPACE
  {\normalfont} % BODYFONT
  {0pt}         % INDENT (empty value is the same as 0pt)
  {\itshape}    % HEADFONT
  {\normalfont:}% HEADPUNCT
  {5pt plus 1pt minus 1pt} % HEADSPACE
  {\thmname{#1} \thmnumber{\textup{#2}}\thmnote{ (#3)}} % CUSTOM-HEAD-SPEC

\theoremstyle{enkidudefinition}
\newtheorem{ntdef}{Definition}[subsection]

\begin{document}

\section{A}
\subsection{B}

\noindent\textit{Definition}\ 1.1.0\ \textit{(Definition 1)}: This is a template

\begin{ntdef}[Definition 1]
  This is the first definition
\end{ntdef}

\begin{ntdef}
  This is the second definition
\end{ntdef}

\end{document}