如何在`enumerate`环境中新的`quotation`环境前后产生合适的空格？

Question

首先是一个 MWS，其输出如下。

\documentclass{article}
\usepackage{lipsum,indentfirst}
\setlength{\parindent}{2em}
\setlength{\parskip}{0.3\baselineskip plus 0.2ex minus 0.1ex}

%%%enumerate and so on%%%%%%%%%%%%%%%%%%%%%%%
\usepackage{enumitem}
%space for items--------------------------------------------
\setenumerate[1,2,3]{itemsep=0pt,partopsep=0.3\baselineskip plus 0.2ex minus 0.1ex,parsep=0pt,topsep=0pt}
\setitemize[1,2,3]{itemsep=0pt,partopsep=0.3\baselineskip plus 0.2ex minus 0.1ex,parsep=0pt,topsep=0pt,align=left}
\setdescription{itemsep=0pt,partopsep=0.3\baselineskip plus 0.2ex minus 0.1ex,parsep=0pt,topsep=0pt,align=left}
%indent for items-------------------------------------------
\setlist[enumerate]{leftmargin=\parindent,align=left,labelwidth=\parindent,labelsep=0em}%
\setlist[itemize]{leftmargin=0.5\parindent,align=left,labelwidth=0.5\parindent,labelsep=0em}

%%%define a new quotation%%%%%%%%%%%%%%%%%%%%%%
\makeatletter
\renewenvironment{quotation}
{\list{}{\listparindent 2em%equal to \parindent
        \partopsep   0.3\baselineskip plus 0.2ex minus 0.1ex%equal to \parskip
        \topsep   0em%here
        \itemindent   2em%equal to \parindent
        \rightmargin   2em%equal to \parindent
        \leftmargin   2em%equal to \parindent
        \parsep   0.3\baselineskip plus 0.2ex minus 0.1ex%equal to \parskip
    }%
    \item\relax}
{\endlist}
\makeatother

\begin{document}

\lipsum[1][1-3]
\begin{quotation}
\lipsum[2][1-3]
\end{quotation}
\lipsum[3][1-3]
\begin{enumerate}
\item \lipsum[4][1-3]
\item \lipsum[5][1-3]
\begin{quotation}
\lipsum[6][1-3]
\end{quotation}
\lipsum[7][1-3]
\end{enumerate}
\end{document}

如你所见，enumerate 环境中第一个引号前后的空格是合适的，而 enumerate 环境中第二个引号前后的空格是不合适的。那么如何达到下列目标？

1. 枚举内外引号前后的空格相同；
2. 引号前后的空格都等于\parskip。

Answer 1

试试这个代码。在环境中使用时，它会在引号环境前后添加空格enumerate。

使用环境\parskip中的定义list来更改引号前后的空格。

\documentclass{article}
\usepackage{lipsum,indentfirst}
\setlength{\parindent}{2em}
\setlength{\parskip}{0.3\baselineskip plus 0.2ex minus 0.1ex}

%%%enumerate and so on%%%%%%%%%%%%%%%%%%%%%%%
\usepackage{enumitem}
%space for items--------------------------------------------
\setenumerate[1,2,3]{itemsep=0pt,partopsep=0.3\baselineskip plus 0.2ex minus 0.1ex,parsep=0pt,topsep=0pt}
\setitemize[1,2,3]{itemsep=0pt,partopsep=0.3\baselineskip plus 0.2ex minus 0.1ex,parsep=0pt,topsep=0pt,align=left}
\setdescription{itemsep=0pt,partopsep=0.3\baselineskip plus 0.2ex minus 0.1ex,parsep=0pt,topsep=0pt,align=left}
%indent for items-------------------------------------------
\setlist[enumerate]{leftmargin=\parindent,align=left,labelwidth=\parindent,labelsep=0em}%
\setlist[itemize]{leftmargin=0.5\parindent,align=left,labelwidth=0.5\parindent,labelsep=0em}

%%%define a new quotation%%%%%%%%%%%%%%%%%%%%%%
\renewenvironment{quotation}
{\par\list{}{% changed <<<<<<<<<<
        \setlength{\parskip}{0.5\baselineskip plus 0.2ex minus 0.1ex}% use this <<<<<<<<<<<<
        \setlength{\partopsep}{\parskip}%       
        \setlength{\parsep}{\parskip}%
        \setlength{\topsep}{0em}%
        \setlength{\leftmargin}{2em}%
        \setlength{\rightmargin}{2em}%
        \setlength{\itemindent}{2em}%       
    } 
    \item[]}
{\endlist}

\begin{document}
    
    \lipsum[1][1-3]
    \begin{quotation}
        \lipsum[2][1-3]
    \end{quotation}
    \lipsum[3][1-3]
    \begin{enumerate}
        \item \lipsum[4][1-3]
        \item \lipsum[5][1-3]
        \begin{quotation}
            \lipsum[6][1-3]
        \end{quotation}
        \lipsum[7][1-3]
    \end{enumerate}

    \lipsum[1][1-3]
\end{document}

选项使用 LaTeXquotation环境，定义为：

\renewenvironment{quotation}{\list{}{%
        \listparindent 20pt%
        \itemindent\listparindent%
        \rightmargin\leftmargin}%
    \item[]}
{\endlist}

---

\documentclass{article}
\usepackage{lipsum,indentfirst}
\setlength{\parindent}{2em}
\setlength{\parskip}{0.3\baselineskip plus 0.2ex minus 0.1ex}

%%%enumerate and so on%%%%%%%%%%%%%%%%%%%%%%%
\usepackage{enumitem}
%space for items--------------------------------------------
\setenumerate[1,2,3]{itemsep=0pt,partopsep=0.3\baselineskip plus 0.2ex minus 0.1ex,parsep=0pt,topsep=0pt}
\setitemize[1,2,3]{itemsep=0pt,partopsep=0.3\baselineskip plus 0.2ex minus 0.1ex,parsep=0pt,topsep=0pt,align=left}
\setdescription{itemsep=0pt,partopsep=0.3\baselineskip plus 0.2ex minus 0.1ex,parsep=0pt,topsep=0pt,align=left}
%indent for items-------------------------------------------
\setlist[enumerate]{leftmargin=\parindent,align=left,labelwidth=\parindent,labelsep=0em}%
\setlist[itemize]{leftmargin=0.5\parindent,align=left,labelwidth=0.5\parindent,labelsep=0em}

\begin{document}
    
    \lipsum[1][1-3]
    \begin{quotation}
        \lipsum[2][1-3]
    \end{quotation}
    \lipsum[3][1-3]
    \begin{enumerate}
        \item \lipsum[4][1-3]
        \item \lipsum[5][1-3]
        \begin{quotation}
            \lipsum[6][1-3]
        \end{quotation}
        \lipsum[7][1-3]
    \end{enumerate}

    \lipsum[1][1-3]
\end{document}