在环境中包装每个段落

Question

我正在尝试创建一个环境，将每个段落包装在不同环境中。例如，如果我将每个段落包装在flushleft其中，它将看起来像这样：

\documentclass{article}

\newcounter{conversationpar}
\newenvironment{conversation}{
    \setcounter{conversationpar}{0}
    \everypar={
        \refstepcounter{conversationpar}
        \ifnum\value{conversationpar}>1\end{flushleft}\fi
        \begin{flushleft}
    }
}{
    \end{flushleft}
}

\begin{document}
\begin{conversation}
Let her hang me: hee that is well hang'de in this world, needs to feare no colours.

Make that good.

He shall see none to feare.
\end{conversation}
\end{document}

这不起作用，但理论上我希望它产生与执行以下操作相同的结果：

\begin{flushleft}
Let her hang me: hee that is well hang'de in this world, needs to feare no colours.
\end{flushleft}

\begin{flushleft}
Make that good.
\end{flushleft}

\begin{flushleft}
He shall see none to feare.
\end{flushleft}

感谢您的帮助。

Answer 1

我不确定您最终希望如何使用它，但是此代码将conversation在每个部分中分割环境主体\par并将每个部分放置在flushleft环境内：

\documentclass{article}

\ExplSyntaxOn

% create a macro that will hold every paragraph of the evironment's body as a sequence
\seq_new:N \l__myconv_conversationpars_seq

% create a new environment macro, +b is a pseudo-argument that represents the body,
% the + denotes that the body may contain \pars,
% you can refer to the body using #1 (since it is the first argument statement)
\NewDocumentEnvironment{conversation} { +b } {

    % split the body (provided by #1) at every \par and 
    % store the single parts as sequence in the previously defined macro
    \seq_set_split:Nnn \l__myconv_conversationpars_seq { \par } { #1 } 

    % for each item in the sequence, place it inside a flushleft environment
    \seq_map_inline:Nn \l__myconv_conversationpars_seq { 
        \begin{flushleft} 
            ##1 
        \end{flushleft} 
    }
} { }

\ExplSyntaxOff

\begin{document}

\begin{conversation}
Let her hang me: hee that is well hang'de in this world, needs to feare no colours.

Make that good.

He shall see none to feare.
\end{conversation}

\end{document}

---

编辑

从评论中我了解到，您希望为您的环境提供两个额外的强制参数，并使用第一个或第二个，具体取决于当前项是奇数还是偶数。我将其添加到上面的代码中：

\documentclass{article}

\ExplSyntaxOn

\seq_new:N \l__myconv_conversationpars_seq

% add two mandatory arguments, the body now being the third argument 
\NewDocumentEnvironment{conversation} { m m +b } {
    \seq_set_split:Nnn \l__myconv_conversationpars_seq { \par } { #3 } 

    % for each item in the sequence, return index as ##1 and the item as ##2
    \seq_map_indexed_inline:Nn \l__myconv_conversationpars_seq { 
        \begin{flushleft} 
            % test whether the index is odd, 
            % if yes, use value of first mandatory argument stored in #1,
            % if not, use value of first mandatory argument stored in #2
            % (~ denotes a space)
            \int_if_odd:nTF { ##1 } { #1 } { #2 } : ~ 
            ##2 
        \end{flushleft} 
    }
} { }

\ExplSyntaxOff

\begin{document}

\begin{conversation}{odd}{even}
Let her hang me: hee that is well hang'de in this world, needs to feare no colours.

Make that good.

He shall see none to feare.
\end{conversation}

\end{document}