使用可选参数 Latex 中的新环境

Question

我在 Latex 中定义了两个新环境（nmlist 和 nmlistf），如下所示。前者创建一个在第一行由 \paragraph 引入的标题的列表，后者创建一个从第一行开始没有任何标题的列表。我应该如何修改前者，以便除了它自己的输出之外，它还可以用于创建与后者类似的输出？感谢您的贡献！

这是代码：

\documentclass[final,3p,times]{elsarticle}
\usepackage{enumitem}

\newenvironment{nmlist}[1]{% list with title
  \paragraph{#1}
  \begin{enumerate}[align=parleft,itemsep=-4pt,labelwidth=20mm,leftmargin=22mm]}
  {\end{enumerate}}

\newenvironment{nmlistf}{% list without title
  \begin{enumerate}[align=parleft,itemsep=-4pt,labelwidth=20mm,leftmargin=22mm]}
  {\end{enumerate}}


\begin{document}

 % With a title at the first line and with a list starting at the second line 
 \begin{nmlist}{Others}
  \item[{$a$}]{distances to x-axis}%
  \item[{$b$}]{distances to y-axis}%
 \end{nmlist}

 % Without a title and with a list starting at the first line
 \begin{nmlistf}
  \item[{$a$}]{distances to x-axis}%
  \item[{$b$}]{distances to y-axis}%
 \end{nmlistf}

\end{document}

Answer 1

\documentclass[final,3p,times]{elsarticle}
\usepackage{enumitem}

\newenvironment{nmlist}[1][]{% list with title
  \ifstrempty{#1}{}{\paragraph{#1}}%
  \begin{enumerate}[align=parleft,itemsep=-4pt,labelwidth=20mm,leftmargin=22mm]}
  {\end{enumerate}}

\begin{document}

 % With a title at the first line and with a list starting at the second line 
 \begin{nmlist}[Others]
  \item[{$a$}] distances to x-axis
  \item[{$b$}] distances to y-axis
 \end{nmlist}

 % Without a title and with a list starting at the first line
 \begin{nmlist}
  \item[{$a$}] distances to x-axis
  \item[{$b$}] distances to y-axis
 \end{nmlist}

\end{document}