关于dashrule宏包画虚线的一个问题

你可以定义一个近似 dash 命令，

\ExplSyntaxOn
\NewDocumentCommand \approxhdashrule { O{0pt} m m m }
  {
    \hbox_to_wd:nn {#2}
      {
        \int_set:Nn \l_tmpa_int 
          { 
            2 * \int_div_round:nn { \int_value:w \tex_dimexpr:D #2 } 
                                  { 2 * \int_value:w \tex_dimexpr:D #4 } + 1 
          }
        \dim_set:Nn \l_tmpa_dim { \dim_eval:n {#2} / \l_tmpa_int }
        \hdashrule [#1] {#2} {#3} { \l_tmpa_dim }
        \hbox_overlap_left:n { \rule [#1] { \l_tmpa_dim } {#3} }
      }
  }
\ExplSyntaxOff

在尾部附加了一个 \rule。不过只能使用单个长度，不能使用不等长的（比如 1mm 2mm 1mm）。
由于在盒子中，自带了一个组，所以无需显式使用 \begingroup ... \endgroup。

\documentclass{article}
\usepackage{dashrule}
\setlength{\parindent}{0mm}
\begin{document}
\rule[0mm]{\linewidth}{1mm}
\hdashrule[0.5ex]{\linewidth}{0.5pt}{5mm}%

\hdashrule[0.5ex]{\linewidth}{0.5pt}{3mm}%

\hdashrule[0.5ex]{\linewidth}{0.5pt}{2mm}%

\hdashrule[0.5ex]{\linewidth}{0.5pt}{1mm}%

approximate:

\ExplSyntaxOn
\NewDocumentCommand \approxhdashrule { O{0pt} m m m }
  {
    \hbox_to_wd:nn {#2}
      {
        \int_set:Nn \l_tmpa_int 
          { 
            2 * \int_div_round:nn { \int_value:w \tex_dimexpr:D #2 } 
                                  { 2 * \int_value:w \tex_dimexpr:D #4 } + 1 
          }
        \dim_set:Nn \l_tmpa_dim { \dim_eval:n {#2} / \l_tmpa_int }
        \hdashrule [#1] {#2} {#3} { \l_tmpa_dim }
        \hbox_overlap_left:n { \rule [#1] { \l_tmpa_dim } {#3} }
      }
  }
\ExplSyntaxOff

\rule[0mm]{\linewidth}{1mm}

\approxhdashrule[0.5ex]{\linewidth}{0.5pt}{5mm}%

\approxhdashrule[0.5ex]{\linewidth}{0.5pt}{3mm}%

\approxhdashrule[0.5ex]{\linewidth}{0.5pt}{2mm}%

\approxhdashrule[0.5ex]{\linewidth}{0.5pt}{1mm}%

\end{document}