2

I want to be able to make \dotfill in math \begin{align*} mode

Here is my code

\documentclass{article}
\usepackage{amsmath}
\begin{document}

\begin{align*}
& M=E-e \sin E \makebox[5cm]{\dotfill} \tag{1}\\
& A=B+C
\end{align*}

\end{document}

But this does not work. I want the dots to go up to the tag (1) as in old typography. I also want that the dots do not move the equation. I want also the dots to fill automatically the space until the tag. Thanks for any help

Update 29/10/2022

I have now a macro that allows to just set the length of the dot sequence. But I would like to do it in an automated way.

\newcommand{\jdot}[1]{ \rlap{\makebox[#1]{\dotfill} }}

Now my LateX code becomes

\documentclass{article}
\usepackage{amsmath}
\newcommand{\jdot}[1]{ \rlap{\makebox[#1]{\dotfill} }}
\begin{document}

\begin{align*}
 M&=E-e \sin E \jdot{4.4cm} \tag{1}\\
 A&=B+C
\end{align*}

\end{document}

The dot sequence do not move the equation, thanks to the rlap but I still need to define manually the length of the sequence. The challenge is to find this length in an automated way.

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1 Answer 1

Reset to default
1

I have learned a solution from the CTeX-org forum. After a few modifications, the code is as follows:

\documentclass{article}
\usepackage{amsmath}
\usepackage{zref-savepos}

\makeatletter
\ExplSyntaxOn

\zref@require@unique

\NewDocumentCommand { \dotstag } { O{} m }
  {
    \mode_if_math:TF
      { \@@_math_cdotfill:n { (#2) } }
      { \__examzh_cdotfill: (#2) }
    \mode_if_math:F
      {
        \par \noindent \ignorespaces
      }
  }
% 仿照 latex.ltx, line 651 的 \dotfill
\cs_new:Npn \__examzh_cdotfill:
  {
    \mode_leave_vertical:
    \cleaders \hb@xt@ .44em {\hss $\cdot$ \hss} \hfill
    \kern\z@
  }

\cs_new_protected:Npn \@@_math_cdotfill:n #1
  {
    \stepcounter { zref@unique }
    \hbox_overlap_right:n
      {
        \zsaveposx { \thezref@unique L }
        \zref@ifrefundefined { \thezref@unique R }
          { }
          {
            \cleaders
              \hbox_to_wd:nn { .44em } { \hss $\cdot$ \hss }
              \skip_horizontal:n
                {
                    \zposx { \thezref@unique R } sp
                  - \zposx { \thezref@unique L } sp
                }
          }
      }
    \tag * { \zsaveposx { \thezref@unique R } #1 }
  }

\ExplSyntaxOff
\makeatother

\begin{document}

Test with \verb|\dotstag{}|:
\begin{align*}
    M & = E - e \sin E \dotstag{1} \\
    A & = B + C \dotstag{2}
\end{align*}

\end{document}

Note that you should compile twice to get the desired result. By the way, the \dotstag command can also be used in the text mode!

enter image description here

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3
  • This is great Stephen !! Commented Oct 29, 2022 at 15:29
  • This is great Stephen !! Exactly what I needed. At first I thought it did not work. Then I read that one needs to compile twice. The first time you dont have the dots. The second time everything is in place. I must say I am not sufficiently expert in TeX to understand the code. Its quite complicated. We will see if someone comes with something simpler, but meanwhile, it fulfils entirely the requirement. Thanks again. Commented Oct 29, 2022 at 15:35
  • @Jacques Glad that this method helps. And I am looking forward to more interesting solutions for this problem. Commented Oct 29, 2022 at 16:30

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