\documentclass[classical]{einfart}

\usepackage{ProjLib}

\usepackage[left indent]{multifootnote}

%%================================
%% For typesetting code
%%================================
\usepackage{listings}
\usepackage{xcolor}
\usepackage{setspace}
\definecolor{code-main}{RGB}{70,130,180}
\definecolor{code-expl3}{RGB}{240,50,60}
\definecolor{code-option}{RGB}{40,110,20}
\definecolor{code-keys}{RGB}{100,130,150}
\definecolor{code-comment}{RGB}{20,120,80}
\definecolor{code-background}{gray}{0.99}
\lstset{
    language = [LaTeX]TeX,
    basicstyle = \ttfamily,
    keywordstyle = \color{code-main},
    commentstyle = \color{code-comment},
    showstringspaces = false,
    breaklines = true,
    frame = lines,
    backgroundcolor = \color{code-background},
    flexiblecolumns = true,
    escapeinside = {(*}{*)},
    alsoletter = {_,:},
    % numbers = left,
    % firstnumber = last,
    numberstyle = \scriptsize\ttfamily,
    stepnumber = 1,
    numbersep = 5pt,
}
\newcommand{\meta}[1]{$\langle${\normalfont\itshape#1}$\rangle$}
\lstset{% LaTeX2 commands
    classoffset = 0,
    texcsstyle =* \color{code-main},
    moretexcs =
      {
        multifootnotetext,
        multifootnotemark,
        multifootnotetag,
        multifootnotetagtext,
        multifootnote,
        footnotenumber,
        footnotetag,
      }
}
\lstset{% LaTeX3 commands
    classoffset = 1,
    texcsstyle =* \color{code-expl3},
    moretexcs =
      {
      }
}
\lstnewenvironment{code}{\setstretch{1.05}\LocallyStopLineNumbers}{\ResumeLineNumbers\vspace{-.3\baselineskip}\vspace{-.5\parskip}}
\lstnewenvironment{code*}{\setstretch{1.05}\lstset{numbers=left}\LocallyStopLineNumbers}{\ResumeLineNumbers\vspace{-.3\baselineskip}\vspace{-.5\parskip}}

\newcommand{\packageoption}[1]{\texttt{\textcolor{code-option}{#1}}}
\newcommand{\commandoption}[1]{\texttt{\textcolor{code-keys}{#1}}}

%%================================
%% tip
%%================================
\usepackage[many]{tcolorbox}
\newenvironment{tip}[1][Tip]
  {%
    \LocallyStopLineNumbers%
    \begin{tcolorbox}[breakable,
        enhanced,
        width = \textwidth,
        colback = paper, colbacktitle = paper,
        colframe = gray!50, boxrule=0.2mm,
        coltitle = black,
        fonttitle = \sffamily,
        attach boxed title to top left = {yshift=-\tcboxedtitleheight/2, xshift=.5cm},
        boxed title style = {boxrule=0pt, colframe=paper},
        before skip = 3mm,
        after skip = 3mm,
        top = 2.5mm,
        bottom = 1.5mm,
        title={\scshape\sffamily #1}]%
  }
  {%
    \end{tcolorbox}%
    \ResumeLineNumbers%
  }


\newcommand{\multifootnotepackage}{{\normalfont\textsf{multifootnote}}}

\begin{document}

\def\PackageVersion{2022/05/31}

\title{\multifootnotepackage{}\\\smallskip\itshape Multiple numbers for the same footnote}
\author{Jinwen XU}
\thanks{Corresponding to: \texttt{\multifootnotepackage{} \PackageVersion}}
\date{\TheDate{\PackageVersion}[only-year-month], in Paris}

\maketitle

\begin{abstract}
    \raggedleft
    The package \multifootnotepackage{} provides two groups of commands for \\generating footnotes with multiple numbers (or marks, if you prefer).
\end{abstract}


\vspace*{-.5\baselineskip}

\section{How to load it}

You can simply load the current package with:

\begin{code}
\usepackage[(*\meta{options}*)]{multifootnote}
\end{code}

\medskip
It has the following options:
\begin{itemize}[label=,leftmargin=1.25em,itemindent=-1.25em]
    \item \packageoption{left align}
        \begin{itemize}
            \item Align the footnotes to the left.
            \item Alternative names: \packageoption{left-align} \,$|$\, \packageoption{leftalign}
        \end{itemize}
    \item \packageoption{left indent} or \packageoption{left indent} \lstinline|=| \meta{length}
        \begin{itemize}
            \item Similar to \packageoption{left align}, but with an indentation \meta{length}, default to be \texttt{1.5em}.
            \item Alternative names: \packageoption{left-indent} \,$|$\, \packageoption{leftindent}
        \end{itemize}
\end{itemize}

\section{How to use it}

Here are two approaches for producing a footnote with multiple numbers, and in either of them, there are two commands involved.

\subsection{First approach}

This approach is more or less traditional, with one command to produce the footnote mark and another the text.
\begin{itemize}
    \item \lstinline|\multifootnotemark[|\meta{label}\lstinline|]|
    \begin{itemize}
        \item This command is for producing the footnote marks.
        \item \meta{label} cannot contain commas. However, colon \textquote{\texttt{:}} and semicolon \textquote{\texttt{;}} are allowed.
        \item Alternative name: \lstinline|\footnotenumber[|\meta{label}\lstinline|]|.
    \end{itemize}
    \item \lstinline|\multifootnotetext[|\meta{list of labels}\lstinline|]{|\meta{footnote text}\lstinline|}|
    \begin{itemize}
        \item This command is for producing the footnote text.
        \item \meta{list of labels} is a list of labels that you specified with \lstinline|\multifootnotemark[|\meta{label}\lstinline|]|, separated with commas, like this: \commandoption{fn1,fn2,fn3}.
        \item It should not be too far away from the corresponding marks.
        \item Alternative name: \lstinline|\multifootnote[|\meta{list of labels}\lstinline|]{|\meta{footnote text}\lstinline|}|.
    \end{itemize}
\end{itemize}

\subsection{Second approach}

This approach is considered more convenient, with one command to specify the \meta{tag} while printing the footnote mark, and another to print the footnote text for this group.
\begin{itemize}
    \item \lstinline|\multifootnotetag{|\meta{tag}\lstinline|}| or \lstinline|\multifootnotetag{|\meta{list of tags}\lstinline|}|
    \begin{itemize}
        \item This command is for producing the footnote marks.
        \item \meta{tag} cannot contain commas. However, colon \textquote{\texttt{:}} and semicolon \textquote{\texttt{;}} are allowed.
        \item \meta{list of tags} is a list of tags, separated with commas, like this: \commandoption{fntag1,fntag2,fntag3}.
        \item Alternative name: \lstinline|\footnotetag{|\meta{tag}\lstinline|}| or \lstinline|\footnotetag{|\meta{list of tags}\lstinline|}|.
    \end{itemize}
    \item \lstinline|\multifootnotetagtext[|\meta{tag}\lstinline|]{|\meta{footnote text}\lstinline|}|
    \begin{itemize}
        \item This command is for producing the footnote text.
        \item It should not be too far away from the corresponding marks.
        \item Alternative name: \lstinline|\multifootnote[|\meta{tag}\lstinline|]{|\meta{footnote text}\lstinline|}|.
    \end{itemize}
\end{itemize}

\begin{tip}
    \lstinline|\multifootnote| appears in both approaches for producing footnote text: it shall be interpreted as \lstinline|\multifootnotetext| if the optional argument is a comma-separated list, and as \lstinline|\multifootnotetagtext| if not. See the examples below.
\end{tip}

\bigskip
\begin{center}
    \itshape
    If you're feeling confused, don't worry. Let's now take a look at some examples.
\end{center}


\section{Examples}

Here are two examples of usage, with the package option \textquote{\packageoption{left indent}} enabled.

\subsection{The first approach}

\medskip
\begin{code}
Lorem ipsum\footnotenumber[(*\commandoption{fn1}*)] dolor\footnotenumber[(*\commandoption{fn2}*)] sit amet\footnotenumber[(*\commandoption{fn3}*)], consectetur\footnotenumber[(*\commandoption{fn4}*)] adipiscing elit\footnotenumber[(*\commandoption{fn5}*)].
\multifootnote[(*\commandoption{fn1,fn2,fn5}*)]{This is a footnote for demonstration.}
\multifootnote[(*\commandoption{fn1,fn3,fn4}*)]{This is another footnote for demonstration.}
\end{code}

Result:

\fbox{Lorem ipsum\footnotenumber[fn1] dolor\footnotenumber[fn2] sit amet\footnotenumber[fn3], consectetur\footnotenumber[fn4] adipiscing elit\footnotenumber[fn5].}
\multifootnote[fn1,fn2,fn5]{This is a footnote for demonstration.}
\multifootnote[fn1,fn3,fn4]{This is another footnote for demonstration.}

\subsection{The second approach}

\medskip
\begin{code}
Lorem ipsum\footnotetag{(*\commandoption{fntag1,fntag2}*)} dolor\footnotetag{(*\commandoption{fntag1}*)} sit amet\footnotetag{(*\commandoption{fntag2}*)}, consectetur\footnotetag{(*\commandoption{fntag2}*)} adipiscing elit\footnotetag{(*\commandoption{fntag1}*)}.
\multifootnote[(*\commandoption{fntag1}*)]{This is a footnote for demonstration.}
\multifootnote[(*\commandoption{fntag2}*)]{This is another footnote for demonstration.}
\end{code}

Result:

\fbox{Lorem ipsum\footnotetag{fntag1,fntag2} dolor\footnotetag{fntag1} sit amet\footnotetag{fntag2}, consectetur\footnotetag{fntag2} adipiscing elit\footnotetag{fntag1}.}
\multifootnote[fntag1]{This is a footnote for demonstration.}
\multifootnote[fntag2]{This is another footnote for demonstration.}

\begin{tip}
    The second approach is more recommended, as it involves fewer labels, and you shall not need to worry about the order of footnote marks in \lstinline|\multifootnote|.
\end{tip}

\begin{tip}[Attention]
    Notice that in the first approach, \meta{label} appears as an optional argument of \lstinline|\footnotenumber[|\meta{label}\lstinline|]| (thus square brackets); while in the second approach, \meta{tag} is a mandatory argument of \lstinline|\footnotetag{|\meta{tag}\lstinline|}| (thus curly brackets).
\end{tip}


\bigskip
\section{Acknowledgement}

This package arises from a question (\href{https://tex.stackexchange.com/q/645330}{\texttt{645330}}) on \texttt{TeX.StackExchange}. The author thanks user \href{https://tex.stackexchange.com/users/270985}{\textsf{@Bolzano}} for bringing up the question of producing such footnotes.

The author thanks \href{https://tex.stackexchange.com/users/2388}{\textsf{Ulrike Fischer}} for the code for fixing the broken hyperlinks generated by the first approach, and user \href{https://tex.stackexchange.com/users/73317}{\textsf{@frougon}} for his kind and helpful suggestions and comments.

The author also wishes to thank user \href{https://tex.stackexchange.com/users/213149}{\textsf{@antshar}} for proposing the second approach. The code is surprisingly simple but works just as fine as that of the first approach.

\section{Known issues}

\begin{itemize}
    % \item When package \textsf{hyperref} is loaded, hyperlinks to those footnotes generated by the commands here cannot point to the correct place.
    \item \multifootnotepackage{} is not compatible with the package \textsf{footnotebackref}.
\end{itemize}

\medskip
If you run into any issue or have ideas for improvement, feel free to discuss on:
\begin{center}
    \url{https://github.com/Jinwen-XU/multifootnote/issues}
\end{center}
or email me via \href{mailto:ProjLib@outlook.com}{\texttt{ProjLib@outlook.com}}.

\end{document}