Asterisk in front of section in TOC

Question

There is this question Add an asterisk in front of section label in TOC asking to find a way to put an asterisk (*) in front of the title of a specific section in the table of contents.

The goal is to have something like this

For example 4.58 is not a hard problem, 4.60 is a hard problem and 4.65 is a very hard problem.

Alann Munn replied with this solution https://tex.stackexchange.com/a/16341/270421 but clarified that the asterisk also appears in the title of the section in the document (that would not be a real issue actually) and aslo in the marks in the headers:

Personally, I find it unattractive and want a solution to delete it.

So far, I tried to create a copy of the section environment by tweaking things like in Where can I find help files or documentation for commands like \@startsection for LaTeX? and by redefining a copy of the definition of the \part environment.

Answer 1

Try this

\documentclass{book}

\newcommand\maybeast{}% check definable

\let\maybeast\relax

\renewcommand\thesection{\maybeast\thechapter.\arabic{section}}

\newcommand\nextonewithast{%
   \addtocontents{toc}
   {\def\maybeast{\global\let\maybeast\relax\string\llap{*}}}%
}

\newcommand\nextonewithtwoasts{%
   \addtocontents{toc}
   {\def\maybeast{\global\let\maybeast\relax\string\llap{**}}}%
}


\begin{document}
\tableofcontents

\chapter{Test}
\section{section without asterisk}

\nextonewithast
\section{section with asterisk}
\section{section without asterisk}
\section{section without asterisk}

\chapter{Test 2}

\nextonewithast
\section{section with asterisk}

\nextonewithtwoasts
\section{section with two asterisks}
\section{section without asterisk}

\nextonewithast
\section{section with asterisk}

\end{document}

Answer 2

You can try the following code, which does not effect the section numbers in the section headings or the page headers.

\documentclass{book}

\usepackage{xpatch}
\xpatchcmd{\numberline}{#1}{\tocasts#1}{}{\PatchFailure}
\newcommand*{\tocasts}{}
\newcommand*{\nexttocasts}[1][1]{%
  \addtocontents{toc}{\activatetocasts{#1}}%
}
\makeatletter
\DeclareRobustCommand*{\activatetocasts}[1]{%
  \renewcommand*{\tocasts}{%
    \global\let\tocasts\@empty
    \makebox[0pt][r]{\@tempcnta=#1\relax\@whilenum\@tempcnta>\z@\do{%
        *\advance\@tempcnta\m@ne
      }}%
  }%
}
\makeatother

\begin{document}
\tableofcontents
\chapter{Test}
\section{One section without asterisk}
\nexttocasts
\newpage
Empty page
\newpage
As you can see here there is not problem with the page header.
\section{One section with one asterisk}
\nexttocasts[2]
\section{One section with two asterisks}
\section{Another section without asterisk}
\newpage

\end{document}

Note: The code could fail, e.g., if you are using a package or class, that changes the definition of \numberline. If so, please ask a new question with a proper minimal working example.

Answer 3

I propose an approach where you declare right before \tableofcontents which section numbers you want with an asterisk, as a comma separated list. The code uses only the old LaTeX kernel "\in@" technique, although I used for convenience \expanded tool which is available since 2019 only (except for lualatex which had it earlier), and one could easily reformat this.

Notice that in this interface \ActivateAsterisksFor is a one-shot command, each new use erases previous data, one could configure a cumulative one rather if you prefer.

Caveat: do not insert spaces in its argument; if you need to wrap on next line, use % to not create a space from end of line.

If you redefine \thesection, for example to use letters in place of digits, you need then to adjust argument of \ActivateAsterisksFor to be kept in sync.

Edited: initially I had overlooked you wanted also double asterisks for some. So here is original answer and below it edited answer.

method for only one or no asterisk

\documentclass{book}

\newtoks\asteriskedsections
\newcommand\ActivateAsteriskFor{\asteriskedsections}

\let\originalnumberline\numberline

\makeatletter
\renewcommand\numberline[1]{%
  \expanded{\noexpand\in@{,#1,}{,\the\asteriskedsections,}}%
  \ifin@\originalnumberline{\llap{*}#1}\else\originalnumberline{#1}\fi
}
\makeatother

\begin{document}
\ActivateAsteriskFor{1.2,2.1,2.2,2.4}
\tableofcontents
\chapter{Test}
\section{section without asterisk}
\section{section with asterisk}
\section{section without asterisk}
\section{section without asterisk}

\chapter{Test 2}
\section{section with asterisk}
\section{section with asterisk}
\section{section without asterisk}
\section{section with asterisk}

\end{document}

method for none, one, or two asterisks

\documentclass{book}


\newtoks\asteriskedsections
\newcommand\ActivateAsteriskFor{\asteriskedsections}

\newtoks\doublyasteriskedsections
\newcommand\ActivateTwoAsterisksFor{\doublyasteriskedsections}

\let\originalnumberline\numberline

\makeatletter
\renewcommand\numberline[1]{%
  \expanded{\noexpand\in@{,#1,}{,\the\doublyasteriskedsections,}}%
  \ifin@\originalnumberline{\llap{**}#1}\else
     \expanded{\noexpand\in@{,#1,}{,\the\asteriskedsections,}}%
     \ifin@\originalnumberline{\llap{*}#1}\else
     \originalnumberline{#1}\fi\fi
}
\makeatother

\begin{document}
\ActivateAsteriskFor{1.2,2.1,2.4}
\ActivateTwoAsterisksFor{2.2}
\tableofcontents
\chapter{Test}
\section{section without asterisk}
\section{section with asterisk}
\section{section without asterisk}
\section{section without asterisk}

\chapter{Test 2}
\section{section with asterisk}
\section{section with asterisk}
\section{section without asterisk}
\section{section with asterisk}

\end{document}