Package xsim - print a list of exercises by Tag

Question

I want to have a file with exercises and at the end of the file, I want to print the exercises sorted by level (a tag i created with xsim).

Below what do not work, for obvious reason, \printcollection works with a collection, not with a tag, but I cannot figure out how to handle collections, without writing it for every exercise).

Connected question: is it possible to define the level by a number (eg. 1, 2 or 3) and print a the corresponding number of $\star$ in the exercise-header?

\documentclass{article}
\usepackage[no-files]{xsim}

\DeclareExerciseTagging{level}
\DeclareExerciseTagging{nom}

\DeclareExerciseEnvironmentTemplate{custom}
  {
    \par\bigskip
    \noindent\sffamily\textbf
      {%
        \XSIMmixedcase {\GetExerciseName}\nobreakspace
        \GetExerciseProperty{counter}%
        \IfExercisePropertySetT{level}
          { (\GetExerciseProperty{level}) }%
        \IfExercisePropertySetT{nom}
          { {\itshape\GetExerciseProperty{nom}} }%
      }\par\noindent%
  }
  {\par\medskip}

\DeclareExerciseType{exo}{
  exercise-env= exo ,
  solution-env = soln ,
  exercise-name = \XSIMtranslate{exercise} ,
  exercises-name = \XSIMtranslate{exercises} ,
  solution-name = \XSIMtranslate{solution} ,
  solutions-name = \XSIMtranslate{solutions} ,
  exercise-template = custom ,
  solution-template = custom , 
  exercise-heading = \subsection* ,
  solution-heading = \subsection*
}

\xsimsetup{
  level ={$\star$,$\star\star$, $\star\star\star$} ,
  solution/print=true,
  soln/print=true,
}

\begin{document}

Le cours...

\begin{exo}[nom=Suite de Syracuse]
  Exercice 1 - pas de niveau 
\end{exo}

Le cours...

\begin{exo}[level=$\star$, nom = Suite de Fibonacci]
  Exercice 2 - niveau 1
\end{exo}

Une remarque ....

\begin{exo}[level=$\star\star$]
  Exercice 3 - niveau 2
\end{exo}

\begin{exo}[level=$\star$]
  Exercice 4 - niveau 1
\end{exo}

Et on termine par quelque chose de plus difficile

\begin{exo}[level=$\star\star\star$]
  Exercice 5 - très dur - niveau 3
\end{exo}

Fin du cours.

\newpage
Feuille exercice

%\FeuilleExercices

Exercices simples
\printcollection{level=$\star$}

Exercices medians
\printcollection{level=$\star\star$}

Exercices complexes
\printcollection{level=$\star\star\star$}

\end{document}

Answer 1

Both is possible.

You can define a command to only print the exercises for a certain level like this:

\NewDocumentCommand\printlevel{m}{%
  \ForEachUsedExerciseByType{%
    \def\ExerciseType{##1}%
    \def\ExerciseID{##2}%
      \IfExercisePropertySetT{level}{%
        \ifnum\GetExerciseProperty{level}=#1
          \printexercise{exo}{##2}%
        \fi
      }%
  }%
}

And with expl3's \prg_replicate:nn { integer } { code } which places integer times code in the input stream you can easily output the number of \stars:

\documentclass{article}
\usepackage[french]{babel}
\usepackage[T1]{fontenc}
\usepackage[no-files]{xsim}

\ExplSyntaxOn
\newcommand*\replicate{\prg_replicate:nn}
\ExplSyntaxOff

\DeclareExerciseTagging{level}
\DeclareExerciseTagging{nom}

\DeclareExerciseEnvironmentTemplate{custom}
  {%
    \par\bigskip
    \noindent\sffamily\textbf
      {%
        \XSIMmixedcase{\GetExerciseName}\nobreakspace
        \GetExerciseProperty{counter}%
        \IfExercisePropertySetT{level}
          { ($\replicate{\GetExerciseProperty{level}}{\star}$) }%
        \IfExercisePropertySetT{nom}
          { {\itshape\GetExerciseProperty{nom}} }%
      }\par\noindent
  }
  {\par\medskip}

\DeclareExerciseType{exo}{
  exercise-env= exo ,
  solution-env = soln ,
  exercise-name = \XSIMtranslate{exercise} ,
  exercises-name = \XSIMtranslate{exercises} ,
  solution-name = \XSIMtranslate{solution} ,
  solutions-name = \XSIMtranslate{solutions} ,
  exercise-template = custom ,
  solution-template = custom , 
  exercise-heading = \subsection* ,
  solution-heading = \subsection*
}

\NewDocumentCommand\printlevel{m}{%
  \ForEachUsedExerciseByType{%
    \def\ExerciseType{##1}%
    \def\ExerciseID{##2}%
      \IfExercisePropertySetT{level}{%
        \ifnum\GetExerciseProperty{level}=#1
          \printexercise{exo}{##2}%
        \fi
      }%
  }%
}

\xsimsetup{
  level ={1,2,3} ,
  % level/ignore-untagged = false,
  % soln/print=true,
}

\begin{document}

Le cours...

\begin{exo}[nom=Suite de Syracuse]
  Exercice 1 - pas de niveau 
\end{exo}

Le cours...

\begin{exo}[level=1, nom = Suite de Fibonacci]
  Exercice 2 - niveau 1
\end{exo}

Une remarque ....

\begin{exo}[level=2]
  Exercice 3 - niveau 2
\end{exo}

\begin{exo}[level=1]
  Exercice 4 - niveau 1
\end{exo}

Et on termine par quelque chose de plus difficile

\begin{exo}[level=3]
  Exercice 5 - très dur - niveau 3
\end{exo}

Fin du cours.

\newpage
Feuille exercice

%\FeuilleExercices

Exercices simples
\printlevel{1}

Exercices medians
\printlevel{2}

Exercices complexes
\printlevel{3}

\end{document}