Btukfyl

I created a course summary box. In order to distinguish the summaries by school year, I have put an optional argument that displays the latter in the upper left corner (highlighted in yellow on the screenshot).

To display this school year, I write a fraction in the optional argument, like this:

begin{resume}[$sfrac{2018}{2019}$]{chapitre 1}

tcbsubtitle{Définition}



lipsum[1]

end{resume}

In order to simplify the code and also to progress in LaTeX, I want to modify this argument to transmit only the year 2018, then automatically calculate the next school year and display the fraction 2018/2019.

To do this, I created a counter called annee,

%setcounter{annee}{#1}

but when I try to use it in a tcolorbox, I have this error:

! Missing endcsname
inserted.

documentclass{article}

usepackage{lipsum}

usepackage{xfrac}

usepackage[most]{tcolorbox}



newcounter{annee}



tcbset{titreresume/.style={boxed title style={colframe=black!15,colbacktitle=gray!75,

leftrule=1.5mm,rightrule=1.5mm,toprule=1.5pt,bottom=0pt,boxsep=1pt}}}



tcbset{soustitre/.style={subtitle style={colback=black!7,colframe=black!25,

boxsep=1mm,fontupper={sffamilybfserieslargeselectfontcolor{black!63}}}}}



newtcolorbox[auto counter]{resume}[2]{%

%setcounter{annee}{#1}

minipage boxed title*=-106mm,

before upper={textcolor{black!63}{#1 hfill   #2hfillthetcbcounter/pageref{nombre-de-page}}},

titreresume,soustitre,colframe=black!25,colback=white,leftrule=3mm,rightrule=3mm,toprule=2pt,bottomrule=2pt,left=3pt,right=0pt,top=3mm,

fonttitle=sffamilybfserieslarge,label={nombre-de-page},

enhanced,nobeforeafter,lower separated=false,attach boxed title to top center={yshift=-3mm,xshift=-linewidth/5},

title={normalsize Résumé}}



begin{document}



begin{resume}[$sfrac{2018}{2019}$]{chapitre 1}

tcbsubtitle{Définition}



lipsum[1]

end{resume}



newpage



begin{resume}[$sfrac{2018}{2019}$]{chapitre 1}



tcbsubtitle{Propriétés}

lipsum[2]

end{resume}

end{document}

How do I do calculations with a LaTeX counter in a tcolorbox?

Translated with www.DeepL.com/Translator

Well you can't set the counter in the middle of a key-val-list. But beside this you don't need a counter for this:

documentclass{article}

usepackage{lipsum}

usepackage{xfrac}

usepackage[most]{tcolorbox}





tcbset{titreresume/.style={boxed title style={colframe=black!15,colbacktitle=gray!75,

leftrule=1.5mm,rightrule=1.5mm,toprule=1.5pt,bottom=0pt,boxsep=1pt}}}



tcbset{soustitre/.style={subtitle style={colback=black!7,colframe=black!25,

boxsep=1mm,fontupper={sffamilybfserieslargeselectfontcolor{black!63}}}}}



newtcolorbox[auto counter]{resume}[2][0]{%

minipage boxed title*=-106mm,

before upper={textcolor{black!63}{sfrac{#1}{thenumexpr#1+1} hfill   #2hfillthetcbcounter/pageref{nombre-de-page}}},

titreresume,soustitre,colframe=black!25,colback=white,leftrule=3mm,rightrule=3mm,toprule=2pt,bottomrule=2pt,left=3pt,right=0pt,top=3mm,

fonttitle=sffamilybfserieslarge,label={nombre-de-page},

enhanced,nobeforeafter,lower separated=false,attach boxed title to top center={yshift=-3mm,xshift=-linewidth/5},

title={normalsize Résumé}}



begin{document}



begin{resume}[2018]{chapitre 1}

tcbsubtitle{Définition}



lipsum[1]

end{resume}



newpage



begin{resume}[2018]{chapitre 1}



tcbsubtitle{Propriétés}

lipsum[2]

end{resume}

end{document}