Problem with expansion in expl3

Question

I have a problem with the following code. Although I manage to write the number of the week in front of the corresponding Monday, I am unable to use this number to write if the week in question is a member of a given list of weeks.

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{tikz}
\usepackage{xparse,expl3}
\usetikzlibrary{calendar}
\usepackage[landscape,margin=.5cm]{geometry}

\ExplSyntaxOn
\NewDocumentCommand{\pgfcalendarcurrentweek}{}
{
    \pgfcalendardatetojulian{\pgfcalendarcurrentyear-01-01}{\l_tmpb_int}
    \int_eval:n{(\pgfcalendarcurrentjulian-\l_tmpb_int)/7+1}
}

\begin{document}

\seq_new:N\g_foo_weeks_seq
\seq_set_from_clist:Nn\g_foo_weeks_seq{36,38}

%Calendrier
\begin{tikzpicture}
    \calendar[
        dates=17-09-01 to 17-09-30,
        name=cal,
        execute~at~begin~day~scope=
        {
            % each day is shifted down according to the day of month
            \pgftransformyshift{-.5*\pgfcalendarcurrentday cm}
        },
        day~code=
        {
            \node[name=\pgfcalendarsuggestedname,every~day,shape=rectangle,minimum~height=.5cm, text~width =.5cm]{\tikzdaytext};
            \draw[anchor=west] (0,3pt) node{\pgfcalendarweekdayshortname{\pgfcalendarcurrentweekday}};
            \ifdate{Monday}
            {
                \node[circle,gray,inner~sep=0,anchor=east] at (-.7cm,3pt) {\pgfcalendarcurrentweek};
            }{}

            % The following part does not work as I intend
            \ifdate{Tuesday}
            {
                \cs_generate_variant:Nn\seq_if_in:NnTF {NfTF}
                \seq_if_in:NxTF\g_foo_weeks_seq\pgfcalendarcurrentweek
                {
                    \node[circle,gray,inner~sep=0,anchor=east] at (-.7cm,3pt) {Yes};
                }
                {
                    \node[circle,gray,inner~sep=0,anchor=east] at (-.7cm,3pt) {No};
                }
            }
        }
    ];
\end{tikzpicture}
\ExplSyntaxOff

\end{document}

Answer 1

you need something that expands to an integer week number, not something that makes a complicated sequence of assignments and then finally typesets such a number.

One way is to follow the model of

\pgfcalendardatetojulian{\pgfcalendarcurrentyear-01-01}{\l_tmpb_int}

where the value of the calculation is placed in a macro which can be used to expand to the number.

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{tikz}
\usepackage{xparse,expl3}
\usetikzlibrary{calendar}
\usepackage[landscape,margin=.5cm]{geometry}
\errorcontextlines1000
\ExplSyntaxOn
\NewDocumentCommand{\pgfcalendarcurrentweek}{}
{
    \pgfcalendardatetojulian{\pgfcalendarcurrentyear-01-01}{\l_tmpb_int}
    \tl_set:Nx\l_current_week_int{\int_eval:n{(\pgfcalendarcurrentjulian-\l_tmpb_int)/7+1}}
}

                \cs_generate_variant:Nn\seq_if_in:NnTF {NfTF}

\begin{document}

\seq_new:N\g_foo_weeks_seq
\seq_set_from_clist:Nn\g_foo_weeks_seq{36,38}

%Calendrier
\begin{tikzpicture}
    \calendar[
        dates=17-09-01 to 17-09-30,
        name=cal,
        execute~at~begin~day~scope=
        {
            % each day is shifted down according to the day of month
            \pgftransformyshift{-.5*\pgfcalendarcurrentday cm}
        },
        day~code=
        {
         %   \node[name=\pgfcalendarsuggestedname,every~day,shape=rectangle,minimum~height=.5cm, text~width =.5cm]{\tikzdaytext};
          %  \draw[anchor=west] (0,3pt) node{\pgfcalendarweekdayshortname{\pgfcalendarcurrentweekday}};
            \ifdate{Monday}
            {
                \node[circle,gray,inner~sep=0,anchor=east] at (-.7cm,3pt) {
\pgfcalendarcurrentweek
\l_current_week_int
                };
            }{}
            % The following part does not work as I intend
            \ifdate{Tuesday}
            {
\pgfcalendarcurrentweek
                \seq_if_in:NxTF\g_foo_weeks_seq\l_current_week_int
                {
                    \node[circle,gray,inner~sep=0,anchor=east] at (-.7cm,3pt) {Yes (\l_current_week_int)};
                }
                {
                    \node[circle,gray,inner~sep=0,anchor=east] at (-.7cm,3pt) {No (\l_current_week_int)};
                }
            }
        }
    ];
\end{tikzpicture}
\ExplSyntaxOff

\end{document}