Generating table rows where the number of rows depends on a counter

Question

This question arises from this one that was specific to the exam document class, but there should, I imagine, be wider applicability here as well as usefulness outside of using exam.

\documentclass[10pt,addpoints]{exam}

\newcounter{magicrownumbers}
\newcommand\rownumber{\stepcounter{magicrownumbers}\arabic{magicrownumbers}}

\begin{document}

\begin{questions}
\question Question one.

\question Question two.

\question Question three.
\end{questions}

\bgroup
\def\arraystretch{2.5}
{\setlength{\tabcolsep}{2em}
\begin{tabular}{|c|c|c|c|}
\hline
Problem & Understood & Confused & \phantom{someemptytext}Note\phantom{someemptytext} \\
\hline
\rownumber & {} & {} & {}\\
\hline
\rownumber & {} & {} & {}\\
\hline
\rownumber & {} & {} & {}\\
\hline
\end{tabular}}
\egroup\\

Total number of questions: \numquestions. 

\end{document}

I used help from this question for the row numbers, but it seems like there should be an easy workaround for what I am trying to accomplish here. The table is how I would like it to look except I want the number of rows generated to be dictated by \numquestions from the exam class. As can be seen from the code, all \numquestions rows (3 in this case) are of the type

\rownumber & {} & {} & {}\\
\hline

Is there a way I can use \numquestions to make a table generate \numquestions rows of the type above?

Answer 1

The last value of question is still known when the questions environment ends, until a new one starts.

You can build a table based on this.

\documentclass[10pt,addpoints]{exam}
\usepackage{xparse,tabularx}

\ExplSyntaxOn
\tl_new:N \l__farlow_grading_tl
\NewDocumentCommand{\gradingtable}{}
 {
  \tl_clear:N \l__farlow_grading_tl
  \int_step_inline:nnnn { 1 } { 1 } { \value{question} }
   {
    \tl_put_right:Nn \l__farlow_grading_tl
     {
      ##1 \vphantom{$\bigg|$} & & & \\ \hline
     }
   }
  \par\noindent
  \begin{tabularx}{\textwidth}
   {
    | c |
    >{\hsize=0.5\hsize} X |
    >{\hsize=0.5\hsize} X |
    >{\hsize=2.0\hsize} X |
   }
  \hline
  Problem &
  \multicolumn{1}{c|}{Understood} &
  \multicolumn{1}{c|}{Confused} &
  \multicolumn{1}{c|}{Note} \\ \hline
  \tl_use:N \l__farlow_grading_tl
  \multicolumn{4}{@{}l}{{\small Number~of~problems:~\thequestion}}
  \end{tabularx}
 }
\ExplSyntaxOff

\begin{document}

\begin{questions}

\question Question one.

\question Question two.

\question Question three.

\end{questions}

\gradingtable

\end{document}

For placing the table above the questions (requires two runs to synchronize):

\documentclass[10pt,addpoints]{exam}
\usepackage{xparse,tabularx,refcount,etoolbox}

\newcounter{grading}
\BeforeBeginEnvironment{questions}{%
  \stepcounter{grading}%
  \gradingtable
}
\AfterEndEnvironment{questions}{%
  \addtocounter{question}{-1}%
  \refstepcounter{question}%
  \label{grading\thegrading @label}%
}

\ExplSyntaxOn
\tl_new:N \l__farlow_grading_tl
\NewDocumentCommand{\gradingtable}{}
 {
  \tl_clear:N \l__farlow_grading_tl
  \int_step_inline:nnnn { 1 } { 1 } { \getrefnumber{grading\thegrading @label} }
   {
    \tl_put_right:Nn \l__farlow_grading_tl
     {
      ##1 \vphantom{$\bigg|$} & & & \\ \hline
     }
   }
  \par\noindent
  \begin{tabularx}{\textwidth}
   {
    | c |
    >{\hsize=0.5\hsize} X |
    >{\hsize=0.5\hsize} X |
    >{\hsize=2.0\hsize} X |
   }
  \hline
  Problem &
  \multicolumn{1}{c|}{Understood} &
  \multicolumn{1}{c|}{Confused} &
  \multicolumn{1}{c|}{Note} \\ \hline
  \tl_use:N \l__farlow_grading_tl
  \multicolumn{4}{@{}l}{{\small Number~of~problems:~\getrefnumber{grading\thegrading @label}}}
  \end{tabularx}
 }
\ExplSyntaxOff

\begin{document}

\begin{questions}

\question Question one.

\question Question two.

\question Question three.

\end{questions}

\begin{questions}

\question Question one again.

\question Question two again.

\end{questions}

\end{document}

Answer 2

Constructing table rows within loops is 'difficult' due to grouping. expl3 helps here with \prg_replicate:nn which replicates the same content according to the first argument, which is \number\value{numquestions}.

I additionally used the new R columntype that automatically counts the lines, but this can be shifted to the macro \displaytherows as well.

\documentclass[10pt,addpoints]{exam}

\usepackage{expl3}
\usepackage{array}

\newcolumntype{R}{>{\stepcounter{magicrownumbers}\themagicrownumbers}c}

\newcounter{magicrownumbers}
\newcommand\rownumber{\stepcounter{magicrownumbers}\arabic{magicrownumbers}}

\ExplSyntaxOn
\makeatletter
\newcommand{\displaytherows}{%
  \prg_replicate:nn {\exam@numquestions}{ & {} & {} & {} \tabularnewline \hline}
}
\makeatother
\ExplSyntaxOff

\begin{document}


\begin{questions}
\question Question one.

\question Question two.

\question Question three.
\end{questions}

\bgroup
\def\arraystretch{2.5}
{\setlength{\tabcolsep}{2em}
  \begin{tabular}{|R|c|c|c|}
    \hline
    \multicolumn{1}{|c}{Problem} & Understood & Confused & \phantom{someemptytext}Note\phantom{someemptytext} \tabularnewline
    \hline
    \displaytherows
  \end{tabular}
}
\egroup

Total number of questions: \numquestions. 

\end{document}