Can't use tasks to generate answer keys using xparse

Question

I tried to compile the following code, which I collect and modify from: Label an item of a 'randomized enumerate' written by @egreg.

\documentclass[12pt,a4paper]{article}
\usepackage{amsmath, mathptmx, amssymb}
\usepackage[left=1.5cm,right=1.5cm,top=1.5cm,bottom=1.5cm]{geometry}

%Shuffle Questions
\usepackage{xparse,environ}

\ExplSyntaxOn
\NewEnviron{randomlist}[1][]
 {
  \keys_set:nn { lucas/randomlist } { #1 }
  \lucas_randomlist:V \BODY
 }
\NewDocumentCommand{\answerkey}{}
 {
  \subsubsection*{Answer ~ key}
  \begin{tasks}[label = \arabic*.](10)
  \seq_map_inline:Nn \g_lucas_randomlist_answers_seq { \task ##1 }
  \end{tasks}
 }
\NewDocumentCommand{\ans}{}
 {
  \seq_gput_right:Nx \g_lucas_randomlist_answers_seq { \use:c { @currentlabel } }
 }

\keys_define:nn { lucas/randomlist }
 {
  environment .tl_set:N = \l__lucas_randomlist_env_tl,
  seed .code:n = \sys_gset_rand_seed:n { #1 },
 }

\seq_new:N \g_lucas_randomlist_answers_seq
\cs_new_protected:Nn \lucas_randomlist:n
 {
  \seq_set_split:Nnn \l__lucas_randomlist_items_seq { \item } { #1 }
  % discard the empty first item
  \seq_pop_left:NN \l__lucas_randomlist_items_seq \l_tmpa_tl
  \seq_shuffle:N \l__lucas_randomlist_items_seq
  \begin{\l__lucas_randomlist_env_tl}
  \item \seq_use:Nn \l__lucas_randomlist_items_seq { \item }
  \end{\l__lucas_randomlist_env_tl}
 }
\cs_generate_variant:Nn \lucas_randomlist:n { V }

\ExplSyntaxOff

\usepackage[inline]{enumitem}
\setlist[enumerate]{
    label = \textbf{Q \arabic*.},
    align = left,
    labelwidth = \parindent, 
    leftmargin = \parindent,
    style = standard
}

\usepackage{tasks}[newest]
\newcommand*\tasklabelformat[1]{\textbf{#1.}}
\settasks{
    item-indent = 2em,
    label-width = 1.5em,
    label-offset = 0.25em,
    label = \Alph*,
    label-format = \tasklabelformat
}

%=========================================================
\begin{document}
\begin{randomlist}[environment=enumerate, seed=1]
\item How many letters in the word ``Tea'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ \ans
        \task $2$
        \task $4$.
   \end{tasks}

\item How many letters in the word ``Hi'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ 
        \task $2$ \ans
        \task $4$.
   \end{tasks}

\item How many letters in the word ``Cake'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ 
        \task $2$
        \task $4$. \ans
   \end{tasks}

\item How many letters in the word ``Tree'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ 
        \task $2$
        \task $4$. \ans
   \end{tasks}

\item How many letters in the word ``Dog'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ \ans
        \task $2$ 
        \task $4$.
   \end{tasks}

\item How many letters in the word ``House'' ?
    \begin{tasks}(4)
        \task $2$
        \task $3$ 
        \task $5$ \ans
        \task $4$.
   \end{tasks}

\item How many letters in the word ``Tea'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ \ans
        \task $2$
        \task $4$.
   \end{tasks}

\item How many letters in the word ``Hi'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ 
        \task $2$ \ans
        \task $4$.
   \end{tasks}

\item How many letters in the word ``Cake'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ 
        \task $2$
        \task $4$. \ans
   \end{tasks}

\item How many letters in the word ``Tree'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ 
        \task $2$
        \task $4$. \ans
   \end{tasks}

\item How many letters in the word ``Dog'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ \ans
        \task $2$ 
        \task $4$.
   \end{tasks}

\item How many letters in the word ``House'' ?
    \begin{tasks}(4)
        \task $2$
        \task $3$ 
        \task $5$ \ans
        \task $4$.
   \end{tasks}
\end{randomlist}
\answerkey
\end{document}

It pops the below structure and answer keys are not generated.

You've placed (tasks)(tasks) \seq_map_inline:Nn \g_lucas_randomlist_answers_seq
(tasks) {\task ##1} (tasks)(tasks) before the first \task

When I replace a corresponding part of the code by:

\NewDocumentCommand{\answerkey}{}
 {
  \subsubsection*{Answer ~ key}
  \begin{enumerate*}[nosep, label = \arabic*., mode = unboxed]
  \seq_map_inline:Nn \g_lucas_randomlist_answers_seq {\item \makebox[2cm][l]{##1}}
  \end{enumerate*}
 }

It works fine, but two lines of answer keys are not aligned as shown below:

How to solve that? Any solution is welcomed and I'll be very appreciated.

score 1 · Accepted Answer · answered May 24 '20 at 10:38

Environments from the tasks package need to see their body in order to be able to split the contents at each occurrence of \task and build the list according the chosen setup. This means you cannot build it on the fly within \begin{tasks} ... \end{tasks}. You need to build the environment body beforehand and then use it.

I suggest to modify the definition of \answerkey like this:

\cs_generate_variant:Nn \use:nn {nV}

\NewDocumentCommand \answerkey {}
  {
    \subsubsection* {Answer~ key}
    \tl_clear:N \l_tmpa_tl
    \seq_map_inline:Nn \g_lucas_randomlist_answers_seq
      { \tl_put_right:Nn \l_tmpa_tl { \task ##1 } }
    \use:nV
      { \begin{tasks}[label = \arabic*](10)}
      \l_tmpa_tl
    \end {tasks}
 }

\use:nn reads two arguments and puts them in the input stream. The variant \use:nV reads the contents of a variable as second argument and uses its contents as argument. Before we only need to build up the body of the tasks environment as contents of the variable.

BTW: with a sufficiently up to date xparse you can read the body of an environment using the argument type b which means you don't need environ. I modified the code accordingly:

\documentclass[12pt,a4paper]{article}
\usepackage{amsmath, mathptmx, amssymb}
\usepackage[left=1.5cm,right=1.5cm,top=1.5cm,bottom=1.5cm]{geometry}

%Shuffle Questions
\usepackage{xparse}

\ExplSyntaxOn
\NewDocumentEnvironment {randomlist} {o+b}
  {
    \IfNoValueF {#1} { \keys_set:nn { lucas/randomlist } {#1} }
    \lucas_randomlist:n {#2}
  }
  {}

\cs_generate_variant:Nn \use:nn {nV}

\NewDocumentCommand \answerkey {}
  {
    \subsubsection* {Answer~ key}
    \tl_clear:N \l_tmpa_tl
    \seq_map_inline:Nn \g_lucas_randomlist_answers_seq
      { \tl_put_right:Nn \l_tmpa_tl { \task ##1 } }
    \use:nV
      { \begin{tasks}[label = \arabic*](10)}
      \l_tmpa_tl
    \end {tasks}
 }

\NewDocumentCommand \ans {}
  {
    \seq_gput_right:Nx \g_lucas_randomlist_answers_seq
      { \use:c { @currentlabel } }
  }

\keys_define:nn { lucas/randomlist }
  {
    environment .tl_set:N = \l__lucas_randomlist_env_tl,
    seed .code:n = \sys_gset_rand_seed:n { #1 },
  }

\seq_new:N \g_lucas_randomlist_answers_seq
\cs_new_protected:Nn \lucas_randomlist:n
  {
    \seq_set_split:Nnn \l__lucas_randomlist_items_seq { \item } {#1}
    % discard the empty first item
    \seq_pop_left:NN \l__lucas_randomlist_items_seq \l_tmpa_tl
    \seq_shuffle:N \l__lucas_randomlist_items_seq
    \begin {\l__lucas_randomlist_env_tl}
      \item \seq_use:Nn \l__lucas_randomlist_items_seq { \item }
    \end {\l__lucas_randomlist_env_tl}
  }

\ExplSyntaxOff

\usepackage[inline]{enumitem}
\setlist[enumerate]{
    label = \textbf{Q \arabic*.},
    align = left,
    labelwidth = \parindent, 
    leftmargin = \parindent,
    style = standard
}

\usepackage{tasks}[newest]
\newcommand*\tasklabelformat[1]{\textbf{#1.}}
\settasks{
    item-indent = 2em,
    label-width = 1.5em,
    label-offset = 0.25em,
    label = \Alph*,
    label-format = \tasklabelformat
}

%=========================================================
\begin{document}
\begin{randomlist}[environment=enumerate, seed=1]
\item How many letters in the word ``Tea'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ \ans
        \task $2$
        \task $4$.
   \end{tasks}

\item How many letters in the word ``Hi'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ 
        \task $2$ \ans
        \task $4$.
   \end{tasks}

\item How many letters in the word ``Cake'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ 
        \task $2$
        \task $4$. \ans
   \end{tasks}

\item How many letters in the word ``Tree'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ 
        \task $2$
        \task $4$. \ans
   \end{tasks}

\item How many letters in the word ``Dog'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ \ans
        \task $2$ 
        \task $4$.
   \end{tasks}

\item How many letters in the word ``House'' ?
    \begin{tasks}(4)
        \task $2$
        \task $3$ 
        \task $5$ \ans
        \task $4$.
   \end{tasks}

\item How many letters in the word ``Tea'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ \ans
        \task $2$
        \task $4$.
   \end{tasks}

\item How many letters in the word ``Hi'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ 
        \task $2$ \ans
        \task $4$.
   \end{tasks}

\item How many letters in the word ``Cake'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ 
        \task $2$
        \task $4$. \ans
   \end{tasks}

\item How many letters in the word ``Tree'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ 
        \task $2$
        \task $4$. \ans
   \end{tasks}

\item How many letters in the word ``Dog'' ?
    \begin{tasks}(4)
        \task $1$
        \task $3$ \ans
        \task $2$ 
        \task $4$.
   \end{tasks}

\item How many letters in the word ``House'' ?
    \begin{tasks}(4)
        \task $2$
        \task $3$ 
        \task $5$ \ans
        \task $4$.
   \end{tasks}
\end{randomlist}
\answerkey
\end{document}

Thank for your quick reply. It works like a charm. I'm so grateful to you @cgnieder, this is the second time you help me out. — Nguyễn Xuân Duy Bảo, May 24 '20 at 10:45
hi @cgnieder again, is there anyway to set the start number inside randomlist environment, for example, if I want the number starts at 10? — Nguyễn Xuân Duy Bảo, Jul 30 '20 at 04:41

Can't use tasks to generate answer keys using xparse

1 Answers1