Automatic creation of lstlistings in AMC questions

Question

Context

I'm trying to get an automatic exam where I can generate random numbers (using pgfmathrandominteger) in the AMC package to create different questions using code (listings) and inputing these random numbers to the code. For example, change the value a variable will get, or change the number of iterations on a loop, etc.

Problem

However, the listing package is not easy to work with in the AMC environment (see How to expand a macro to use it inside a question in AMC?). Moreover, to add the random number that should appear on the code, and to be generated that number from the question is becoming a challenge.

For example, in the code below, I can generate the number ( \pgfmathrandominteger{\mynum}{1}{8}) but when using more questions it doesn't work (same happens when using more than one copy).

Ideally, I should generate the random number inside the question, so every time the question is parsed by AMC a new number is generated and then it should be parsed by the box. However, the box is already typeset when declared (as far as I understand). Thus, when I use it on the lstlisting code (if I could reach the \mynum macro) I still need to be able to reform that environment again and again.

How that behavior can be achieved?

\documentclass{article}
\usepackage[box]{automultiplechoice}
\usepackage{listings}
\usepackage{tikz}
\lstset{  escapeinside={@}{@}}
% a simple wrapper to create boxes automatically
\makeatletter
\newcounter{myboxcounter}
\newenvironment{mybox}{%
  \stepcounter{myboxcounter}%
  \expandafter\newsavebox\csname foobox\roman{myboxcounter}\endcsname
  \global\expandafter\setbox\csname foobox\roman{myboxcounter}\endcsname\hbox\bgroup\color@setgroup\ignorespaces
}{%
  \color@endgroup\egroup
}
\newcommand{\insertbox}{\stepcounter{myboxcounter}%
  \edef\name{foobox\roman{myboxcounter}}\edef\x{%
  \expandafter\usebox\csname\name\endcsname}\x}
\makeatother
\begin{document}
%%% preparation of the groups
\pgfmathrandominteger{\mynum}{1}{8}
\begin{mybox}
\begin{lstlisting}[language=C++]
  int a = @\mynum@;
  a = a + 10;
\end{lstlisting}
\end{mybox}
\element{code}{
  \begin{question}{code 1}
    Which is the result of \texttt{a} \mynum?
\insertbox
\begin{choices}
  \correctchoice{\pgfmathparse{\mynum+10}\pgfmathresult}
  \wrongchoice{20}
  \wrongchoice{0}
  \wrongchoice{30}
\end{choices}

\end{question}
}
%%% copies
\setcounter{myboxcounter}{0}
\onecopy{1}{% when changed the number of copies to more than one it won't work
\insertgroup{code}
}
\end{document}

Answer 1

You shouldn't use listings inside arguments, but if you are asking for troubles, another experimental workaround (explained in the documentation) is add a line feed (^^J) at the end of each line, escape \{}% characters and spaces. Unfortunately, then you can’t escape to LaTeX inside such listings (according to package documentation) so you have little chance of include here random values.

However, without listings (or using it only for immutable code) make mathematical problems with random values in AMC is easy using the fp package. A naïve example:

\documentclass{article}
\usepackage[box]{automultiplechoice}
\usepackage{fp}
\usepackage{amsmath}
\usepackage{listings}

\element{code}{
\begin{question}{sum}
\FPeval\Ra{trunc(1+random*8,0)}
\FPeval\Rb{trunc(4+random*5,0)}
\FPeval\RnoA{clip((Ra+1)/Rb)}
\FPeval\RnoB{clip(Ra*Rb+100)}
\FPeval\RnoC{clip(Ra-Rb+1)}
\FPeval\Ryes{clip(Ra+Rb)}
\begin{lstlisting}^^J
a ? b = c ^^J 
\end{lstlisting}
Check the equation with correct result ($c$) when $a = \Ra{}$ and $b = \Rb{}$?

\begin{choices}
\wrongchoice{   $\dfrac{\Ra{}}{\Rb{}} = \RnoA$}
\wrongchoice{   $\Ra{}^{\Rb{}} = \RnoB$}
\wrongchoice{   $\Ra{} - \Rb{} = \RnoC$}
\correctchoice{ $\Ra{} + \Rb{} = \Ryes$}
\end{choices}
\end{question}}

\lstset{basicstyle=\color{red!50!black}\bfseries\sffamily,frame=none} 

\begin{document}
\onecopy{2}{\insertgroup{code}}
\end{document}

Edit: OK, ok, you want the best of everything, no matther how complicated could be.

One dirty trick to surpass this problem is use \input{} for included code with macros inside. I am not sure how safe is this method, so use at your own risk. To modify the above example step by step:

1) Include an escape character

\lstset{escapechar=!, ....}

2) Cut the lstlisting environment, save it as chunk.tex, remove the line feeds (^^J) and insert the random values escaped:

\begin{lstlisting}
!\Ra\ ? \Rb\ = c  
\end{lstlisting}

3) Then insert \input{chunk} in the exam.

4) Compile and check the result:

Edit 2:

Another option could be try other methods of code listing. Check the Topic list­ing in CTAN. You mileage may vary depending of your aims about the format and the compatibility with AMC. For example, the package minted is algo good for code listing but seem also incompatible with the above MWE, whereas the package algpseudocode allow use a algorithmic environment that seem to work well inside the question and including the variables \Ra and \Rb:

\begin{algorithmic}[1]
\State $sum\gets \Ra$
\State $i\gets \Rb $
\While{$i\le n$}
\State $sum\gets sum+i$
\State $i\gets i+1$
\EndWhile
\end{algorithmic}