Verbatim Text Inside Environment which is inside a Boolean Condition

Question

My code looks like this

\documentclass{article}
\usepackage{environ}

\newcommand{\showsolution}{1}
\NewEnviron{mysolution}{
\if\showsolution1
    \fbox{\BODY}
\fi}

\begin{document}

\begin{mysolution}
    \begin{verbatim}
       code code code
    \end{verbatim}
 \end{mysolution}

 \end{document}

where the solution environment is created with the NewEnviron package as I want to display the solution depending on an if statement. However, if I now want to put code inside my solution by using verbatim I get the runaway argument / Paragraph ended before \next was complete. Edit: with the MWE above the error changes to missing \item. However, commenting out the verbatim inside the error disappears so it is still the same issue eventhough the error changed.

I guess the solution is something similar to the fragile option in beamer's frame environment but I dont know wether there are similar options for the environ package. So how can I place verbatim text (or at least code) inside an if statement?

Answer 1

Thanks for all the replies. The suggestion by Steven was very nice however had the disadvantage that one would need multiple boxes (which have to be defined outside the actual solution environment) if one wished to write text between code snippets.

Another way is the lstinline command from the listings package. It works inside the solution environment and one can at least write inline code. But this packages offers another command, lstinputlisting which allows to display code from an external file. One can then specify with the options firstline and lastline which sections of the code one wants to display. Disadvantage of that approach is of course 1) one needs an additional file and 2) adding or deleting code requires to adjust the first/lastline options

\documentclass{article}
\usepackage{environ}
\usepackage{listings}
\usepackage{filecontents}
\begin{filecontents*}{ThisMWEasFile}
 1 blah &$ blah !
 2 Blah!@
 3 blah &$ blah @
 4 Blah!@
 5 blah &$ blah #
 6 Blah!@
 7 blah &$ blah $
 8 Blah!@
 9 blah &$ blah %
10 Blah!@
11 blah &$ blah ^
12 Blah!@
13 blah &$ blah &
14 Blah!@
15 blah &$ blah *
16 Blah!@
\end{filecontents*}

\newif\ifshowsolution
\showsolutiontrue

\NewEnviron{mysolution}{
\ifshowsolution
    \BODY
\fi}

\begin{document}
\begin{itemize}

    \item[Question 1:] Question with solution.\\
        \begin{mysolution}
            \lstinputlisting[firstline=1, lastline=5]{ThisMWEasFile.tex}
        \end{mysolution}
    \item[Question 2:] Question with solution.\\
        \begin{mysolution}
            \lstinputlisting[firstline=6, lastline=10]{ThisMWEasFile.tex}
            \textbf{text text text}
            \lstinputlisting[firstline=11, lastline=15]{ThisMWEasFile.tex}
        \end{mysolution}
\end{itemize}
\end{document}

Answer 2

With the scontents package it is very easy to achieve what you are looking for. Everything stored in memory including the content verbatim. If you want you can also save the content to external files using the key write-env=file.tex. I modified your example file a bit, the output is the same :)

\documentclass{article}
\usepackage[store-env=solutions]{scontents}
%\newif\ifshowsolution
%\showsolutiontrue
%\ifshowsolution
\setupsc{print-env=true}
%\fi
\pagestyle{empty}
\begin{document}
\begin{itemize}

\item[Question 1:] Question with solution.\\
\begin{scontents}
\begin{verbatim}
 1 blah &$ blah !
 2 Blah!@
 3 blah &$ blah @
 4 Blah!@
 5 blah &$ blah #
\end{verbatim}
\end{scontents}
\item[Question 2:] Question with solution.\\
\begin{scontents}
\begin{verbatim}
6 Blah!@
7 blah &$ blah $
8 Blah!@
9 blah &$ blah %
10 Blah!@
\end{verbatim}
\textbf{text text text}
\begin{verbatim}
11 blah &$ blah ^
12 Blah!@
13 blah &$ blah &
14 Blah!@
15 blah &$ blah *
16 Blah!@
\end{verbatim}
\end{scontents}
\end{itemize}
\end{document}

Answer 3

Another option is to use the exam document class. With the solution environment you write your solutions and with the answers option you determine that you want your solutions to be printed out.

Answer 4

As pointed out by others, verbatim content cannot be processed as the argument to a macro. Here, however, the verbatimbox package allows verbatim content to be placed (unprinted) into a LaTeX box that can be later recalled by way of macro. Then, you can use the if condition to determine whether or not to execute the macro containing the verbatim content.

\documentclass{article}
\usepackage{verbatimbox}
\newif\ifsoln
\begin{document}
\begin{myverbbox}{\solutionA}
\code #$code code
\end{myverbbox}
Here, 
\solntrue
\ifsoln
\fbox{\solutionA}
\fi
is printed, whereas here,
\solnfalse
\ifsoln
\fbox{\solutionA}
\fi
it is not printed, based on an if condition.
\end{document}

Trying to employ the form of the OP's question, this might be useful:

\documentclass{article}
\usepackage{environ,verbatimbox}

\newif\ifshowsolution
\NewEnviron{mysolution}{
\ifshowsolution
    \fbox{\BODY}
\fi}

\begin{document}
\showsolutiontrue
\begin{verbbox}
code code code
\end{verbbox}

Here it shows:
\begin{mysolution}
    \theverbbox
\end{mysolution}

\showsolutionfalse
Here it does not:
\begin{mysolution}
    \theverbbox
\end{mysolution}

 \end{document}