Bug in package answers?

Question

I have this slight variation of an example from the answers package

\documentclass[12pt,a4paper]{article}
\usepackage{ifthen}
\usepackage{answers}
\Newassociation{sol}{Solution}{ans}
\newboolean{InSol}\setboolean{InSol}{False}
\newenvironment{Sol}
% Need to know whether we are in a solution or not
% So we set a defined boolean to test this
{\setboolean{InSol}{True}\begin{sol}}
%
{\end{sol}\setboolean{InSol}{False}}

\begin{document}
\Opensolutionfile{ans}[ans1]

First exercise

\begin{Sol}
  First solution.
\end{Sol}

Second exercise

\begin{Sol}
  Second solution.
\end{Sol}
 \Closesolutionfile{ans}
 \section{Solutions}
 \input{ans1}
 \end{document}

And it produces following answer file

\begin{Solution}{}

First solution.

\end{Sol}

Second exercise

\begin{Sol}

Second solution.

\end{Sol}
 \Closesolutionfile{ans}
 \section{Solutions}
 \input{ans1}
 \end{document}

Is this a bug or am I doing something stupid?

Answer 1

You should not use \begin{sol} and \end{sol} in the definition of the environment, but \sol and \endsol. There's no need to reset the conditional to false, because the grouping provided by the environment will do it.

\documentclass[12pt,a4paper]{article}
\usepackage{ifthen}
\usepackage{answers}

\Newassociation{sol}{Solution}{ans}

\newboolean{InSol}\setboolean{InSol}{false}
\newenvironment{Sol}
% Need to know whether we are in a solution or not
% So we set a defined boolean to test this
  {\setboolean{InSol}{true}\sol}
  {\endsol}

\begin{document}
\Opensolutionfile{ans}[\jobname ans]

First exercise

\begin{Sol}
  First solution.
\end{Sol}

Second exercise

\begin{Sol}
  Second solution.
\end{Sol}
 \Closesolutionfile{ans}
 \section{Solutions}
 \input{\jobname ans}
 \end{document}

Contents of the answers file

\begin{Solution}{}
  First solution.
\end{Solution}
\begin{Solution}{}
  Second solution.
\end{Solution}