I would like to use the answers package to create exercises and answers
(printed in different parts of the document). The exercises should refer to the
solutions with a margin note (via marginnote) and the other way around. The
MWE below already works quite well but I couldn't figure out how to define my
own solutions environment (see 'FAILS'). It should be like the exercise
environment, just with label 'Solution' instead of 'Exercise'.
\documentclass{scrreprt}
\usepackage[american]{babel}
\usepackage{mathtools}
\usepackage{amsthm}
\usepackage{thmtools}
\usepackage{etoolbox}
\usepackage{marginnote}
\usepackage{answers}
\usepackage{hyperref}
\declaretheoremstyle[%
spaceabove=0.5em,
spacebelow=0.5em,
headfont=\sffamily\bfseries,
notefont=\sffamily\bfseries,
notebraces={(}{)},
headpunct={},
bodyfont=\normalfont%
]{mythmstyle}
\declaretheorem[style=mythmstyle, numberwithin=chapter]{exercise}
% \declaretheorem[style=mythmstyle, sibling=exercise]{solution}% => FAILS
\Newassociation{solution}{sol}{solutions}
\begin{document}
\Opensolutionfile{solutions}
\section{Section 1}
\begin{Filesave}{solutions}
\clearpage
\section{Solutions Section 1}
\end{Filesave}
\begin{exercise}[Header 1]\label{exlabel1}\marginnote{Sol.\ p.~\pageref{sollabel1}}\par\noindent
First exercise
\begin{solution}[Header 1]\label{sollabel1}\marginnote{Ex.\ p.~\pageref{exlabel1}}\par\noindent
First solution.
\end{solution}
\end{exercise}
\clearpage
\section{Section 2}
\begin{Filesave}{solutions}
\clearpage
\section{Solutions Section 2}
\end{Filesave}
\begin{exercise}[Header 2]\label{exlabel2}\marginnote{Sol.\ p.~\pageref{sollabel2}}\par\noindent
\begin{enumerate}
\item Part 1
\item Part 2
\end{enumerate}
\begin{solution}[Header 2]\label{sollabel2}\marginnote{Ex.\ p.~\pageref{exlabel2}}
\begin{enumerate}
\item Solution Part 1
\item Solution Part 2
\end{enumerate}
\end{solution}
\end{exercise}
\Closesolutionfile{solutions}
\clearpage
\input{solutions}
\end{document}
The final goal would be to not having to set the labels and margin notes
manually. One idea is to manually define the exercise and solution environments
and to pass the same 'base label' to each of them as an argument. These two
environments then create a label for the exercise and one for its solution
and refer to each other. I tried that in a different post (see
Page number hyperlinks (exercises to solutions: fail; solutions to exercises: ok))
but wasn't too successful yet.
Update
Here is how far I got with the ideas on Adding another answer hyperlinked to the question itself
\documentclass{scrreprt}
\usepackage[american]{babel}
\usepackage{mathtools}
\usepackage{amsthm}
\usepackage{thmtools}
\usepackage{etoolbox}
\usepackage{marginnote}
\usepackage{answers}
\usepackage{hyperref}
\newcounter{counter}
\numberwithin{counter}{section}
\makeatletter
\newenvironment{exercise}[2][]{\refstepcounter{counter}\par% #1 = header; #2 = label
\normalfont\topsep6\p@\@plus6\p@\relax
\trivlist
\labelsep 0pt
\def\mysollabel{#2}
\preto\mysollabel{sol:}
\def\myexlabel{#2}
\preto\myexlabel{ex:}
\item[\hskip\labelsep\sffamily\bfseries Exercise~\thecounter\ #1]\label{\myexlabel}% this '\label' correctly refers to the exercise
\marginnote{Solution p.~\pageref{\mysollabel}}%
\ignorespaces%
}{%
\endtrivlist\@endpefalse
}
\makeatother
\Opensolutionfile{solutions}
\Newassociation{solution}{Soln}{solutions}
\begin{document}
\section{Section 1}
\begin{Filesave}{solutions}
\clearpage
\section{Solutions Section 1}
\end{Filesave}
\begin{exercise}[Header 1]{ex:1:label}
First exercise
\begin{solution}[Header 1]{ex:1:label}
First solution.
\end{solution}
\end{exercise}
\clearpage
\section{Section 2}
\begin{Filesave}{solutions}
\clearpage
\section{Solutions Section 2}
\end{Filesave}
\begin{exercise}[Header 2]{ex:2:label}
\begin{enumerate}
\item Part 1
\item Part 2
\end{enumerate}
\begin{solution}[Header 2]{ex:2:label}
\begin{enumerate}
\item Solution Part 1
\item Solution Part 2
\end{enumerate}
\end{solution}
\end{exercise}
\Closesolutionfile{solutions}
% Renew the solution environment so that it hyperlinks back to the exercise
\makeatletter
\renewenvironment{Soln}[2][]{\par% #1 = header; #2 = label
\normalfont\topsep6\p@\@plus6\p@\relax
\trivlist
\labelsep 0pt
\def\myexlabel{#2}
\preto\myexlabel{ex:}
\def\mysollabel{#2}
\preto\mysollabel{sol:}
\item[\hskip\labelsep\sffamily\bfseries Solution~\ref{\myexlabel}\ #1]\hypertarget{\mysollabel}{}%
\marginnote{\hyperlink{\myexlabel}{Exercise p.~\pageref{\myexlabel}}}%
\ignorespaces%
}%
{%
\popQED\endtrivlist\@endpefalse
}%
\makeatother
\clearpage
\IfFileExists{solutions.tex}{\input{solutions.tex}}{}
\end{document}
Best Answer
From my Update I tried to improve the code. I realized that
Solnneeds to have three arguments and I made them all formal/required arguments so thatanswerscan work with them (this part originally failed). I didn't need to usehyperlinkspecifically (the links turned out correctly). I'll convert this MWE into the original document and see whether everything still works (I'll report back if not). Feel free to comment on possible improvements of the code.