How to defer content to a later part of the document?

Question

I want to create a collection of problems, each problem consisting of the problem itself, optional hints and optional solutions. I wanted to know what would be the best way to do it ?

I could use some help defining an interface that let's me lay down the problems at one place, and print the according hints in different parts (or chapters) for hints and solutions, respectively.

I have been hinted, that package exsheets could be halfway to the solution.

\documentclass{report} 
\usepackage[english]{babel} 
\usepackage{mathtools} 
\usepackage{blindtext} 

\numberwithin{equation}{section} 
\numberwithin{figure}{section} 
\numberwithin{table}{section} 

\newcounter{problem}
\newenvironment{problem}[1]{
{\bfseries\large{#1}\par}
}{}
\begin{document}
\part{Problems}
\section{Puzzle 1}
\begin{problem}{Pythagoras}
\blindtext
%\begin{hints}
%   \blindtext
%\end{hints}
%\begin{solution}
%   \blindtext
%\end{solution}
\end{problem}
\section{Puzzle 2}

\part{Hints}
\section{Puzzle 1 hint}
\section{Puzzle 2 hint}

\part{Solutions}
\section{Puzzle 1 solution}
\section{Puzzle 2 solution}

\end{document}

I also asked this question at LaTeX community.

Answer 1

Like you say in your question: this is doable with exsheets:

\documentclass{article}
\usepackage[english]{babel}
\usepackage{blindtext}

\usepackage{exsheets}

\SetupExSheets{ headings = block-subtitle }

% new property `hint':
\DeclareQuestionProperty{hint}

% a command to print all given hints
\NewDocumentCommand\printquestionhints{}{%
  \ForEachQuestion
    {%
      \IfQuestionPropertyT{hint}{##1}{%
        \ExSheetsHeading
          {block}               % headings style
          {Hint}                % heading
          {\QuestionNumber{##1}}% number
          {0}                   % points -- need to be zero here
          {0}                   % bonus points -- need to be zero here
          {##1}%                % ID
        \GetQuestionProperty{hint}{##1}%
        \par
        \medskip
      }%
    }%
}

\begin{document}

\section{Problems}
\begin{question}[subtitle=Pythagoras]
  This is the first problem.
  \SetQuestionProperties{ hint = This is a hint to the first problem. }
\end{question}
\begin{solution}
  This is the solution to the first problem.
\end{solution}

\begin{question}[subtitle=Another Problem]
  This is the second problem.
\end{question}
\begin{solution}
  This is the solution to the second problem.
\end{solution}

\begin{question}[subtitle=Yet Another Problem]
  This is the third problem.
  \SetQuestionProperties{ hint = This is a hint to the third problem. }
\end{question}
\begin{solution}
  This is the solution to the third problem.
\end{solution}

\section{Hints}
\printquestionhints

\section{Solutions}
\printsolutions

\end{document}

Customizations are possible (font shape/size of the headings, ...)

Answer 2

Store the hints and solutions in a storage bin.

\documentclass{article}
\usepackage[english]{babel}
\usepackage{mathtools}
\usepackage{environ}

\numberwithin{equation}{section}
\numberwithin{figure}{section}
\numberwithin{table}{section}

\newcounter{problem}
\newenvironment{problem}[1]
 {\refstepcounter{problem}%
  {\textbf{Problem \theproblem\ (#1)}\par}\nopagebreak\noindent\ignorespaces}
 {}

\makeatletter
\newtoks\late@hintstoks
\newtoks\late@solutiontoks

\NewEnviron{hints}{%
  \toks@=\expandafter{\BODY}%
  \protected@edef\@tempa{%
    \the\late@hintstoks % the previous contents
    \noexpand\late@hint{\theproblem}{\the\toks@}%
  }%
  \global\late@hintstoks=\expandafter{\@tempa}%
}
\NewEnviron{solution}{%
  \toks@=\expandafter{\BODY}%
  \protected@edef\@tempa{%
    \the\late@solutiontoks % the previous contents
    \noexpand\late@solution{\theproblem}{\the\toks@}%
  }%
  \global\late@solutiontoks=\expandafter{\@tempa}%
}
\newcommand{\late@hint}[2]{%
  \paragraph*{Hints for problem #1}#2%
}
\newcommand{\late@solution}[2]{%
  \subsubsection*{Solution for problem #1}#2%
}

\newcommand{\printhints}{%
  \part{Hints}
  \the\late@hintstoks
}
\newcommand{\printsolutions}{%
  \part{Solutions}
  \the\late@solutiontoks
}
\makeatother

\begin{document}

\part{Problems}
\section{Puzzle 1}
\begin{problem}{Pythagoras}
This problem is about Pythagoras' theorem
\begin{hints}
These are the hints about Pythagoras.
\end{hints}
\begin{solution}
Pythagoras' theorem is easy!
\end{solution}
\end{problem}
\section{Puzzle 2}
\begin{problem}{Riemann}
Prove the zeros of the $\zeta$ functions are on the critical line.
\begin{hints}
Try first with a few cases.
\end{hints}
\begin{solution}
Oh, well!
\end{solution}
\end{problem}

\printhints

\printsolutions

\end{document}

Answer 3

tcolorbox is not devoted to create problems+solution collections but can be used for it.

Next code is almost copied from tcolorbox documentation. It shows an example using savelowerto and recording tools: record, \tcbstartrecording, \tcbstoprecording, \tcbinputrecords.

savelowerto saves lower box part for further processing. In this case all solutions are declared in lower parts which are recorded and later on readed with \tcbinputrecords.

\documentclass{article}

\usepackage{lipsum}
\usepackage[most]{tcolorbox}

\NewTColorBox[auto counter,number within=section]{exercise}{+O{}}{ %
enhanced,colframe=green!20!black,colback=yellow!10!white,coltitle=green!40!black,
fonttitle=\bfseries,
underlay={\begin{tcbclipinterior}
\shade[inner color=green!80!yellow,outer color=yellow!10!white]
(interior.north west) circle (2cm);
\draw[help lines,step=5mm,yellow!80!black,shift={(interior.north west)}]
(interior.south west) grid (interior.north east);
\end{tcbclipinterior}},
title={Exercise~\thetcbcounter:},
label={exercise@\thetcbcounter},
attach title to upper=\quad,
after upper={\par\hfill\textcolor{green!40!black} %
{\itshape Solution on page~\pageref{solution@\thetcbcounter}}},
lowerbox=ignored,
savelowerto=solutions/exercise-\thetcbcounter.tex,
record={\string\solution{\thetcbcounter}{solutions/exercise-\thetcbcounter.tex}},
#1
}
\NewTotalTColorBox{\solution}{mm}{ %
enhanced,colframe=red!20!black,colback=yellow!10!white,coltitle=red!40!black,
fonttitle=\bfseries,
underlay={\begin{tcbclipinterior}
\shade[inner color=red!50!yellow,outer color=yellow!10!white]
(interior.north west) circle (2cm);
\draw[help lines,step=5mm,yellow!80!black,shift={(interior.north west)}]
(interior.south west) grid (interior.north east);
\end{tcbclipinterior}},
title={Solution of Exercise~\ref{exercise@#1} on page~\pageref{exercise@#1}:},
phantomlabel={solution@#1},
attach title to upper=\par,
}{\input{#2}}
\tcbset{no solution/.style={no recording,after upper=}}

\begin{document}
\section{Some problems}

\tcbstartrecording

\lipsum[1]
\begin{exercise}
Compute the derivative of the following function:
\begin{equation*}
f(x)=\sin((\sin x)^2)
\end{equation*}
\tcblower
The derivative is:
\begin{align*}
f’(x) &= \left( \sin((\sin x)^2) \right)’
=\cos((\sin x)^2) 2\sin x \cos x.
\end{align*}
100\end{exercise}

\lipsum[2]
\begin{exercise}[no solution]
It holds:
\begin{equation*}
\frac{d}{dx}\left(\ln|x|\right) = \frac{1}{x}.
\end{equation*}
\end{exercise}

\lipsum[3]
\begin{exercise}
Compute the derivative of the following function:
\begin{equation*}
f(x)=(\sin(\sin x))^2
\end{equation*}
\tcblower
The derivative is:
\begin{align*}
f’(x) &= \left( (\sin(\sin x))^2 \right)’
=2\sin(\sin x)\cos(\sin x)\cos x.
\end{align*}
\end{exercise}

\tcbstoprecording

\section{Some solutions to previous problems}

\tcbinputrecords

\end{document}