# How can I produce exercises in one part of a LaTeX document with selected answers in another?

How can I produce exercises in one part of a LaTeX document with selected answers in another? I could, of course, simply typeset the questions and the answers separately, but this is too likely lead to divergence in the labels for the questions and the answers as the document is edited.

What I'd really like is a command that would allow me to typeset exercises at the point at which the command was used and which took an optional argument for a solution to be stored until a final section (chapter, or part) "Selected Exercise Answers". I'd like the questions (and the selected answers) to be labeled in the output by Chapter.Section.Question or even Chapter.Question.

-

You can use the exam document class in both your documents. Then refer to chapter 8: including solutions.

Basically, anywhere in the document you can just specify \printanswers or \noprintanswers or use the answers option when loading the document class.

It’s easiest if you have the actual questions and answers in a separate document that you \input into both the exercise document and the sample solution document.

If you want an extra section with the answers, you could instead \input the questions document twice, once before and once after the \printanswers document: this will cause the first appearance of the questions to be printed without answers, and the second appearance with answers.

-

The answers package appears to do something like this (do texdoc answers, or the equivalent on your platform, for the documentation).

If that doesn't work, or isn't really suitable, then I've got a hand-rolled solution to exactly this problem which I could post here.

(duplicated from a stackoverflow question)

OK: Sam Nead, in the comments, wanted to see the hand-rolled version, so I've included it in part below. The comments report an inheritance from Victor Eijkhout's comment.sty, but he's not to blame for the way I've butchered it. This isn't complete, as it doesn't show the output file being read in at the end. It illustrates that if you want to write out stuff with backslashes, you might have to do entertaining things with catcodes. Certainly, I learned a few things from examining and adapting Eijkhout's code.

No warranty expressed or implied; contents may settle during handling; do not ingest; and keep well out of the reach of children.

%%% {examples} environment -- problem/example, to be collected at the end
%
% \if@examples is a flag to tell us if we've seen any examples yet.
\newif\if@examples \@examplesfalse
\newwrite\@exampleaux
\@definecounter{example}
%
% Don't use \newenvironment.  Instead use the fact that \begin{env}
% turns into \begingroup\env .  This code is simplified from
% Eijkhout's comment.sty
%
% The \@bsphack...\@esphack pair doesn't seem to want to work, here
% (well, it does in horizontal, but not in vertical, mode).
%
% The {example} environment takes an optional argument, giving the
% number of dangerousbend symbols to attach to the example.  The
% default is zero (negative numbers are treated the same as zero,
% numbers larger than about 2 are probably silly, but will work).
%
% Unfortunately, because of the \@ifnextchar, and the fact that the
% contents of this environment are processed oddly, you can't have
% anything expandable immediately after the \begin{example}, unless
% you write \begin{example}[0] or \begin{example}\relax.
%
% The end of the environment must be \end{example} alone on a line
% (ie, no whitespace before or after).  The same is true for the
% beginning and end of the {examplenotes} environment.
%
\def\makeother#1{\catcode#1=12 }
\def\example{\@bsphack\@ifnextchar[%]
\@example{\@example[0]}}
% \@openexamples opens the examples file.  Nilpotent.
\def\@openexamples{%
\if@examples \else
\immediate\openout\@exampleaux\jobname.examples%
\immediate\write\@exampleaux{\relax}%
\global\@examplestrue
\fi
}
\def\theexample{\@arabic\c@example}
\def\@example[#1]{%
\@openexamples
\refstepcounter{example}%
% Read in contents line by line, with all catcodes other'
\let\do\makeother \dospecials %
\makeother\^^L%
\endlinechar\^^M \catcode\^^M=12 %
\immediate\write\@exampleaux %
{\string\begin{examplebody}%
{\theexample}%
{\csname the\LN@currsectionlevel\endcsname}%
{#1}%
}%
\if@screenpdf %
\else %
\marginpar{\small{See example \theexample}}%
\fi %
\@tempswatrue
\ProcessExampleLine %
}
%
% Define \EndExampleTest, with all catcodes other
{\escapechar=-1 \xdef\EndExampleTest{\string\\end\string\{example\string\}}}
{\escapechar=-1 \xdef\BeginNotesTest{\string\\begin\string\{examplenotes\string\}}}
{\escapechar=-1 \xdef\EndNotesTest{\string\\end\string\{examplenotes\string\}}}
% Write out the body of the {example}, carefully surrounding the
% content of the {examplenotes} environment with
% \ifexamplenotes...\fi.  Note this _requires_ that the beginning and
% end of the {examplenotes} environment appear on lines by
% themselves.  Change the escape character so that we can write out
% \if..\fi without problems.
{\catcode\^^M=12 \endlinechar=-1 \catcode\|=0 |catcode|\=12 %
|gdef|ProcessExampleLine#1^^M{|def|test{#1}%
|if@tempswa
|immediate|write|@exampleaux{\ifexampletext}|@tempswafalse
|fi
|ifx|BeginNotesTest|test %
|immediate|write|@exampleaux{\fi\ifexamplenotes}%
|fi %
|ifx|EndExampleTest|test %
|edef|next{%
|immediate|write|@exampleaux{\fi\end{examplebody}}%
|@esphack %
|endgroup %
}%
|else %
|immediate|write|@exampleaux{#1}%
|ifx|EndNotesTest|test %
|immediate|write|@exampleaux{\fi\ifexampletext}%
|fi %
|let|next|ProcessExampleLine %
|fi %
|next}%
}

% Add text to the examples file
\@openexamples
{\@temptokena{#1}%
\immediate\write\@exampleaux{\the\@temptokena}}}

-
Sure, but I took the spirit of the area51 faq to apply: Don't worry about whether a question might be asked on another site. Your goal is to make the best possible site for this community. – vanden Jul 27 '10 at 8:26
I read that prescription a different way. No problem: I'll copy the other answer over here. – Norman Gray Jul 27 '10 at 8:40
I reverted my down vote. – vanden Jul 27 '10 at 8:53
I'm interested to see the hand-rolled solution. – Sam Nead Mar 7 '11 at 11:37

My ExSheets package is designed for exactly this purpose. It gives you the possibility to print the answers to the exercises all at once, selected by section or chapter, or print them by question ID. The example below assumes that every exercise has an answer but that's actually not necessary.

One could also collect all the exercises and their solutions in a seperate file (or maybe one file per part?) and include selected exercises where they should be input. This of course still means that the answers could be printed selectively.

\documentclass{book}
\usepackage{exsheets}
\SetupExSheets{
% question numbering: »chapter.question«
% use ch.se.qu' for »chapter.section.question«
counter-format = ch.qu
}
% the previous paragraph a littler larger than the default:
{
join   = { title[r,B]number[l,B](1ex,0pt) } ,
attach =
{
main[l,vc]title[l,vc](0pt,0pt) ;
main[r,vc]points[l,vc](\marginparsep,0pt)
},
above  = \baselineskip-.5ex ,
below  = .5ex
}

\usepackage{kantlipsum}

\begin{document}
\chapter{One}\exlabel{chap:one}
\section{One A}
\kant[2]

\begin{question}[ID=one:a]
Question of section one a.
\end{question}
\begin{solution}
Solution to the question one a.
\end{solution}

\section{One B}
\kant[3]

\begin{question}[ID=one:b]
Question of section one b.
\end{question}
\begin{solution}
Solution to the question one b.
\end{solution}

\chapter{Two}\exlabel{chap:two}
\section{Two A}
\kant[4]

\begin{question}[ID=two:a]
Question of section two a.
\end{question}
\begin{solution}
Solution to the question two a.
\end{solution}

\section{Two B}
\kant[5]

\begin{question}[ID=two:b]
Question of section two b.
\end{question}
\begin{solution}
Solution to the question two b.
\end{solution}

\printsolutions
% or select by ID:
% \printsolutions[byID={one:a,two:b}]
% or select by chapter:
% \printsolutions[chapter=\exref{chap:two}]

\end{document}

-
Awesome package, Clemens! :) – Paulo Cereda Oct 20 '12 at 0:08
Thanks, Paulo! :) – clemens Oct 20 '12 at 7:24
@cgnieder Can I use your package in Vietnamese? How can I rename 'Question' and 'Solution'? – minthao_2011 Nov 2 '14 at 11:38
@minthao_2011 There are two possibilities both described in the manual: a) there are options to set the names manually b) there is a way to add translations that will be used if the babel language is chosen. – clemens Nov 3 '14 at 12:17
@cgnieder I used \usepackage[vietnam]{babel}, but the Questions and the Solutions did not translate. – minthao_2011 Nov 3 '14 at 16:06

Strange that nobody mentioned the exercise package. See the following example, in which the answers are 'created' just after the exercises, but only printed later in the second section. Things like difficulty level, exercise header, etc. can all be defined.

\documentclass{article}

\begin{document}
\section{Questions}
Here are some questions:
\begin{Exercise}[title={First question}]
This is the first exercise.
\end{Exercise}

\begin{Exercise}[title={Second question},difficulty=3]
Questions number two, without an anwer.
\end{Exercise}

\begin{Exercise}[title={Third question}]
Question number three, this one has an answer again.
\end{Exercise}

\end{document}

-

If you can't find a LaTeX package to do your job, this can be done with the \openout, \write and \closeout commands of TeX to output whatever you want to an auxilliary file, and then import it back by running \input on it. The file writing functions are described on pages 226--228 in the TeXBook.

-

You try this code.

\documentclass[12pt,openany,twoside]{book}
\usepackage{fouriernc}
\usepackage[thmmarks,standard,thref]{ntheorem}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsmath}

\theoremseparator{.}
\theorembodyfont{\upshape}
\newtheorem{pro}{Problem}[chapter]

\begin{document}
\chapter{Firist }
\thispagestyle{empty}
\Opensolutionfile{loigiaichung}[pro]
\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\Closesolutionfile{loigiaichung}
\section{This is solution}
\input{pro}

\chapter{Firist }
\thispagestyle{empty}
\Opensolutionfile{loigiaichung}[pro]
\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\Closesolutionfile{loigiaichung}
\section{This is solution}
\input{pro}

\end{document}

-
Why did you remove the code markup? Without it your post is quite unreadable! – clemens Oct 19 '12 at 16:36
I am sorry. I don't know. – minthao_2011 Oct 19 '12 at 23:07
Don't worry. I added it again. It's simple: just select the code part and then click the {} button. – clemens Oct 19 '12 at 23:10

This is another solution

\documentclass[12pt,openany,twoside]{book}
\usepackage{fouriernc}
\usepackage[thmmarks,standard,thref]{ntheorem}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsmath}

\theoremseparator{.}
\theorembodyfont{\upshape}
\newtheorem{pro}{Problem}[chapter]

\begin{document}
\chapter{Firist }
\thispagestyle{empty}
\Opensolutionfile{loigiaichung}[pro]
\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\chapter{Second }
\thispagestyle{empty}
\Opensolutionfile{loigiaichung}[pro]
\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\begin{pro}
This is a problem
\begin{loigiai}
This is a solution
\end{loigiai}
\end{pro}

\Closesolutionfile{loigiaichung}
\section{This is solution}
\input{pro}

\end{document}

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I don't see it. I what way is this different from your other one? – clemens Oct 19 '12 at 23:39
The answers are comment part. – minthao_2011 Oct 19 '12 at 23:41
The answers are commont part. – minthao_2011 Oct 19 '12 at 23:58