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+% \iffalse meta-comment
+%
+% Copyright (C) 2003 by Paul Pichaureau 
+%
+% This program is free software; you can redistribute it and/or
+% modify it under the terms of the GNU General Public License
+% as published by the Free Software Foundation; either version 2
+% of the License, or (at your option) any later version.
+%
+% This program is distributed in the hope that it will be useful,
+% but WITHOUT ANY WARRANTY; without even the implied warranty of
+% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+% GNU General Public License for more details.
+%
+% You should have received a copy of the GNU General Public License
+% along with this program; if not, write to the Free Software
+% Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+% Public LaTeX Project Public
+%
+% \fi
+
+
+% \iffalse
+%<package>\NeedsTeXFormat{LaTeX2e}[1999/12/01]
+%<package>\ProvidesPackage{exercise}
+%<package> [2004/09/05 v1.1 Exercise package (P.Pichaureau)]
+%<*driver>
+\documentclass{ltxdoc}
+\usepackage{exercise}
+\usepackage[latin1]{inputenc}
+\usepackage{xspace,fancyvrb}
+%% \IfFileExists{hyperref.sty}{\usepackage[bookmarksopen]{hyperref}}{}
+%% \def\PrintDescribeMacro#1{}
+%% \def\PrintDescribeEnv#1{}
+\newenvironment{decl}[1][]%
+    {\par\small\addvspace{4.5ex plus 1ex}%
+     \vskip -\parskip
+     \ifx\relax#1\relax
+        \def\@decl@date{}%
+     \else
+        \def\@decl@date{\NEWfeature{#1}}%
+     \fi
+     \noindent\hspace{-\leftmargini}%
+     \begin{tabular}{|l|}\hline\ignorespaces}%
+    {\\\hline\end{tabular}\nobreak\@decl@date\par\nobreak
+     \vspace{2.3ex}\vskip -\parskip}
+\makeatletter
+ \EnableCrossrefs \PageIndex \RecordChanges
+\makeatother
+\begin{document}
+  \DocInput{exercise.dtx}
+\end{document}
+%</driver>
+% \fi
+%% \CharacterTable
+%%  {Upper-case    \A\B\C\D\E\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z
+%%   Lower-case    \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z
+%%   Digits        \0\1\2\3\4\5\6\7\8\9
+%%   Exclamation   \!     Double quote  \"     Hash (number) \#
+%%   Dollar        \$     Percent       \%     Ampersand     \&
+%%   Acute accent  \'     Left paren    \(     Right paren   \)
+%%   Asterisk      \*     Plus          \+     Comma         \,
+%%   Minus         \-     Point         \.     Solidus       \/
+%%   Colon         \:     Semicolon     \;     Less than     \<
+%%   Equals        \=     Greater than  \>     Question mark \?
+%%   Commercial at \@     Left bracket  \[     Backslash     \\
+%%   Right bracket \]     Circumflex    \^     Underscore    \_
+%%   Grave accent  \`     Left brace    \{     Vertical bar  \|
+%%   Right brace   \}     Tilde         \~}
+%%
+% \DoNotIndex{\#,\$,\%,\&,\@,\\,\{,\},\^,\_,\~,\ }
+% \DoNotIndex{\@ne,\@auxout,\@ifnextchar,\@ifstar,\@ifundefined,\@bsphack,\@esphack,\@fleqnfalse}
+% \DoNotIndex{\advance,\begingroup,\begin,\bgroup,\catcode,\closein,\closeout}
+% \DoNotIndex{\day,\def,\edef,\else,\empty,\endgroup,\end,\egroup,\errmessage}
+% \DoNotIndex{\expandafter,\fi,\futurelet,\gdef,\global,\if,\ifeof}
+% \DoNotIndex{\ifx,\immediate,\let,\loop,\m@ne,\message,\month}
+% \DoNotIndex{\newcount}
+% \DoNotIndex{\newif,\newlinechar,\newread,\newtoks,\newwrite}
+% \DoNotIndex{\noexpand,\openin,\openout,\par,\quad,\read,\relax,\repeat}
+% \DoNotIndex{\space,\the,\undefined,\write,\xdef,\year,\z@}
+% \DoNotIndex{\item,\copy,\arabic,\addto,\addtolength,\alph}
+% \DoNotIndex{\ref,\Roman,\rmdefault,\or,\number,\medskip,\makebox}
+% \DoNotIndex{\fbox,\label,\ifcase,\ifnum,\ignorespaces,\newcommand}
+% \DoNotIndex{\renewenvironment,\renewcommand,\refstepcounter,\newenvironment}
+% \DoNotIndex{\setlength,\string,\textbf,\textsc,\emph,\whiledo,\vbox}
+% \DoNotIndex{\unvbox,\usefont,\usecounter,\value,\vskip,\setbox,\setcounter}
+%
+%\CheckSum{1426}
+%
+%
+% \GetFileInfo{exercise.sty}
+%
+% \makeatletter
+% \IndexPrologue{\section*{Index}%
+%                  \markboth{Index}{Index}%
+%                  For entries in type-writer font, numbers written in italic
+%                  refer to the page where the corresponding entry is
+%                  described; numbers underlined refer to the
+%                  \ifcodeline@index code line of the \fi definition;
+%                  numbers in roman refer to the \ifcodeline@index code
+%                  lines \else pages \fi where the entry is used.  }
+% \makeatother
+%\title{\texttt{exercise.sty} : a package to typeset exercises}
+%
+%\date{\today}
+%
+%\author{Paul Pichaureau\\ \texttt{paul.pichaureau@nerim.net}}
+%
+%\maketitle
+%
+%\begin{abstract}
+%    This package offers a simple environment to typeset exercises,
+%    and their questions, sub-questions, indications, answers and so
+%    on.
+%    
+%    The layout of the exercises is fully customisable. Moreover, the
+%    answers of the exercise could be typeset immediately or 
+%    later in the document.
+%\end{abstract}
+%
+%\changes{v1.0}{2004/08/17}{Initial version}
+%\changes{v1.01}{2004/08/18}{Many typos corrected, improved index.}
+%
+%\section{Simple usage}
+%
+%This package defines two environments. The environment |Exercise|
+%is used to typeset one exercise. For example, the following
+%output:\medskip\index{example}
+%
+%\noindent \fbox{\begin{minipage}[t]{.95\textwidth}
+%\begin{Exercise}[title={Duhamel's Rule}, label={ex:one}]
+%    \label{exe:ex1}
+%    Assume that the series $\sum x_n$ satisfies
+%    $$
+%        \frac{x_{n+1}}{x_n} = 1 - \frac{b}{n}+\frac{\varepsilon(n)}{n}
+%    $$
+%    where $b$ is a real number and the function $\varepsilon$ satisfies
+%    $$
+%        \lim_{n\rightarrow + \infty} \varepsilon(n) = 0.
+%    $$
+%    
+%    \Question Show that if $b < 1$, then the series $\sum x_n$ is
+%    divergent.
+%    
+%    \Question Show that if $b > 1$, then the series $\sum x_n$ is
+%    convergent.
+% 
+%    \Question What happens to $\sum x_n$ if $b=1$?
+%    
+%  \end{Exercise}
+%
+%\end{minipage}}
+%
+%\medskip \noindent is obtained by the following code (the text has been cut to underscore
+%the structure of the code):
+%\begin{verbatim}
+%\begin{Exercise}[title={Duhamel's Rule}]
+%   Assume...
+%   \Question Show that if $b < 1$...
+%   \Question Show that if $b > 1$...
+%   \Question What happens to if $b=1$?
+%\end{Exercise}
+%\end{verbatim}
+%
+%Up to three level of question are available, and a part level (between
+%exercise and question) is implemented:
+%\begin{verbatim}
+%\begin{Exercise}[title={Example}]
+%    Assume...
+%    \ExePart
+%    \Question 
+%      \subQuestion Show that... 
+%      \subQuestion In this question...
+%        \subsubQuestion Show that...
+%        \subsubQuestion Conclude...
+%      \subQuestion Conclude.
+%    \Question Show that if $b > 1$...
+%    \ExePart
+%    \Question What happens to if $b=1$?
+%\end{Exercise}
+%\end{verbatim}
+%
+%
+%The commands to typeset question, sub-question and sub-sub-question
+%are |Question|, |subQuestion|, and
+%|subsubQuestion|. The exercise is split in parts with the
+%command |ExePart|.
+%
+%The environment \texttt{Exercise} can be stared (no number is
+%typeset). The options of these commands are described in section
+%\ref{sec:option}. The layout of exercises can be customised in many
+%way: see section \ref{sec:custom}.
+%
+%It is common to have a long list of exercise to typeset, and the usage
+%of the |Exercise| environment could be cumbersome. Another
+%environment is available: the |ExerciseList| environment.
+%
+%\medskip
+%
+%\noindent \fbox{\begin{minipage}[t]{.95\textwidth}
+%\begin{ExerciseList}
+%    \Exercise[label={ex:two}] Discuss the convergence or divergence of $
+%    \left[1 + \sin \left(\frac1{an}\right)\right]^{bn}$
+%    where $a$ and $b$ are two parameters.
+%    
+%    \Exercise Discuss the convergence or divergence of $
+%    n^{\frac{(-1)^n}{n}} - 1$.
+%      
+%    \Exercise* Discuss the convergence or divergence of $
+%    \frac{(-1)^n}{n+(-1)^n}$.
+%    
+%    \Answer[ref={ex:two}] $ \displaystyle \lim_{n\rightarrow
+%        +\infty} \left[1 + \sin \left(\frac1{an}\right)\right]^{bn}= {\mathrm{e}}^{\frac{b}{a}}$
+%
+%\end{ExerciseList}
+%\end{minipage}}
+%
+%\medskip
+%
+%\begin{verbatim}
+%\begin{ExerciseList}
+%    \Exercise[label={ex:two}] Discuss...
+%    \Exercise Discuss...
+%    \Exercise* Discuss...
+%    \Answer[ref={ex:two}] $...$
+%\end{ExerciseList}
+%\end{verbatim}
+%
+%This example show two new commands: |\Exercise*| (for an exercise
+%without number) and |\Answer|. These commands are explained in detail
+%later in this document.
+%
+%Of course, the |\Question|, |\subQuestion|, and |\subsubQuestion|
+%hierarchy is also available in |ExerciseList|:
+%
+%\begin{verbatim}
+%\begin{ExerciseList}
+%    \Exercise Discuss...
+%    \Exercise Let $u$...
+%      \Question ...
+%        \subQuestion ...
+%      \Question
+%    \Exercise What...
+%\end{ExerciseList}
+%\end{verbatim}
+%
+%\section{Options of the package}
+%
+%\index{package>options}\index{options>of the package}
+%
+%Here we list the options of the package |exercise.sty|:
+%
+%\begin{description}
+%        \item[|noexercise|] hide all the exercises
+%    of a document.
+%    
+%        \item[|noanswer|] hide all the answers
+%    of a document. The default behaviour is to show both the exercises
+%    and the answers.
+%        
+%
+%        \item[|exerciseonly|] is a synonym of |noanswer|.
+%    
+%        \item[|answeronly|] is a synonym of |noexercise|.
+%    
+%        \item[|nothing|] hide answers and exercises (synonym of
+%    |noanswer| and |noexercise|).
+%    
+%        \item[|answerdelayed|] save the answers instead of typeset
+%    them. The answers can be included later in the document with the
+%    command |\shipoutAnswer|. More precisely, the answers are stored
+%    in a vertical box. When |\shipoutAnswer| is encountered, this box
+%    is emptied and its contents is placed in the main vertical
+%    list. The answers defined later are placed in this emptied
+%    vertical box. In this way, you can have many group of answers in
+%    the same document.
+%    
+%        \item[|exercisedelayed|] saves the exercises instead of
+%    typeset them. The exercises can be included later with the command
+%    |\shipoutExercise|.
+%
+%        \item [|lastexercise|] if no references is given for an
+%    answer, then the answer is supposed to refer to the last
+%    exercise (see section \ref{sec:lastexercise}).
+%
+%\end{description}
+%
+%
+%\section{Commands}
+%
+%\label{sec:option}
+%
+%\subsection{Exercises and answers}
+%
+% 
+%\begin{decl}
+%    |\begin{Exercise}| \oarg{key val list} ... |\end{Exercise}| \\
+%    |\begin{Exercise*}| \oarg{key val list} ... |\end{Exercise*}|
+%\end{decl}
+%
+%\DescribeEnv{Exercise}\DescribeEnv{Exercise*}
+%The |Exercise| environment is used to typeset just one exercise. We
+%use the \textsf{keyval} package to give different informations about
+%an exercise.
+%
+%\vspace*{-\baselineskip}
+%
+%\index{options>of \texttt{Exercise}}
+%\index{keys>of \texttt{Exercise}}
+%\begin{decl}
+%|label|=\marg{string}\\
+%|title|=\marg{string}\\
+%|difficulty|=\marg{number}\\
+%|origin|=\marg{string}\\
+%|name|=\marg{string}\\
+%|counter|=\marg{counter}\\
+%|number|=\marg{string}
+%\end{decl}
+%All these keys define commands that will be available later to typeset
+%the exercise. They are all optional. 
+%\begin{description}
+%         \item[|label|] The label of the exercise. This label can be
+%    used later in cross-reference, or to link an answer to this
+%    exercise. 
+%        \item[|title|] The title of the exercise. It will be available
+%    later with the command |\ExerciseTitle|.
+%        \item[|difficulty|] The difficulty of the exercise (a number).
+%    It will be available later with the counter
+%    |\ExerciseDifficulty|.
+%        \item[|origin|] The origin of the exercise.
+%    It will be available later with the command |\ExerciseOrigin|.
+%        \item[|name|] In document, exercises can have multiple
+%    denomination, like problem, exam, or even question. This key
+%    allows to change the denomination.
+%        \item[|counter|] Use the given counter to number this 
+%    exercise. Here, \marg{counter} must be a pre-defined counter.
+%        \item[|number|] Use the given number for the exercise. In
+%    fact, this number is a string, so you can number the exercise
+%    with letters.
+%\end{description}
+%
+%As an example, with the default definitions, the following code:
+%\medskip
+%\begin{verbatim}
+%\begin{Exercise}[title={Euler's constant}, difficulty=2, 
+%                 origin={P.Paelw}]
+%\end{Exercise}
+%\end{verbatim}
+%\noindent will give \par \medskip
+%\index{example}
+%\noindent \fbox{\begin{minipage}[t]{.95\textwidth}
+%\begin{Exercise}[title={Euler's constant}, difficulty=2, 
+%                 origin={P.Paelw}]
+%\end{Exercise}
+%\end{minipage}}
+%
+%\DescribeEnv{Problem}
+%It is possible to define different type of exercise. For example,
+%you can define a |Problem| environment with the two lines:
+%\begin{verbatim}
+%    \newcounter{Problem}
+%    \newenvironment{Problem}{\begin{Exercise}[name={Problem}, 
+%                                              counter={Problem}]}
+%                            {\end{Exercise}}
+%\end{verbatim}
+%Anyway, all type of exercise will have the same layout in the document.
+%
+%\begin{decl}
+%    |\begin{Answer}| \oarg{key val list} ... |\end{Answer}| 
+%\end{decl}
+%
+%\DescribeEnv{Answer}
+%The |Answer| environment is used to typeset the answer of an
+%exercise. To determine which the exercise this answer is attributed
+%to, you can use the two following keys.
+%
+%\vspace*{-\baselineskip}
+%\index{options>of \texttt{Answer}}
+%\index{keys>of \texttt{Answer}}
+%\begin{decl}
+%|ref|=\marg{string}\\
+%|number|=\marg{string}
+%\end{decl}
+%This is the description of these keys:
+%\begin{description}
+%        \item[|ref|] a \LaTeX\ reference. \emph{Must} correspond to the |label|
+%    key of an exercise.
+%        \item[|number|] if the answer refers to an exercise in
+%    another document, you can set the number of the exercise with this
+%    key. It is in fact a string.
+%\end{description}
+%
+%\label{sec:lastexercise} If the package is loaded with the option
+% |lastexercise| and if no |ref| and no |number| key is given, then
+% the last exercise is taken as a reference for the answer.
+%
+%If no |ref| and no |number| key is given and the option |lastexercise|
+%is not activated, a Package Warning is displayed.
+%
+%\begin{decl}
+%    |\begin{ExerciseList}| \\
+%        \quad |\Exercise|\oarg{key val list} \\
+%        \quad |\Answer|\oarg{key val list} \\
+%    |\end{Exercise}| 
+%\end{decl}
+%
+%\DescribeEnv{ExerciseList}
+%The |ExerciseList| environment is a convenience to typeset a list of
+%small exercises. In |ExerciseList|, everything between two |\Exercise|
+%or |\Answer| tags is interpreted as the body of an exercise (or an
+%answer).
+%
+%\DescribeMacro{\Exercise}
+%\DescribeMacro{\Exercise*}
+%\DescribeMacro{\Answer}
+%The command |\Exercise| inside |ExerciseList| accepts the same keys
+%than the |Exercise| environment. The command |\Answer| inside
+%|ExerciseList| accepts the same keys than the |Answer| environment and
+%behaves in the same way.
+%
+%\subsection{Parts and questions}
+%
+%\begin{decl}
+%    |\ExePart|\oarg{key val list} \\
+%    |\ExePart*|\oarg{key val list}
+%\end{decl}
+%\DescribeMacro{\ExePart}
+%\DescribeMacro{\ExePart*}
+%It is common to split large exercise in parts: it is the purpose of
+%the |\ExePart| command. 
+%\index{options>of \texttt{\bslash ExePart}}
+%\index{keys>of \texttt{\bslash ExePart}}
+%The keys |title|, |name| and |difficulty| are
+%available for this command.
+%
+%For example, a non-numbered preliminary part is obtained with
+%\begin{verbatim}
+%    \ExePart*[name={Preliminary}]
+%\end{verbatim}
+%
+%\begin{decl}
+%    |\Question|\oarg{key val list}\\
+%    |\subQuestion|\oarg{key val list}\\
+%    |\subsubQuestion|\oarg{key val list}
+%\end{decl}
+%\DescribeMacro{\Question}
+%\DescribeMacro{\subQuestion}
+%\DescribeMacro{\subsubQuestion}
+%These three commands define the hierarchy of questions. A
+%|\subsubQuestion| cannot be preceded by a |\Question| or a
+%|\begin{Exercise}|. A |\subQuestion| cannot be preceded by a
+%    |\begin{Exercise}|. If one of these cases is detected, a Package
+%        Error is displayed.
+%
+%\index{options>of \texttt{\bslash Question}}
+%\index{keys>of \texttt{\bslash Question}}
+%\index{options>of \texttt{\bslash subQuestion}}
+%\index{keys>of \texttt{\bslash subQuestion}}
+%\index{options>of \texttt{\bslash subsubQuestion}}
+%\index{keys>of \texttt{\bslash subsubQuestion}}
+%Two keys are available for these commands: |title| and |difficulty|.
+%
+%\begin{decl}
+%    |\ExeText|
+%\end{decl}
+%\DescribeMacro{\ExeText}
+%The text following this command has the same status that the first
+%indications of the exercise. So, the next level of the hierarchy must
+%be a |\ExePart| or a |\Question|.
+%
+%
+%\subsection{Extra stuff}
+%\DescribeMacro{\marker}
+%\DescribeMacro{\DifficultyMarker}
+%The difficulty of an exercise is represented by a certain amount of
+%stars. The command |\marker| is used to typeset the difficulty of an
+%exercise. 
+%\begin{verbatim}
+%    \marker<symbol><counter>
+%\end{verbatim}
+%displays |<symbol>| repeated |<counter>| times.  For example |\marker*2|
+% gives **, and |\marker+{14}| gives ++++++++++++++
+%
+% By default, the difficulty is symbolized by star. You can customise
+% this by redefining the command |\DifficultyMarker|.
+%
+%\section{Customisation}
+%
+%\label{sec:custom}
+%
+%\subsection{Internationalisation}
+%
+%\begin{decl}
+%|\ExerciseName|\\
+%|\ExerciseListName|\\
+%|\AnswerName|\\
+%|\AnswerListName|\\
+%|\ExePartName|% 
+%\end{decl}
+%\DescribeMacro{\ExerciseName}
+%\DescribeMacro{\ExerciseListName}
+%\DescribeMacro{\AnswerName}
+%\DescribeMacro{\AnswerListName}
+%\DescribeMacro{\ExePartName}
+%\DescribeMacro{\ExePartListName}
+%These commands store various hard-wired string. |\ExerciseListName|
+%is used in the |ExerciseList| environment: it is possibly an
+%abbreviation of the word ``Exercise".
+%
+%\textsf{Exercise.sty} automatically detects the usage of
+% \textsf{babel} and translate these terms in the language loaded...
+% if I (the author) know the translation! As my skills in foreign
+% language are quite weak, only English and French are currently
+% supported.
+%
+%If you sent me the translations in your language, I will be happy to
+%add them in the package. Anyway, you can redefine these
+%commands (with a |\renewcommand|).
+%
+%\subsection{Layout}
+%
+%\subsubsection{Exercises, answers and parts}
+%
+%For the layout of the exercises, two levels of customisation are
+%available. First, you can customise the way the informations will be
+%typeset, and then you can customise the way these pieces of
+%informations are typeset together.
+%
+%\begin{decl}
+%    |\ExerciseHeaderTitle| \\
+%    |\ExerciseHeaderDifficulty| \\
+%    |\ExerciseHeaderOrigin|\\
+%    |\ExerciseHeaderNB|
+%\end{decl}
+%\DescribeMacro{\ExerciseHeaderTitle}
+%\DescribeMacro{\ExerciseHeaderDifficulty}
+%\DescribeMacro{\ExerciseHeaderOrigin}
+%\DescribeMacro{\ExerciseHeaderNB}
+%These commands are used to typeset the corresponding information:
+%\\ |\ExerciseHeaderTitle| corresponds to the |title| key, \\
+%|\ExerciseHeaderDifficulty| to the |difficulty| key,
+%|\ExerciseHeaderOrigin| to the |origin| key and |\ExerciseHeaderNB| to
+%the number of the exercise.
+%
+%In these commands, you specify the fonts to use, the space around the
+%information, some symbols (like dash or dot) you want to put here, and
+%so on. If the key is not present in the definition of the exercise,
+%then the corresponding part of the header will be emptied by the package.
+%
+%For example the default definition of |\ExerciseHeaderTitle| is
+%\begin{verbatim}
+%    \newcommand{\ExerciseHeaderTitle}{\quad---\quad\ExerciseTitle}
+%\end{verbatim}
+%If an exercise has a title, then this title will be displayed preceded
+%by an emdash (as you can see in exercise \ref{exe:ex1} of this
+%document). If an exercise doesn't have a title, then this command is
+%set to nothing (precisely to |{}|) during the exercise.
+%
+%These commands can be redefined with a |\renewcommand|. You don't have
+%to worry about the ``undefinition" mechanism: the package manages that
+%by itself.
+%
+%\begin{decl}
+%    |\ExerciseHeader| \\
+%    |\ExerciseListHeader|
+%\end{decl}
+%\DescribeMacro{\ExerciseHeader}
+%\DescribeMacro{\ExerciseListHeader}
+%When the layout of all the elements has been fixed, they are collected
+%in the |\ExerciseHeader| command (or in |\ExerciseListHeader|).
+%Here, you specify the way the different elements are mixed
+%together.
+%
+%The default definition of |\ExerciseHeader| is
+%\begin{verbatim}
+%    \newcommand{\ExerciseHeader}{\centerline{\textbf{\large
+%                \ExerciseName\ExerciseHeaderNB\ExerciseHeaderTitle
+%                \ExerciseHeaderOrigin\medskip}}}
+%\end{verbatim}
+%\noindent which displays all the informations in a centered line, using
+%a large bold default font.
+%                
+%\begin{decl}
+%    |\AnswerHeader| \\
+%    |\AnswerListHeader|
+%\end{decl}
+%\DescribeMacro{\AnswerHeader}
+%\DescribeMacro{\AnswerListHeader}
+%The same mechanism is implemented for the answers. 
+%|\AnswerHeader| and |\AnswerListHeader| specifies the way the header
+%of answers are typeset. In the definition of these commands, you can
+%use freely the informations of the related exercise. For example, this
+%is the default definition of |\AnswerHeader|:
+%
+%\begin{verbatim}
+%    \newcommand{\AnswerHeader}{\medskip\centerline{\textbf{
+%                Answer of \ExerciseName\ \ExerciseHeaderNB}\smallskip}}
+%\end{verbatim}
+%
+%
+%\begin{decl}
+%    |\ExePartHeaderTitle| \\
+%    |\ExePartHeaderDifficulty| \\
+%    |\ExePartHeaderNB|\\
+%    |\ExePartHeader|\\
+%    |\ExePartListHeader|
+%\end{decl}
+%\DescribeMacro{\ExePartHeaderTitle}
+%\DescribeMacro{\ExePartHeaderDifficulty}
+%\DescribeMacro{\ExePartHeaderNB}
+%\DescribeMacro{\ExePartHeader}
+%\DescribeMacro{\ExePartListHeader}
+%The same kind of customisation is available for the |\ExePart|
+%command: |\ExePartHeaderTitle|, |\ExePartHeaderDifficulty| and
+%|\ExePartHeaderNB| \\ control the way the title (|\ExePartTitle|), the
+%difficulty (|\ExePartdifficulty|) and  the number (|\theExePart|) of
+%the part are displayed.
+%
+%These pieces are collected in the command |\ExePartHeader| or 
+%\\ |\ExePartListHeader|.
+%
+%
+%
+%\subsubsection{Questions, sub-questions and sub-sub-questions}
+%
+%The layout of the questions is a little more rigid. Somehow, it can be
+%customised.
+%
+%\begin{decl}
+%    |\QuestionHeaderTitle| \\
+%    |\QuestionHeaderDifficulty| \\
+%    |\QuestionHeaderNB|
+%\end{decl}
+%
+%\DescribeMacro{\QuestionHeaderTitle}
+%\DescribeMacro{\QuestionHeaderDifficulty}
+%\DescribeMacro{\QuestionHeaderNB}
+%\DescribeMacro{\subQuestionHeaderTitle}
+%\DescribeMacro{\subQuestionHeaderDifficulty}
+%\DescribeMacro{\subQuestionHeaderNB}
+%\DescribeMacro{\subsubQuestionHeaderTitle}
+%\DescribeMacro{\subsubQuestionHeaderDifficulty}
+%\DescribeMacro{\subsubQuestionHeaderNB}
+%These commands plays the same role that the corresponding command
+%relating to exercises. But here, no |\QuestionHeader| is defined.
+%
+%The |subQuestion| and |subsubQuestion| versions of these commands are
+%also defined.
+%
+%All of these commands can be changed using |\renewcommand|.
+%
+%
+%\subsection{Lengths}
+%
+%\begin{decl}
+%    \begin{tabular}{llll}
+%    |\Exesep| & |\Exetopsep| & |\Exeparsep| &
+%    |\Exepartopsep| \\
+%    |\Exeleftmargin| & |\Exerightmargin| & |\Exelabelwidth|
+%    & |\Exelabelsep|
+%\end{tabular}
+%\end{decl}
+%\DescribeMacro{Exesep} 
+%\DescribeMacro{Exetopsep} 
+%\DescribeMacro{Exeparsep} 
+%\DescribeMacro{Exepartopsep} 
+%\DescribeMacro{Exeleftmargin} 
+%\DescribeMacro{Exerightmargin} 
+%\DescribeMacro{Exelabelsep}
+%The |ExerciseList| environment is nothing more than a |list|
+%environment. All the parameters of \LaTeX's lists are
+%available. Please consult your favourite source of information to have
+%the exact definitions of these lengths.
+%
+%\begin{decl}
+%    \begin{tabular}{ll}
+%        |\QuestionBefore| & |\QuestionIndent| \\
+%        |\subQuestionBefore| & |\subQuestionIndent| \\
+%        |\subsubQuestionBefore| & |\subsubQuestionIndent| \\
+%    \end{tabular}
+%\end{decl}
+%\DescribeMacro{QuestionBefore}
+%\DescribeMacro{QuestionIndent}
+%\DescribeMacro{subQuestionBefore}
+%\DescribeMacro{subQuestionIndent}
+%\DescribeMacro{subsubQuestionBefore}
+%\DescribeMacro{subsubQuestionIndent}
+%Here, |\QuestionBefore| is the vertical space above |\Question|, and\\
+%|\QuestionIndent| it the horizontal distance added to the margin in
+%question. Same thing for |\subQuestion| and |\subsubQuestion|.
+%
+% \subsection{The \texttt{\textbackslash renewcounter} command}
+%
+%\changes{v1.1}{2004/09/05}{Added the 'renewcounter' command.}
+%
+% In a document, you will probably want to customise the way the
+% |Exercise| counter will reseted. Strangely, it is impossible to
+% redefined counter with \LaTeX. There is no equivalent of the
+% |\renewcommand| command for the counters.
+%
+% We provide such an equivalent with the command |\renewcounter|.
+%\DescribeMacro{\renewcounter}
+%
+%\begin{decl}
+%    |\newcounter|\marg{foo}\oarg{counter}
+%\end{decl}
+%    The |\renewcounter| command defines a new counter named |foo|.  The
+% counter is initialized to zero.
+%
+%    The optional argument \oarg{counter} causes the counter |foo| to be
+% reset whenever the counter named in the optional argument is
+% incremented.
+%
+% If the counter |foo| was not previously defined, an \LaTeX\ error
+% occurs.
+%
+%\section{Known problems}
+%
+%The commands |\Question|, |\subQuestion|, etc. are heavily based
+%on |list| environment. These lists are hidden (I know it's bad!) to
+%simplify the syntax of the source file (I think it's nice!).
+%
+%In fact, every |\Question| is like the beginning of an environment,
+%which is closed at the next |\Question| (the exact mechanism is a
+%little bit more complicated).
+%
+%Consequently it's dangerous to put questions inside environment. 
+%The following code will lead to an error:
+%\vspace*{-.5\baselineskip}
+%\begin{verbatim}
+%    \begin{Exercise}
+%        \begin{multicols}{2}
+%            \Question ... 
+%            \Question ...
+%        \end{multicols}
+%    \end{Exercise}
+%\end{verbatim}
+%Of course, you can put entire exercise inside other environment (like
+%|minipage|). The following code will work:
+%\vspace*{-.5\baselineskip}
+%\begin{verbatim}
+%    \begin{multicols}{2}
+%        \begin{Exercise}
+%            \Question ...
+%            \Question ...
+%        \end{Exercise}
+%    \end{multicols}
+%\end{verbatim}
+%
+%\begin{decl}
+%    |\EndCurrentQuestion| \\
+%    |\EndCurrentsubQuestion| \\
+%    |\EndCurrentsubsubQuestion|
+%\end{decl}
+%\DescribeMacro{\EndCurrentQuestion}
+%\DescribeMacro{\EndCurrentsubQuestion}
+%\DescribeMacro{\EndCurrentsubsubQuestion}
+%If you really need to put some questions inside environment, you must
+%use the command |\EndCurrentQuestion| just before ending the
+%environment. This command ends the question's ``environment". So,
+%this code will work:
+%\vspace*{-.5\baselineskip}
+%\begin{verbatim}
+%    \begin{Exercise}
+%        \begin{multicols}{2}
+%            \Question ... 
+%            \Question ...
+%            \EndCurrentQuestion
+%        \end{multicols}
+%    \end{Exercise}
+%\end{verbatim}
+%
+%
+%
+%
+%
+%In |ExerciseList| environment, the command |\Exercise| shouldn't be
+%followed by an empty line.
+%
+% \PrintChanges
+%
+%\makeatletter\c@IndexColumns = 2\makeatother
+% \StopEventually{\PrintIndex\newpage\tableofcontents }
+%
+% \section{Implementation}
+%
+% \subsection{Package options}
+% This part deals with the package options. Nothing more than an
+% affair of boolean.
+%    \begin{macrocode}
+\newif\if@AnswerOutput        \@AnswerOutputtrue
+\newif\if@AnswerDelay         \@AnswerDelayfalse
+\newif\if@ExerciseOutput      \@ExerciseOutputtrue
+\newif\if@ExerciseDelay       \@ExerciseDelayfalse
+\newif\if@AswLastExe          \@AswLastExefalse
+
+\DeclareOption{noanswer}     {\@AnswerOutputfalse}
+\DeclareOption{answeronly}   {\@ExerciseOutputfalse}
+\DeclareOption{noexercise}   {\@ExerciseOutputfalse}
+\DeclareOption{exerciseonly} {\@AnswerOutputfalse}
+\DeclareOption{outputnothing}{\@ExerciseOutputfalse\@AnswerOutputfalse}
+\DeclareOption{exercisedelayed}{\@ExerciseDelaytrue}
+\DeclareOption{answerdelayed}{\@AnswerDelaytrue}
+\DeclareOption{lastexercise} {\@AswLastExetrue}
+%    \end{macrocode}
+% The following option, which displays the exercise label in margin, is
+% not implemented yet.
+%     \begin{macrocode}
+\newif\if@ShowLabel              \@ShowLabelfalse
+\DeclareOption{showlabel}       {\@ShowLabeltrue}
+
+\ProcessOptions
+%    \end{macrocode}
+% The only required package are \textsf{keyval} and \textsf{ifthen}.
+%    \begin{macrocode}
+\RequirePackage{keyval, ifthen}
+%    \end{macrocode}
+% 
+%\subsection{Customisation}
+% 
+%\subsubsection{Internationalisation}
+%    \begin{macrocode}
+\def\ExerciseName{Exercise}%
+\def\AnswerName{Answer}%
+\def\ExerciseListName{Ex.}%
+\def\AnswerListName{Answer}%
+\def\ExePartName{Part}% 
+\@ifpackageloaded{babel}{
+\addto{\captionsfrenchb}{
+  \def\ExerciseName{Exercise}%
+  \def\AnswerName{Solution}%
+  \def\ExerciseListName{Ex.}%
+  \def\AnswerListName{Sol.}%
+  \def\ExePartName{Partie}% 
+}}
+%    \end{macrocode}
+%\subsubsection{Layout}
+% First a bunch of length definitions.
+%    \begin{macrocode}
+\newlength{\Exesep}
+\setlength{\Exesep}{1\baselineskip}
+\newlength{\Exetopsep}
+\setlength{\Exetopsep}\z@
+\newlength{\Exeparsep}
+\setlength{\Exeparsep}\z@
+\newlength{\Exepartopsep}
+\setlength{\Exepartopsep}\z@
+\newlength{\Exeleftmargin}
+\setlength{\Exeleftmargin}\z@
+\newlength{\Exerightmargin}
+\setlength{\Exerightmargin}\z@
+\newlength{\Exelabelwidth}
+\setlength{\Exelabelwidth}\z@
+\newlength{\Exelabelsep}
+\setlength{\Exelabelsep}\z@
+\newlength{\ExerciseBefore}
+\setlength{\ExerciseBefore}{0em}
+\newlength{\QuestionBefore}
+\setlength{\QuestionBefore}{.25em}
+\newlength{\subQuestionBefore}
+\setlength{\subQuestionBefore}{0em}
+\newlength{\subsubQuestionBefore}
+\setlength{\subsubQuestionBefore}{0em}
+\newlength{\QuestionIndent}
+\setlength{\QuestionIndent}{3em}
+\newlength{\subQuestionIndent}
+\setlength{\subQuestionIndent}{2em}
+\newlength{\subsubQuestionIndent}
+\setlength{\subsubQuestionIndent}{1.5em}
+%    \end{macrocode}
+% Now the counters
+%    \begin{macrocode}
+\newcounter{Exercise}
+\gdef\@ExerciseCounter{Exercise}          %default exercise counter
+\newcounter{ExePart}[Exercise]
+\newcounter{Question}[Exercise]
+\newcounter{subQuestion}[Question]
+\newcounter{subsubQuestion}[subQuestion]
+%    \end{macrocode}
+% Presentation of these labels in cross references
+%    \begin{macrocode}
+\renewcommand{\theExercise}{\arabic{\@ExerciseCounter}}
+\renewcommand{\theExePart}{\Roman{ExePart}}
+\renewcommand{\theQuestion}{\arabic{Question}}
+\renewcommand{\thesubQuestion}{\alph{subQuestion}}
+\renewcommand{\thesubsubQuestion}{\arabic{subsubQuestion}}
+%    \end{macrocode}
+% For internal purposes
+%    \begin{macrocode}
+\newcounter{savedQuestion} 
+\newcounter{savedsubQuestion} 
+\newcounter{savedsubsubQuestion} 
+%    \end{macrocode}
+% The |\marker| command.
+%    \begin{macrocode}
+    \def\marker#1#2{\@tempcnta#2\whiledo{\@tempcnta>0}{#1\advance
+            \@tempcnta by -1 }}
+%    \end{macrocode}
+% Symbol used to indicate the difficulty of an exercise or a question
+%    \begin{macrocode}
+\def\DifficultyMarker{*}
+%    \end{macrocode}
+% Presentation of informations in the header of exercises
+%    \begin{macrocode}
+\newcommand{\ExerciseHeaderTitle}{\quad --- \quad \ExerciseTitle}
+\newcommand{\ExerciseHeaderDifficulty}{\theExerciseDifficulty\ }
+\newcommand{\ExerciseHeaderOrigin}{%
+\ ({\usefont{\encodingdefault}{\rmdefault}{m}{it}\ExerciseOrigin})}
+\newcommand{\ExerciseHeaderNB}{\ \theExercise}
+\newcommand{\ExerciseHeaderLabel}{\fbox{\textsc{\ExerciseLabel}}}
+%    \end{macrocode}
+% The header itself
+%    \begin{macrocode}
+\newcommand{\ExerciseHeader}{\centerline{%
+\textbf{\large\ExerciseHeaderDifficulty\ExerciseName%
+\ExerciseHeaderNB\ExerciseHeaderTitle\ExerciseHeaderOrigin}}\medskip}
+%    \end{macrocode}
+% The header of exercise in ExerciseList environment
+%    \begin{macrocode}
+\newcommand{\ExerciseListHeader}{\ExerciseHeaderDifficulty%
+\textbf{\ExerciseListName\ExerciseHeaderNB%
+\ --- \ \ExerciseHeaderTitle}%
+\ExerciseHeaderOrigin\ignorespaces}
+%    \end{macrocode}
+% Presentation of informations in the header of ExePart
+%    \begin{macrocode}
+\newcommand{\ExePartHeaderNB}{\ \theExePart}
+\newcommand{\ExePartHeaderTitle}{\quad --- \quad {\ExePartTitle}}
+\newcommand{\ExePartHeaderDifficulty}{\theExePartDifficulty\ }
+%    \end{macrocode}
+% The header of |ExePart|
+%    \begin{macrocode}
+\newcommand{\ExePartHeader}{%
+\medskip\centerline{\emph{\large\ExePartHeaderDifficulty\ExePartName%
+\ExePartHeaderNB\ExePartHeaderTitle}}}
+%    \end{macrocode}
+% Presentation of Questions
+%    \begin{macrocode}
+\newcommand{\QuestionNB}{\arabic{Question}.\ }
+\newcommand{\QuestionHeaderTitle}{\emph{(\QuestionTitle)}\ }
+\newcommand{\QuestionHeaderDifficulty}{\theQuestionDifficulty\ }
+\newcommand{\theQuestionDifficulty}{\marker{\DifficultyMarker}%
+{\QuestionDifficulty}}
+\newcommand{\subQuestionNB}{\alph{subQuestion})}
+\newcommand{\subQuestionHeaderTitle}{\emph{(\subQuestionTitle)}\ }
+\newcommand{\subQuestionHeaderDifficulty}{\thesubQuestionDifficulty\ }
+\newcommand{\subQuestionHeader}{\subQuestionHeaderDifficulty%
+    \subQuestionNB)\ \emph{\subQuestionHeaderTitle}}
+\newcommand{\thesubQuestionDifficulty}{\marker{\DifficultyMarker}%
+{\subQuestionDifficulty}}
+\newcommand{\subsubQuestionNB}{\arabic{subsubQuestion} -- }
+\newcommand{\subsubQuestionHeaderTitle}{\emph{(\subsubQuestionTitle)}\ }
+\newcommand{\subsubQuestionHeaderDifficulty}{\thesubsubQuestionDifficulty\ }
+\newcommand{\subsubQuestionHeader}{\subsubQuestionHeaderDifficulty%
+    \subsubQuestionNB \emph{\subsubQuestionHeaderTitle} --}
+\newcommand{\thesubsubQuestionDifficulty}{%
+\marker{\DifficultyMarker}{\subsubQuestionDifficulty}}
+%    \end{macrocode}
+% \subsection{Macros definition}
+%    \begin{macrocode}
+\newcount\@QuestionLevel \@QuestionLevel=0
+\newcommand{\the@QuestionLevel}{\number\@QuestionLevel}
+\newbox\@Exercisebox
+\newbox\all@Exercisebox
+\newbox\temp@Exercisebox
+\newbox\all@Answerbox
+\newbox\temp@Answerbox
+\newif\if@echapq \@echapqfalse
+\newif\if@Answer                \@Answerfalse
+\def\termineliste#1{\global\@echapqfalse%
+\whiledo{\@QuestionLevel>#1}%
+{\ifnum\@QuestionLevel=\colonnesLevel\end{multicols}\colonnesLevel=-10\fi%
+\end{list}\advance\@QuestionLevel by -1}%
+\ifnum\@QuestionLevel=\colonnesLevel\end{multicols}\colonnesLevel=-10\fi}
+%    \end{macrocode}
+%
+% \subsubsection{Definition of \texttt{Exercise}}
+%
+% The keyval package is used to specify various information about an exercise.
+%    \begin{macrocode}
+\newif\if@ExeTitle                        \@ExeTitlefalse
+\newif\if@ExeReName                       \@ExeReNamefalse
+\global\newcount\ExerciseDifficulty       \ExerciseDifficulty=0
+\newif\if@ExeDifficulty                   \@ExeDifficultyfalse
+\newif\if@ExeOrigin                       \@ExeOriginfalse
+\newif\if@ExeLabel                        \@ExeLabelfalse
+\newif\if@ExeNB                           \@ExeNBfalse
+%
+\def\theExerciseDifficulty{\marker{\DifficultyMarker}{\ExerciseDifficulty}}
+%
+\define@key{PPExercise}{title}%
+{\global\@ExeTitletrue\gdef\ExerciseTitle{\string#1}}
+\define@key{PPExercise}{difficulty}%
+{\global\@ExeDifficultytrue\global\ExerciseDifficulty=\number#1}
+\define@key{PPExercise}{name}%
+{\global\@ExeReNametrue\gdef\@ExerciseName{\string#1}}
+\define@key{PPExercise}{origin}%
+{\global\@ExeOrigintrue\gdef\ExerciseOrigin{#1}}
+\define@key{PPExercise}{counter}%
+{\gdef\@ExerciseCounter{\string#1}}
+\define@key{PPExercise}{label}%
+{\global\@ExeLabeltrue\gdef\ExerciseLabel{\string#1}}
+\define@key{PPExercise}{number}%
+{\global\@ExeNBtrue\gdef\ExerciseLocalNB{\string#1}}
+%
+%% \define@key{PPExercise}{domain}{}
+%% \define@key{PPExercise}{sdomain}{}
+%% \define@key{PPExercise}{keyword}{}
+%
+\newif\if@ExeStared
+\newif\if@staredpb
+\newif\if@staredpart
+\newif\if@renamepart
+%
+\@ExeStaredfalse
+\@staredpbfalse
+\@staredpartfalse
+\@renamepartfalse
+%
+\def\@InitExe{\@savemathindent\global\@echapqfalse%
+\gdef\ExerciseTitle{}%
+\gdef\@ExerciseName{}%
+\gdef\ExerciseOrigin{}%
+\gdef\labelexe{}%
+\global\ExerciseDifficulty=0%
+\global\@ExeTitlefalse%
+\global\@ExeReNamefalse%
+\global\@ExeDifficultyfalse%
+\global\@ExeOriginfalse%
+\global\@ExeNBfalse%
+\gdef\@ExerciseCounter{Exercise}%
+\setcounter{Question}{0}%
+\global\@ExeLabelfalse}
+%
+\def\@getExerciseInfo{%
+\if@ExeReName\def\ExerciseName{\@ExerciseName}\fi%
+\if@ExeTitle\else\def\ExerciseHeaderTitle{}\fi%
+\if@ExeOrigin\else\def\ExerciseHeaderOrigin{}\fi%
+\if@ExeLabel\else\def\ExerciseHeaderLabel{}\fi%
+\if@ExeDifficulty\else\def\ExerciseHeaderDifficulty{}\fi%
+\if@ExeStared\def\ExerciseHeaderNB{}\fi%
+\if@ExeNB\def\theExercise{\ExerciseLocalNB}\fi%
+\if@ExeLabel\label{\ExerciseLabel}\recordExerciseLabel{\ExerciseLabel}\fi%
+}
+%
+\def\refstepExecounter{\if@ExeStared\else\if@ExeNB\else%
+\refstepcounter{\@ExerciseCounter}\fi\fi}
+%
+\def\recordExerciseLabel#1{\@bsphack
+  \protected@write\@auxout{}%
+         {\string\newlabel{PP#1}{{\@AnswerHeaderRef}{\thepage}}}%
+  \@esphack}
+%
+\def\@BeginExeBox{\global\setbox\@Exercisebox\vbox\bgroup}
+\def\@EndExeBox{\egroup\if@Answer\if@AnswerOutput\@DelayAnswerBox\fi%
+\else\if@ExerciseOutput\@DelayExerciseBox\fi\fi}
+%
+\def\@DelayAnswerBox{%
+\if@AnswerDelay\global\setbox\temp@Answerbox%
+\vbox{\unvbox\all@Answerbox\vskip12pt\unvbox\@Exercisebox\vskip\z@}%
+\global\setbox\all@Answerbox\copy\temp@Answerbox%
+\else\unvbox\@Exercisebox\fi}
+%
+\def\@DelayExerciseBox{\if@ExerciseDelay%
+\global\setbox\temp@Exercisebox%
+\vbox{\unvbox\all@Exercisebox\vskip12pt\unvbox\@Exercisebox\vskip\z@}%
+\global\setbox\all@Exercisebox\copy\temp@Exercisebox%
+\else\unvbox\@Exercisebox\fi}
+%
+\newcommand{\shipoutAnswer}{\if@AnswerOutput\unvbox\all@Answerbox\fi}
+\newcommand{\shipoutExercise}{\if@ExerciseOutput\unvbox\all@Exercisebox\fi}
+%    \end{macrocode}
+% The commands for the \texttt{Exercise} environment.
+%    \begin{macrocode}
+\def\beginExerciseEnv{\@InitExe\@ifnextchar[\@@ExeEnv{\@@ExeEnv[]}}%]
+%
+\def\@@ExeEnv[#1]{\setkeys{PPExercise}{#1}%
+\global\@Answerfalse\@BeginExeBox\@@@ExeEnv}
+%
+\newcommand{\@@@ExeEnv}{%
+    \@QuestionLevel1
+    \refstepExecounter
+    \begingroup\@getExerciseInfo\ExerciseHeader\endgroup}
+%
+%
+\def\endExerciseEnv{\termineliste{1}\@EndExeBox}
+%    \end{macrocode}
+% The commands for exercise within <ExerciseList> environment
+%    \begin{macrocode}
+\def\ExerciseCmd{\@InitExe\@ifstar{\global\@ExeStaredtrue\@ExeCmd}%
+{\global\@ExeStaredfalse\@ExeCmd}}
+%
+\def\@ExeCmd{\@ifnextchar[\@@ExeCmd{\@@ExeCmd[]}}%] for emacs
+%
+\def\@@ExeCmd[#1]{\setkeys{PPExercise}{#1}\@@@ExeCmd}
+%
+\newcommand{\@@@ExeCmd}{%
+    \ifnum\@QuestionLevel=0
+      \advance \@QuestionLevel by 1
+      \begin{list}{\@getExerciseInfo\ExerciseListHeader}%
+{\partopsep\Exepartopsep \labelsep\Exelabelsep \itemsep \Exesep%
+\parsep\Exeparsep \topsep\Exetopsep \labelwidth\Exelabelwidth%
+\leftmargin\Exeleftmargin \rightmargin\Exerightmargin}
+    \else
+      \termineliste{1}\@EndExeBox
+    \fi
+    \global\@Answerfalse\@BeginExeBox\refstepExecounter%
+    \item\ignorespaces
+}
+%
+\def\defineExerciseEnv{%
+    \renewenvironment{Exercise}{\global\@ExeStaredfalse\beginExerciseEnv}%
+{\endExerciseEnv}
+    \renewenvironment{Exercise*}{\global\@ExeStaredtrue\beginExerciseEnv}%
+{\endExerciseEnv}
+}
+\newenvironment{Exercise}{}{}
+\newenvironment{Exercise*}{}{}
+%
+\def\defineExerciseCmd{\def\Exercise{\ExerciseCmd}}
+%
+\renewcommand{\Exercise}{}
+%
+\defineExerciseEnv
+%
+\def\beginExerciseListEnv{\defineExerciseCmd\defineAnswerCmd}
+%
+\def\endExerciseListEnv{\termineliste{1}\@EndExeBox\termineliste{0}%
+\defineExerciseEnv\defineAnswerEnv}
+%
+\newenvironment{ExerciseList}{\beginExerciseListEnv}{\endExerciseListEnv}
+%    \end{macrocode}
+% \subsubsection{Definition of \texttt{questions}}
+%    \begin{macrocode}
+\def\QuestionTitle{}
+\newif\if@QuestionTitle              \@QuestionTitlefalse
+\global\newcount\QuestionDifficulty  \QuestionDifficulty=0
+\newif\if@QuestionDifficulty         \@QuestionDifficultyfalse
+%
+\define@key{PPQuestion}{title}{%
+\gdef\QuestionTitle{\string#1}\@QuestionTitletrue}
+\define@key{PPQuestion}{difficulty}{%
+\@QuestionDifficultytrue\global\QuestionDifficulty=\number#1}
+%
+\def\@InitQuestion{\gdef\QuestionTitle{}%
+\global\QuestionDifficulty=0%
+\global\@QuestionTitlefalse%
+\global\@QuestionDifficultyfalse}
+%
+\def\@getQuestionInfo{%
+\if@QuestionTitle\else\def\QuestionHeaderTitle{}\fi
+\if@QuestionDifficulty\else\def\QuestionHeaderDifficulty{}\fi
+}
+%
+\def\EndCurrentQuestion{\termineliste{1}}
+%
+\def\Question{\@InitQuestion\@ifnextchar[\@@Question{\@@Question[]}}%] 
+%
+\def\@@Question[#1]{\setkeys{PPQuestion}{#1}\@@@Question}
+%
+\def\@QuestionHeader{\item[{\makebox[0cm][r]{\begingroup\@getQuestionInfo%
+\QuestionHeaderDifficulty\QuestionNB\endgroup}}]%
+\begingroup\@getQuestionInfo\QuestionHeaderTitle\endgroup\ignorespaces}
+\newcommand{\@@@Question}{%
+    \ifnum\@QuestionLevel=1
+    \advance \@QuestionLevel by 1
+    \begin{list}{}{\leftmargin \QuestionIndent
+            \partopsep0pt \parsep0pt \topsep \QuestionBefore 
+            \itemsep \QuestionBefore \labelwidth 2em
+            \usecounter{Question}}
+        \if@echapq
+          \setcounter{Question}{\value{savedQuestion}}\global\@echapqfalse
+        \fi
+        \refstepcounter{Question}
+        \@restoremathindent
+        \@decalemathindent{\QuestionIndent}
+        \@QuestionHeader
+   \else
+     \ifnum\@QuestionLevel=2
+          \refstepcounter{Question}
+          \@QuestionHeader
+     \else
+     \ifnum\@QuestionLevel>2
+       \termineliste{2}
+       \refstepcounter{Question}
+       \@QuestionHeader
+     \else
+     \PackageError{exercise}{You don't respect the hierarchy of
+         questions}{Verify the Question}
+     \fi
+   \fi
+ \fi
+}
+%    \end{macrocode}
+% \subsubsection{Definition of \texttt{sub-questions} and
+%\texttt{sub-sub-questions}}
+% Here a good factorization is possible, but I prefer readibility over
+% efficacity.
+%    \begin{macrocode}
+\def\subQuestionTitle{}
+\newif\if@subQuestionTitle\@subQuestionTitlefalse
+\global\newcount\subQuestionDifficulty\subQuestionDifficulty=0
+\newif\if@subQuestionDifficulty\@subQuestionDifficultyfalse
+%
+\define@key{PPsubQuestion}{title}{%
+\gdef\subQuestionTitle{\string#1}\@subQuestionTitletrue}
+\define@key{PPsubQuestion}{difficulty}{%
+\@subQuestionDifficultytrue\global\subQuestionDifficulty=\number#1}
+%
+\def\@InitsubQuestion{\gdef\subQuestionTitle{}%
+\global\subQuestionDifficulty=0%
+\global\@subQuestionTitlefalse%
+\global\@subQuestionDifficultyfalse}
+%
+\def\@getsubQuestionInfo{%
+\if@subQuestionTitle\else\def\subQuestionHeaderTitle{}\fi
+\if@subQuestionDifficulty\else\def\subQuestionHeaderDifficulty{}\fi
+}
+%
+\def\EndCurrentsubQuestion{\termineliste{2}}
+%
+\def\subQuestion{\@InitsubQuestion%
+\@ifnextchar[\@@subQuestion{\@@subQuestion[]}}%] 
+\def\@@subQuestion[#1]{\setkeys{PPsubQuestion}{#1}\@@@subQuestion}
+%
+\def\@subQuestionHeader{\item[{\makebox[0cm][r]%
+{\begingroup\@getsubQuestionInfo\subQuestionHeaderDifficulty%
+\subQuestionNB\endgroup}}]%
+\begingroup\@getsubQuestionInfo\subQuestionHeaderTitle\endgroup%
+\ignorespaces}
+\newcommand{\@@@subQuestion}{%
+    \ifnum\@QuestionLevel=2
+    \advance \@QuestionLevel by 1
+    \begin{list}{}{\leftmargin \subQuestionIndent
+            \partopsep0pt \parsep0pt \topsep \subQuestionBefore 
+            \itemsep \subQuestionBefore \labelwidth 2em
+            \usecounter{subQuestion}}
+        \if@echapq
+          \setcounter{subQuestion}{\value{savedsubQuestion}}%
+          \global\@echapqfalse
+        \fi
+        \refstepcounter{subQuestion}
+        \@restoremathindent
+        \@decalemathindent{\subQuestionIndent}
+        \@subQuestionHeader
+   \else
+     \ifnum\@QuestionLevel=3
+          \refstepcounter{subQuestion}
+          \@subQuestionHeader
+     \else
+     \ifnum\@QuestionLevel>3
+       \termineliste{3}
+       \refstepcounter{subQuestion}
+       \@subQuestionHeader
+     \else
+     \PackageError{exercise}{You don't respect the hierarchy of
+         subQuestion}{Verify the subQuestion}
+     \fi
+   \fi
+ \fi
+}
+%
+\def\subsubQuestionTitle{}
+\newif\if@subsubQuestionTitle\@subsubQuestionTitlefalse
+\global\newcount\subsubQuestionDifficulty\subsubQuestionDifficulty=0
+\newif\if@subsubQuestionDifficulty\@subsubQuestionDifficultyfalse
+%
+\define@key{PPsubsubQuestion}{title}{%
+\gdef\subsubQuestionTitle{\string#1}\@QuestionTitletrue}
+\define@key{PPsubsubQuestion}{difficulty}{%
+\@QuestionDifficultytrue\global\subsubQuestionDifficulty=\number#1}
+%
+\def\@InitsubsubQuestion{\gdef\subsubQuestionTitle{}%
+\global\subsubQuestionDifficulty=0%
+\global\@subsubQuestionTitlefalse%
+\global\@subsubQuestionDifficultyfalse}
+%
+\def\@getsubsubQuestionInfo{%
+\if@subsubQuestionTitle\else\def\subsubQuestionHeaderTitle{}\fi
+\if@subsubQuestionDifficulty\else\def\subsubQuestionHeaderDifficulty{}\fi
+}
+%
+\def\EndCurrentsubsubQuestion{\termineliste{3}}
+\def\subsubQuestion{\@InitsubsubQuestion%
+\@ifnextchar[\@@subsubQuestion{\@@subsubQuestion[]}}%] 
+\def\@@subsubQuestion[#1]{\setkeys{PPsubsubQuestion}{#1}\@@@subsubQuestion}
+%
+\def\@subsubQuestionHeader{\item[{\makebox[0cm][r]%
+{\begingroup\@getsubsubQuestionInfo\subsubQuestionHeaderDifficulty%
+\subsubQuestionNB\endgroup}}]%
+\begingroup\@getsubsubQuestionInfo\subsubQuestionHeaderTitle\endgroup%
+\ignorespaces}
+\newcommand{\@@@subsubQuestion}{%
+    \ifnum\@QuestionLevel=3
+    \advance \@QuestionLevel by 1
+    \begin{list}{}{\leftmargin \subsubQuestionIndent
+            \partopsep0pt \parsep0pt \topsep \subsubQuestionBefore 
+            \itemsep \subsubQuestionBefore \labelwidth 2em
+            \usecounter{subsubQuestion}}
+        \if@echapq
+          \setcounter{subsubQuestion}{\value{savedsubsubQuestion}}%
+          \global\@echapqfalse
+        \fi
+        \refstepcounter{subsubQuestion}
+        \@restoremathindent
+        \@decalemathindent{\subsubQuestionIndent}
+        \@subsubQuestionHeader
+   \else
+     \ifnum\@QuestionLevel=4
+          \refstepcounter{subsubQuestion}
+          \@subsubQuestionHeader
+     \else
+     \ifnum\@QuestionLevel>4
+       \termineliste{4}
+       \refstepcounter{subsubQuestion}
+       \@subsubQuestionHeader
+     \else
+     \PackageError{exercise}{You don't respect the hierarchy of
+         subsubQuestion}{Verify the subsubQuestion}
+     \fi
+   \fi
+ \fi
+}
+%    \end{macrocode}
+% \subsubsection{ Presentation of part (within an exercise)}
+%    \begin{macrocode}
+\newif\if@ExePartStared             \@ExePartStaredfalse
+\newif\if@ExePartTitle              \@ExePartTitlefalse
+\newif\if@ExePartReName             \@ExePartReNamefalse
+\newif\if@ExePartDifficulty         \@ExePartDifficultyfalse
+\global\newcount\ExePartDifficulty  \ExePartDifficulty=0
+%
+\def\theExePartDifficulty{\marker{\DifficultyMarker}{\ExePartDifficulty}}
+%
+\def\@InitExePart{\global\@echapqfalse%
+\gdef\ExePartTitle{}%
+\gdef\@ExePartName{}%
+\global\ExePartDifficulty=0%
+\global\@ExePartTitlefalse%
+\global\@ExePartReNamefalse%
+\global\@ExePartDifficultyfalse%
+\setcounter{Question}{0}}
+%
+\define@key{PPExePart}{title}{\gdef\ExePartTitle{\string#1}\@ExePartTitletrue}
+\define@key{PPExePart}{name}{\gdef\@ExePartName{\string#1}\@ExePartReNametrue}
+\define@key{PPExePart}{difficulty}{\@ExePartDifficultytrue%
+\global\ExePartDifficulty=\number#1}
+%
+\def\@getExePartInfo{%
+\if@ExePartReName\def\ExePartName{\@ExePartName}\fi
+\if@ExePartTitle\else\def\ExePartHeaderTitle{}\fi
+\if@ExePartDifficulty\else\def\ExePartHeaderDifficulty{}\fi
+\if@ExePartStared\def\ExePartHeaderNB{}\fi
+}
+%
+\def\ExePart{\@InitExePart\@ifstar{\global\@ExePartStaredtrue\@ExePart}%
+{\global\@ExePartStaredfalse\@ExePart}}
+%
+\def\@ExePart{\@ifnextchar[\@@ExePart{\@@ExePart[]}}%] for emacs
+%
+\def\@@ExePart[#1]{\setkeys{PPExePart}{#1}\@@@ExePart}
+%
+\newcommand{\@@@ExePart}{%
+    \if@ExePartStared\else\refstepcounter{ExePart}\fi
+    \begingroup\@getExePartInfo\ExePartHeader\endgroup}
+%
+%    \end{macrocode}
+% \subsubsection{ Presentation of answers}
+%    \begin{macrocode}
+\newbox\@Answerbox
+%
+%% \newcommand{\AnswerHeaderRef}{Answer of \ExerciseName\ \theExercise}
+%% \newcommand{\AnswerListHeaderRef}{Answer (ex.\ \theExercise)\ ---\ }
+%
+\newcommand{\AnswerHeader}{\medskip\centerline{\textbf{Answer of
+            \ExerciseName  \ExerciseHeaderNB}\smallskip}}
+%
+\newcommand{\AnswerListHeader}{\textbf{Answer (ex.\
+        \ExerciseHeaderNB)\ ---\ }}
+%
+% The commands for <Exercise> environment
+%
+\def\@InitAnswer{\@savemathindent\global\@echapqfalse%
+\gdef\AnswerRef{}%
+\global\@AnswerReffalse%
+\gdef\AnswerNB{}%
+\global\@AnswerNBfalse%
+\setcounter{Question}{0}}
+%
+\def\@getAnswerInfo{%
+\if@AnswerRef%
+\def\AnswerHeader{\ref{PP\AnswerRef}}%
+\def\AnswerListHeader{\ref{PP\AnswerRef}}%
+\else
+\if@AnswerNB
+\def\ExerciseTitle{}
+\def\ExerciseName{}
+\def\ExerciseOrigin{}
+\ExerciseDifficulty=0
+\def\theExercise{\AnswerNB}
+\else
+\if@AswLastExe
+\else
+\PackageWarning{Exercise}%
+{A answer has no reference and no number}{}%
+\def\AnswerHeaderRef{\AnswerName\ ???}%
+\def\AnswerListHeaderRef{\AnswerName\ ???}%
+\fi\fi\fi}
+%
+\newif\if@AnswerRef         \@AnswerReffalse
+\newif\if@AnswerNB          \@AnswerNBfalse
+%
+\define@key{PPAnswer}{ref}{\global\@AnswerReftrue\gdef\AnswerRef{\string#1}}
+\define@key{PPAnswer}{number}{\global\@AnswerNBtrue\gdef\AnswerNB{\string#1}}
+%
+\def\beginAnswerEnv{\@InitAnswer\@ifnextchar[\@@AnswerEnv{\@@AnswerEnv[]}}%]
+%
+\def\@@AnswerEnv[#1]{\setkeys{PPAnswer}{#1}%
+\global\@Answertrue\@BeginExeBox\@@@AnswerEnv}
+%
+\newcommand{\@@@AnswerEnv}{%
+    \@QuestionLevel1
+    \begingroup\@getAnswerInfo\AnswerHeader\endgroup}
+%
+\def\endAnswerEnv{\termineliste{1}\@EndExeBox}
+%
+\newenvironment{Answer}{}{}
+\def\defineAnswerEnv{
+    \gdef\@AnswerHeaderRef{\AnswerHeader}
+    \renewenvironment{Answer}{\beginAnswerEnv}{\endAnswerEnv}}
+%
+\defineAnswerEnv
+%
+\def\AnswerCmd{\@InitAnswer\@ifnextchar[\@@AnswerCmd{\@@AnswerCmd[]}}
+%
+\def\@@AnswerCmd[#1]{\setkeys{PPAnswer}{#1}\@@@AnswerCmd}
+%
+\newcommand{\@@@AnswerCmd}{%
+    \ifnum\@QuestionLevel=0
+      \advance \@QuestionLevel by 1
+      \begin{list}{}{\partopsep\Exepartopsep \labelsep\Exelabelsep 
+                     \itemsep \Exesep \parsep\Exeparsep 
+                     \topsep\Exetopsep \labelwidth\Exelabelwidth 
+                     \leftmargin\Exeleftmargin
+                     \rightmargin\Exerightmargin }
+                 \refstepExecounter
+    \else
+      \termineliste{1}\@EndExeBox
+    \fi
+    \global\@Answertrue\@BeginExeBox%
+        \item[\bgroup\@getAnswerInfo\AnswerListHeader\egroup]\ignorespaces
+}
+%
+\def\defineAnswerCmd{\gdef\@AnswerHeaderRef{\AnswerListHeader}%
+\gdef\Answer{\AnswerCmd}}
+%    \end{macrocode}
+% \subsubsection{ Some extra stuff}
+%    \begin{macrocode}
+\newcommand{\ExeText}{\setcounter{savedQuestion}{\value{Question}}%
+\termineliste{1}\@echapqtrue}
+%    \end{macrocode}
+% \subsubsection{Secret stuff}
+%    \begin{macrocode}
+%
+% Il est possible de présenter un niveau de sectionnement sur
+% deux colonnes avec la commande \colonnesLevel
+%
+\newcount\colonnesLevel \colonnesLevel=-10
+\newskip\tempskipa
+\newskip\tempskipb
+\def\deuxcolonnes{\tempskipa=\multicolsep\colonnesLevel=\@QuestionLevel
+\ifcase\@QuestionLevel \multicolsep=\QuestionBefore %
+\or
+\multicolsep=\subQuestionBefore\or\multicolsep=\subsubQuestionBefore\fi%
+\begin{multicols}{2}}
+%
+% Tenir compte de l'option fleqn
+%
+\@ifundefined{if@fleqn}{\newif\if@fleqn\@fleqnfalse}{} 
+%
+\newcommand{\@savemathindent}{\relax}
+\newcommand{\@decalemathindent}[1]{\relax}
+\newcommand{\@restoremathindent}{\relax}
+\if@fleqn %
+  \renewcommand{\@savemathindent}{\setlength{\@savedmathindent}{\mathindent}}
+  \renewcommand{\@decalemathindent}[1]{\addtolength{\mathindent}{#1}}
+  \renewcommand{\@restoremathindent}{\setlength{\mathindent}{\@savedmathindent}}
+\else
+  \renewcommand{\@savemathindent}{\relax}
+  \renewcommand{\@decalemathindent}[1]{\relax}
+  \renewcommand{\@restoremathindent}{\relax}
+\fi
+%    \end{macrocode}
+% \subsection{The \texttt{\textbackslash renewcounter} command}
+% This commands is the equivalent of the well--known |\renewcommand|,
+% but for counter. It allows you to redefine the |Exercise| counter,
+% in order to reset it at each chapter (for example).
+%    \begin{macrocode}
+\def\renewcounter#1{%
+    \@ifundefined{c@#1}
+    {\@latex@error{counter #1 undefined}\@ehc}%
+    \relax
+    \let\@ifdefinable\@rc@ifdefinable
+    \@ifnextchar[{\@newctr{#1}}{}}
+%    \end{macrocode}
+% \Finale
+\endinput
diff --git a/Master/texmf-dist/source/latex/exercise/exercise.ins b/Master/texmf-dist/source/latex/exercise/exercise.ins
new file mode 100644
index 00000000000..57d5817637f
--- /dev/null
+++ b/Master/texmf-dist/source/latex/exercise/exercise.ins
@@ -0,0 +1,66 @@
+%% Copyright (C) 2003 by Paul Pichaureau 

+%%

+%% This program is free software; you can redistribute it and/or

+%% modify it under the terms of the GNU General Public License

+%% as published by the Free Software Foundation; either version 2

+%% of the License, or (at your option) any later version.

+%%

+%% This program is distributed in the hope that it will be useful,

+%% but WITHOUT ANY WARRANTY; without even the implied warranty of

+%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

+%% GNU General Public License for more details.

+%%

+%% You should have received a copy of the GNU General Public License

+%% along with this program; if not, write to the Free Software

+%% Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

+%% Public LaTeX Project Public

+

+\input docstrip.tex

+

+%\keepsilent

+

+\usedir{tex/latex/exercise}

+

+\preamble

+

+This is a generated file.

+

+Copyright (C) 2003 by Paul Pichaureau 

+

+This program is free software; you can redistribute it and/or

+modify it under the terms of the GNU General Public License

+as published by the Free Software Foundation; either version 2

+of the License, or (at your option) any later version.

+

+This program is distributed in the hope that it will be useful,

+but WITHOUT ANY WARRANTY; without even the implied warranty of

+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

+GNU General Public License for more details.

+

+You should have received a copy of the GNU General Public License

+along with this program; if not, write to the Free Software

+Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

+Public LaTeX Project Public

+

+\endpreamble

+

+\generate{\file{exercise.sty}{\from{exercise.dtx}{package}}}

+

+\Msg{*********************************************************}

+\Msg{*}

+\Msg{* To finish the installation you have to move the}

+\Msg{* following file into a directory searched by TeX:}

+\Msg{*}

+\Msg{* \space\space exercise.sty}

+\Msg{*}

+\Msg{* To produce the documentation run the file exercise.dtx}

+\Msg{* through LaTeX.}

+\Msg{*}

+\Msg{* Don't forget to produce Index and Change History with}

+\Msg{*   makeindex -s gind.ist -o exercise.ind exercise.idx}

+\Msg{*   makeindex -s gglo.ist -o exercise.gls exercise.glo}

+\Msg{*}

+\Msg{* Happy TeXing!}

+\Msg{*********************************************************}

+

+\endbatchfile
\ No newline at end of file