Sending
Answers to Exercises
(or Proofs of Theorems)
to appendices
(Version v0.92, last modified 2000/23/02)
Didier Rémy
Abstract:
This package provides macros for writing exercises and answers to
exercises. Then, the same document can be run in several modes, for
instance, the answers may be hidden, inserted on place, or just collected
in an auxilliary file to be inserted later in an appendix for instance.
(Then hyperref can be used to make questions and answers point to one
another.)
The package can also be used to send proofs of theorems to appendices.
The package also comes with a version for HEVEA.
This document is also available in
DVI,
Postscript, and
PDF.
The source of this file,
exercise.tex
may serve as an example.
1 The exercise and answer environment
The exercise environment is used to separate and number exercises.
The environment contains an optional parameter meant to be a short
description of the exercise that will then appear as the title of the
exercise, when refered to from another position.
The answer environment is normally used within the exercice
environment, in which case the exercise number is captured and used to refer
to the exercise from another position. There may be several answers within
a single exercise environment. Answers are numbered internally (ie.
independently of any question and subsection structure that the author could
introduce) and its number refers to the n-th answer envrionment from the
beginning of the exercise.
1.1 Collecting answers into an answer-file (default mode)
The default behavior of the answer environment is to copy
the contend of the answer (the region of text between \begin{answer}
and \end{answer} verbatim to the answer file
\ExerciseAnswerFile.ans
(by default \ExerciseAnswerFile is equal to \jobname)
The answer environment can also be used outside of the
exercise environment, in which case the text is inserted verbatim in
the answer file, but without any title and any other side effect. For
instance, this may be used to insert in the answer files some headers or
notes that are global to several exercises.
The fragile command \fragileanswer is an alternative to the use
of the use of the answer environment. However, since it evaluates
its arguments, commands and such must be quoted. The advantage is that it
can be used inside other macros.
The command \inputanswers normally insert all answers to
exercises. It takes the title of the answer section as a mandatory
argument. The base file name of the answer file, may be given as an optional
argument; this allows to load answers generated from another file.
1.2 Customizing answer placements
Customization of answer placement uses the keyval package.
The command \setanswer can be used with the following keys:
noanchors
This will remove hyperref anchors to exercises (which are set by default).
anchors
This will attached hyperref anchors to exercises (if previously removed).
hide
Answers will be hidden.
show
Answers will be shown.
later
If shown, answers will appear later.
inline
If shown, answers will appear immediately.
file=filename
This will use filename as the base name for the answer file.
By default \jobname is used. The suffix .ans will be appended
to the basename. This command key can only be set in the preamble.
The command \inputanswers can be used to insert answers that have been
postponed. The command takes one argument which is used as the title of the
answer section before answers are inserted. The command also takes an
optional argument which is the name of the answer file.
By default the filename if the same one as the one in which answers were
collected. If answers are ignore (as set by the hide key) or
immediate (as set by the inline key) at the time
\inputanswers is executed, then the command is ignored (hence, the
answer section is not created).
These keys can be set globally with the command \setanswers.
The can also be modified globally anywhere or locally in the scope of
grouping parens. Furthermore, they can be set locally to an exercise
by appearing in an optional argument to the exercise environment.
1.3 Package options
The keys noanchors, hide, and
now are also recognized as package options.
Any other package option is interpreted as the argument to the key
file.
1.4 Example
Exercise 1
What would be the effect of the following declaration?
\let \oldsection \section
\renewcommand {\section}[1]
{\oldsection {#1}\fragileanswer
{\string \subsection* {Section \thesection\space (#1)}}}
(Of course the code need improvement to take the optional arguments sections
into account)
Exercise 2
Note that this exercise has no title.
1. what will you see at this place in the main body of the
document?
2. Where will I see the answer to the previous question and to this
one.
Exercise 3 [Hiding answers]
What would happen if I type \setanswer{noanchor} in the body of this
exercise?
And what will happen if I now type \setanswer{hide} in the body of
this exercise?
Exercise 4 [Input Answers]
What will happen if the command \inputanswers is never included?
Note that the file \jobname.ans is only created if non empty.
Thus, if you load the package but do not create any exercise it is not
created. Then, you will simply get a warning if you attempt to load answers
of exercises.
1.5 Customizing the appearance of answers
This can be done by redefining the following commands:
\AnswerSection
The name of the command to print the title of answer section (the argument
of \inputanswers.
\ExerciseName
The identifier used to name exercises (often need to be changed according to
languages). Default value is Exercise, except if
\languagename is frenchb where the value is
Exercice.
\AnswerName
The identifier used to point to answers. Default value is Answer,
except if \languagename is frenchb where the value is
Réponse.
\AnswerNew
The title of an answer to a new exercise. It receives 3 arguments: the exercise
number, the answer number, and the page number.
\AnswerContinued
Idem, but when the answer is not the first one.
AnswerNow
This environment can be redefined to change the typesetting
immediate answers (when answers are immediate, Answer will act as AnswerNow).
2 Creating new answer environments
Further than customization, the user can defined its own answer
environment. For instance, an environment similar to the default
answer of this package can be defined with the following definition:
\newanswer {myanswer}
{\em \AnswerNiceLink}
{}
{\AnswerNow}
{\endAnswerNow}
{{\thepage}}
[1]
{\ifnum \theQuestion=1\relax
\subsection*
{\ExerciseLink {Exercise \theExercise, page #1}}%
\else
\subsubsection*
{\ExerciseLink {Exercice \theExercise\space (continued)}}%
\fi}
{}
The command \newanwer takes at least 8 arguments, with two possible
optional arguments after the fourth one.
-
The first argument is the name of the environment to be
defined.
-
This are will be executed respectively before and after processing the
answer. Typically, they are used to insert a pointer to the exercise in the
appendix.
-
These define the environment that should be used in case the answer is
inserted locally, ie. if
\AnswerLaterfalse is set.
-
This is used to pass information between the place
where the answer environment occurs and the time when the answer will be
reread again. This argument is passed to the
\fragileanswer, ie.
it is evaluated in the local context but inserted in the answer file.
-
The remaining arguments are used to define the behavior of the answer
when reread from the answer file. They are passed to the command
\newenvironment{ans-name} (where name is the name of the
answer-environment being defined) hence the two optional arguments in
case this command used arguments (possibly with default values).
Additionally, the so-created myanswer environment that is
immediately passed to \setanswer for local customization.
This is evaluated first, so that it act as if it \setanswer
were executed outside of the exercise environement, except that the setting
if local to the environment.
More precisely, the following steps are executed at every answer environment
occuring in the text.
-
The argument of the environment is passed to
\setanswer.
Unless the answer is hidden or immediate, the following steps occurs in
order.
-
\begin{exo-answer} is inserted in the answer file.
- The second argument is evaluated.
-
The fourth argument is passed to
\fragileanswer.
-
The answer text is inserted verbatim into the answer file.
-
The third argument is evaluated.
-
\end{exo-answer} is inserted in the answer file.
In addition, two commands are available for manipulating anchors:
\AnswerLink can be used in the text to point to the corresponding
answer in the answer section and, conversely, \ExerciseLink can be
used to point to the exercise from the answer section. Both commands take
one argument (the text where to anchor the link).
A more elaborated version \AnswerNiceLink provides
a default typesetting of the answer link. It takes an optional parameter
---the text of the anchor--- equal to \AnswerName by default.
The environment also adjusts the counters \Exercise and
\Question so that their values while reading the answer file is
identical to the value they had when the corresponding answer was processed.
Other counters (such as pages, sections, etc.) must be passed explicitly
using the fourth argument, as described above.
These steps only applies is the answer appears within an exercise,
and if answers are not hidden. Otherwise, the environment behaves as
in the default case.
3 Sending proofs to an appendix
This package can also be used to typeset proofs locally right after
the claims, and have them appear in an appendix.
For instance this can be realized with the following declaration:
\def \capitalize #1{\uppercase {#1}}
\newanswer {proof}
{\def \theExercise {\ThmName}\def \theQuestion {\ThmLabel}%
\if@answer@later
\if@answer@anchor \AnswerLink{\hbox {(See proof in the Appendix)}}\fi%
\else \def \AnswerName {Proof}\fi
\pdf@hypertarget {Thm-\ThmName.\ThmLabel}{}}
{}
{\trivlist \item [\hskip \labelsep {\underline {Proof}:}]}
{\penalty 100\hfill\rule{2mm}{2mm}\endtrivlist\@doendpe}
{{\ThmName}{\ThmLabel}}
[2]
{\subsection*
{\pdf@hypertarget {Ans-#1.#2}{Proof} of
\pdf@hyperlink {Thm-#1.#2}{\capitalize #1 #2}}%
\nobreak
}
{}
Note the use of \ThmName and \ThmLabel, which refer to the
name and counters of the last theorem-like environment. They can be
retrieved automatically will the following little hack.
\def \@thm #1#2{%
\refstepcounter {#1}
\xdef \ThmName {\@currenvir}%
\xdef \ThmLabel {\@currentlabel}%
\@ifnextchar [{\@ythm {#1}{#2}}{\@xthm{#1}{#2}}%
}
Then, proofs will be recalled by
\inputanswers {Proof of main results}
Warning!
Although the package can be used to posponed several kind of material to an
appendix using a temporary file, it uses a single file so far. So combining
solutions to exercises and proofs to appendices will not work together
(material would be interlaced). Sometimes interlacing may be desired, but
usually not. In the future, the command should offer the possibility to
send different kind of material to different files.
4 Implementation notes
The implementation is quite simple and short.
The only trick is to undo the active catcodes that might have been done by the
inputencoding package before copying answers to
\ExerciseAnswerFile.ans.
Beware!
However, I found out, that to make it work you also need to tell latex to
recognize 8-bit characters, i.e. to treat ``é'' as such, and not as
``^^e9''. On my redhat 6.1 linux machine, it is sufficient
to set the environment variable LC_ALL=en_US. I do not know any
otherway of making latex print 8-bit characters.
Of course, printing ``^^e9'' instead of ``é'' is quite problematic
with with verbatim code, where the ``^^'' will be taken verbatim and
not as an encoding of an 8-bit character. The solution would them
be to pacth the verbatim mode to keep the meaning of ``^^'' as
encoding of 8-bit charaters.
Another, probably simpler, solution would then be to post-process the
answer file to recode 7-bit charaters into 8-bit characters. However, one
cannot reread the reshly created answer file. Instead two different names
for the output and input answer files should be used.
5 HeVeA compatibility
The package also comes with some HEVEA version.
HEVEA asumes that the file has first been processed by tex so that
\jobname.ans already exists.
However, HEVEA does not currently interpret package options.
So, you must set the corresponding flags by hand, instead, to ensure
HEVEA compatibility.
to change
the name of \jobname does not currently work in HEVEA, so you
will have to do the appropriate renaming by hand (or in a Makefile).
The HEVEA version is designed to be combined with hacha:
in addition to pointing to answers, the answers are also included
immediately, but in a separate cutting unit, so that hacha will put them in
an auxilliary file.
This document was translated from LATEX by
HEVEA and HACHA.