86f6a31e |
1 | % \begin{meta-comment} |
2 | % |
3 | % $Id: exercise.dtx,v 1.1 2002/02/03 20:49:03 mdw Exp $ |
4 | % |
5 | % Exercises |
6 | % |
7 | % (c) 2001 Mark Wooding |
8 | % |
9 | %----- Revision history ----------------------------------------------------- |
10 | % |
11 | % $Log: exercise.dtx,v $ |
12 | % Revision 1.1 2002/02/03 20:49:03 mdw |
13 | % Checkin for new build system. |
14 | % |
15 | % |
16 | % \end{meta-comment} |
17 | % |
18 | % \begin{meta-comment} <general public licence> |
19 | %% |
20 | %% exercise package -- useful macros for setting exercises with answers |
21 | %% Copyright (c) 2001 Mark Wooding |
22 | %% |
23 | %% This program is free software; you can redistribute it and/or modify |
24 | %% it under the terms of the GNU General Public License as published by |
25 | %% the Free Software Foundation; either version 2 of the License, or |
26 | %% (at your option) any later version. |
27 | %% |
28 | %% This program is distributed in the hope that it will be useful, |
29 | %% but WITHOUT ANY WARRANTY; without even the implied warranty of |
30 | %% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
31 | %% GNU General Public License for more details. |
32 | %% |
33 | %% You should have received a copy of the GNU General Public License |
34 | %% along with this program; if not, write to the Free Software Foundation, |
35 | %% Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
36 | % \end{meta-comment} |
37 | % |
38 | % \begin{meta-comment} <Package preambles> |
39 | %<+package>\NeedsTeXFormat{LaTeX2e} |
40 | %<+package>\ProvidesPackage{exercise} |
41 | %<+package> [2001/09/21 1.0 Exercies with answers] |
42 | % \end{meta-comment} |
43 | % |
44 | % \CheckSum{236} |
45 | %% \CharacterTable |
46 | %% {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 |
47 | %% 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 |
48 | %% Digits \0\1\2\3\4\5\6\7\8\9 |
49 | %% Exclamation \! Double quote \" Hash (number) \# |
50 | %% Dollar \$ Percent \% Ampersand \& |
51 | %% Acute accent \' Left paren \( Right paren \) |
52 | %% Asterisk \* Plus \+ Comma \, |
53 | %% Minus \- Point \. Solidus \/ |
54 | %% Colon \: Semicolon \; Less than \< |
55 | %% Equals \= Greater than \> Question mark \? |
56 | %% Commercial at \@ Left bracket \[ Backslash \\ |
57 | %% Right bracket \] Circumflex \^ Underscore \_ |
58 | %% Grave accent \` Left brace \{ Vertical bar \| |
59 | %% Right brace \} Tilde \~} |
60 | %% |
61 | % |
62 | % \begin{meta-comment} |
63 | % |
64 | %<*driver> |
65 | \input{mdwtools} |
66 | \describespackage{exercise} |
67 | \let\epsilon\varepsilon |
68 | \mdwdoc |
69 | %</driver> |
70 | % |
71 | % \end{meta-comment} |
72 | % |
73 | %^^A------------------------------------------------------------------------- |
74 | % \section{User guide} |
75 | % |
76 | % The \package{exercise} package allows you to typeset exercises and keep the |
77 | % answers together with the questions in your source (so they don't get |
78 | % lost) but typeset them all together at the end of your document. |
79 | % |
80 | % \subsection{Exercises and answers} |
81 | % |
82 | % \DescribeEnv{exercise} |
83 | % Exercises are typset in an \env{exercise} environment. This takes no |
84 | % arguments. There's a counter for exercises, named |exercise|, and you can |
85 | % cross-reference exercises in the usual way. |
86 | % |
87 | % \DescribeMacro\answer |
88 | % If you want to include an answer for your exercise, just say |\answer| |
89 | % followed by your answer. The rest of the text up to the end of the |
90 | % \env{exercise} environment is considered to be the answer, and is stored |
91 | % away until asked for. This material can contain anything you like. It |
92 | % \emph{isn't} a moving argument. |
93 | % |
94 | % \begin{figure} |
95 | %\begin{demo}[w]{The \env{exercise} environment} |
96 | %\begin{exercise} |
97 | %Show that if $F\colon \{0, 1\}^k \times \{0, 1\}^* \to \{0, 1\}^L$ |
98 | %is a $(t, q + 1, \epsilon)$-secure PRF, then $F$~is also a |
99 | %$(t, q, \epsilon + 2^{-L})$-secure MAC. |
100 | %\answer |
101 | %Let~$A$ be an adversary attacking~$F$ as a MAC. Consider the |
102 | %adversary~$B$ \ldots |
103 | %\end{exercise} |
104 | %\end{demo} |
105 | % \end{figure} |
106 | % |
107 | % \subsection{The answers file} |
108 | % |
109 | % \DescribeMacro\answrite |
110 | % Answers are accumulated into a file, to be read later. Additional material |
111 | % can be added to the file using the |\answrite| macro, which just writes its |
112 | % argument. Note that this is a \emph{moving} argument, so fragile commands |
113 | % need |\protect|ing. |
114 | % |
115 | % \DescribeMacro\exctrcheck |
116 | % It's common to divide up the answers by section. You can tell the package |
117 | % to check a collection of counters and perform actions if they've changed |
118 | % since last time, giving you a chance to write the correct decorations to |
119 | % the answers file. This is done by saying |
120 | % \syntax{"\\exctrcheck{"<counter>"}{"<action>"}"}. Then, each |\answer| |
121 | % command checks to see if \<counter> has changed since last time, and if it |
122 | % has, it does \<action>, For example, |
123 | %\begin{verbatim} |
124 | %\exctrcheck{section} |
125 | % {\answrite{\protect\subsection*{Section \thesection}}} |
126 | %\end{verbatim} |
127 | % starts a new (unnumbered) subsection in the answers for each section in the |
128 | % main document. |
129 | % |
130 | % \subsection{Style tweaks} |
131 | % |
132 | % The \env{exercise} environment is very simple, and can be easily rewritten |
133 | % to fit in with your style preferences. If you like exercises to look like |
134 | % theorems, the easiest thing to do is say something like |
135 | %\begin{verbatim} |
136 | %\newtheorem{doexercise}[exercise]{\exercisename} |
137 | %\renewenvironment{exercise}{\exfix\doexercise}{\enddoexercise} |
138 | %\end{verbatim} |
139 | % This makes the environment use the existing exercise counter. If you don't |
140 | % want that, say |
141 | %\begin{verbatim} |
142 | %\newtheorem{doexercise}[othercounter]{\exercisename} |
143 | %\renewenvironment{exercise}{\exfix\doexercise}{\enddoexercise} |
144 | %\let\theexercise\theothercounter |
145 | %\end{verbatim} |
146 | % and all will be well. |
147 | % |
148 | % \DescribeEnv{doanswer} |
149 | % Answers are typeset in a \env{doanswer} environment, which is given one |
150 | % argument: the exercise number (as set by |\theexercise|). This can be |
151 | % modified to do whatever you like. |
152 | % |
153 | % \DescribeMacro\exfix |
154 | % The |\exfix| is a convenient hook which is run both in the \env{exercise} |
155 | % and \env{doanswer} environments by default. The current implementation |
156 | % just skips a level of \env{enumerate} depth, which usually means that |
157 | % \env{enumerate} lists will go (a), (b), (c), \ldots\ rather than 1, 2, 3, |
158 | % \ldots |
159 | % |
160 | % \subsection{Lists in paragraphs} |
161 | % |
162 | % \DescribeEnv{parenum} |
163 | % Answers to subparts tend to be compressed together into a single |
164 | % paragraph. It's nice, when you do this, not to have to worry about losing |
165 | % your numbering of subparts. The \env{parenum} environment provides an |
166 | % enumerated list in a paragraph. So, for example, you can say something |
167 | % like this. |
168 | %\begin{demo}[w]{Example of \env{parenum}} |
169 | %\begin{exercise} |
170 | %A PRG $g\colon \{0, 1\}^k \to \{0, 1\}^L$ is \emph{trivial} if |
171 | %$k \ge L$. |
172 | %\begin{enumerate} |
173 | %\item Show that trivial PRGs exist. |
174 | %\item Show that a non-trivial $(t, \epsilon)$-secure PRG is a |
175 | % $(t, \epsilon + 2^{k-L})$-secure one-way function. |
176 | %\end{enumerate} |
177 | %\answer |
178 | %\begin{parenum} |
179 | %\item The identity function is a trivial PRG: the real and random |
180 | % games are identically distributed. |
181 | %\item Let~$A$ be an adversary attempting to invert~$g$: then we |
182 | % can construct a distinguisher~$B$ as follows \ldots |
183 | %\end{parenum} |
184 | %\end{exercise} |
185 | %\end{demo} |
186 | % |
187 | % \subsection{And finally} |
188 | % |
189 | % \DescribeMacro\answers |
190 | % In order to extract your answers, say |\answers|. |
191 | %\begin{demo}[w]{The \texttt{\string\answers} command} |
192 | %\section*{Answers} |
193 | %\answers |
194 | %\end{demo} |
195 | % |
196 | % \implementation |
197 | % |
198 | % |
199 | %^^A------------------------------------------------------------------------- |
200 | % \section{Implementation} |
201 | % |
202 | % \begin{macrocode} |
203 | %<*package> |
204 | % \end{macrocode} |
205 | % |
206 | % \subsection{Initialization} |
207 | % |
208 | % The \textsf{within} option is handled by the \package{keyval} package. |
209 | % |
210 | % \begin{macrocode} |
211 | \RequirePackage{keyval} |
212 | % \end{macrocode} |
213 | % |
214 | % \begin{macro}{\ex@within} |
215 | % |
216 | % When the \textsf{within} option is seen, we set a command |\ex@within| to |
217 | % the correct code, to be executed later when we've made our minds up. |
218 | % |
219 | % \begin{macrocode} |
220 | \let\ex@within\relax |
221 | \define@key{ex}{within}{% |
222 | \def\ex@within{% |
223 | \@addtoreset{exercise}{#1}% |
224 | \toks@\expandafter{\csname the#1\expandafter\endcsname% |
225 | \expandafter.\theexercise}% |
226 | \edef\theexercise{\the\toks@}% |
227 | }% |
228 | } |
229 | % \end{macrocode} |
230 | % \end{macro} |
231 | % |
232 | % \begin{macro}{\ex@opts} |
233 | % |
234 | % The |\ex@opts| macro just runs the \package{keyval} kit to parse an option |
235 | % string. |
236 | % |
237 | % \begin{macrocode} |
238 | \def\ex@opts{\setkeys{ex}} |
239 | % \end{macrocode} |
240 | % \end{macro} |
241 | % |
242 | % Now do the options thing. |
243 | % |
244 | % \begin{macrocode} |
245 | \DeclareOption*{\expandafter\ex@opts\expandafter{\CurrentOption}} |
246 | \ProcessOptions* |
247 | % \end{macrocode} |
248 | % |
249 | % Set up the |exercise| counter, and number it within some other sort of |
250 | % counter as appropriate. |
251 | % |
252 | % \begin{macrocode} |
253 | \newcounter{exercise}\ex@within |
254 | % \end{macrocode} |
255 | % |
256 | % We also need the \package{sverb} package in order to do the delaying of the |
257 | % answers. |
258 | % |
259 | % \begin{macrocode} |
260 | \RequirePackage{sverb} |
261 | % \end{macrocode} |
262 | % |
263 | % \subsection{Checking for counter changes} |
264 | % |
265 | % \begin{macro}{\ex@ctrcheck} |
266 | % |
267 | % The counter checking state is stored here. It's initially empty. |
268 | % |
269 | % \begin{macrocode} |
270 | \def\ex@ctrcheck{} |
271 | % \end{macrocode} |
272 | % \end{macro} |
273 | % |
274 | % \begin{macro}{\exctrcheck} |
275 | % |
276 | % Adding a counter to the check list is relatively easy. We expand the |
277 | % current list into a token register, add the new material to the end, and |
278 | % put the list back in our macro using |\edef|. The `last' value of the |
279 | % counter is set to |\relax|, to force out the change on the next |\answer|. |
280 | % |
281 | % \begin{macrocode} |
282 | \def\exctrcheck#1#2{% |
283 | \toks@\expandafter{\ex@ctrcheck\ex@ctrdo{#1}{#2}}% |
284 | \edef\ex@ctrcheck{\the\toks@}% |
285 | \global\expandafter\let\csname ex@ctrlast@#1\endcsname\relax% |
286 | } |
287 | % \end{macrocode} |
288 | % \end{macro} |
289 | % |
290 | % \begin{macro}{\ex@ctrdo} |
291 | % |
292 | % Here we actually check to see whether a counter has changed and execute the |
293 | % appropriate code. |
294 | % |
295 | % \begin{macrocode} |
296 | \def\ex@ctrdo#1#2{% |
297 | \edef\@tempa{\csname the#1\endcsname}% |
298 | \expandafter\ifx\csname ex@ctrlast@#1\endcsname\@tempa\else% |
299 | #2% |
300 | \global\expandafter\let\csname ex@ctrlast@#1\endcsname\@tempa% |
301 | \fi% |
302 | } |
303 | % \end{macrocode} |
304 | % \end{macro} |
305 | % |
306 | % \subsection{The \env{exercise} environment} |
307 | % |
308 | % \begin{macro}{\exercisename} |
309 | % |
310 | % We store the string to print for each exercise in |\exercisename| as a |
311 | % half-hearted attempt at internationalization. |
312 | % |
313 | % \begin{macrocode} |
314 | \providecommand\exercisename{Exercise} |
315 | % \end{macrocode} |
316 | % \end{macro} |
317 | % |
318 | % \begin{macro}{\exfix} |
319 | % |
320 | % This is a dumping ground for style fixing common to both exercises and |
321 | % answers. Here, we bump on the \env{enum} depth counter, so that it skips |
322 | % labelling with digits. |
323 | % |
324 | % \begin{macrocode} |
325 | \def\exfix{\advance\@enumdepth\@ne} |
326 | % \end{macrocode} |
327 | % \end{macro} |
328 | % |
329 | % \begin{environment}{exercise} |
330 | % |
331 | % This is pretty simple. The environment is list-based, with the number set |
332 | % in bold in a label. |
333 | % |
334 | % \begin{macrocode} |
335 | \def\exercise{% |
336 | \refstepcounter{exercise}% |
337 | \exfix% |
338 | \trivlist\advance\itemindent\labelsep% |
339 | \item[\textbf{\exercisename\ \theexercise}]% |
340 | } |
341 | \let\endexercise\endtrivlist |
342 | % \end{macrocode} |
343 | % \end{environment} |
344 | % |
345 | % \subsection{Answers} |
346 | % |
347 | % We need a file in which to store our answers. |
348 | % |
349 | % \begin{macrocode} |
350 | \newwrite\ex@ansfile |
351 | % \end{macrocode} |
352 | % |
353 | % \begin{macro}{\ex@ansfilename} |
354 | % |
355 | % In case anyone has a better idea for a filename than our default, we |
356 | % provide a hook. |
357 | % |
358 | % \begin{macrocode} |
359 | \def\ex@ansfilename{\jobname.ans} |
360 | % \end{macrocode} |
361 | % \end{macro} |
362 | % |
363 | % We open the file at the end of the preamble, to give the user a chance to |
364 | % say |\nofiles|, or change |\ex@ansfilename|. |
365 | % |
366 | % \begin{macrocode} |
367 | \AtBeginDocument{% |
368 | \if@filesw% |
369 | \immediate\openout\ex@ansfile=\ex@ansfilename\relax% |
370 | \answrite\relax% |
371 | \fi% |
372 | } |
373 | % \end{macrocode} |
374 | % |
375 | % \begin{macro}{\answrite} |
376 | % |
377 | % This writes stuff to the answers file. We make sure that it's |
378 | % appropriately protected, so that you can insert section headings and so on. |
379 | % |
380 | % \begin{macrocode} |
381 | \def\answrite#1{% |
382 | \if@filesw% |
383 | \begingroup% |
384 | \let\protect\@unexpandable@protect% |
385 | \immediate\write\ex@ansfile{#1}% |
386 | \endgroup% |
387 | \fi% |
388 | } |
389 | % \end{macrocode} |
390 | % \end{macro} |
391 | % |
392 | % \begin{macro}{\answer} |
393 | % |
394 | % The |\answer| macro needs to read until the end of the enclosing |
395 | % \env{exercise} environment (or whatever). |
396 | % |
397 | % \begin{macrocode} |
398 | \def\answer{\sv@readenv\ex@answer} |
399 | % \end{macrocode} |
400 | % |
401 | % Now for the main guts. |
402 | % |
403 | % \begin{macrocode} |
404 | \def\ex@answer#1#2{% |
405 | \begingroup% |
406 | \@bsphack% |
407 | % \end{macrocode} |
408 | % |
409 | % First of all, check to see whether any counters have changed. |
410 | % |
411 | % \begin{macrocode} |
412 | \ex@ctrcheck% |
413 | % \end{macrocode} |
414 | % |
415 | % Start a \env{doanswer} environment in the file. |
416 | % |
417 | % \begin{macrocode} |
418 | \answrite{\noexpand\begin{doanswer}{\theexercise}}% |
419 | % \end{macrocode} |
420 | % |
421 | % Set catcodes to be strange, and read lines one-at-a-time, writing them to |
422 | % the file. When finished, continue at |\ex@endanswer|. |
423 | % |
424 | % \begin{macrocode} |
425 | \let\do\@makeother\dospecials% |
426 | \sv@safespc% |
427 | \sv@read{#1}\answrite{\ex@endanswer#2}% |
428 | } |
429 | % \end{macrocode} |
430 | % |
431 | % When that's done, we wind up here. |
432 | % |
433 | % \begin{macrocode} |
434 | \def\ex@endanswer{% |
435 | \@esphack% |
436 | \answrite{\noexpand\end{doanswer}}% |
437 | \endgroup% |
438 | } |
439 | % \end{macrocode} |
440 | % \end{macro} |
441 | % |
442 | % \begin{macro}{\answers} |
443 | % |
444 | % The |\answers| macro closes the file, makes sure that future |
445 | % \env{exercise}s with answers cause an error, and reads in the file. |
446 | % |
447 | % \begin{macrocode} |
448 | \def\answers{% |
449 | \immediate\closeout\ex@ansfile% |
450 | \global\let\answrite\exerr@toolate% |
451 | \input{\ex@ansfilename}% |
452 | } |
453 | % \end{macrocode} |
454 | % \end{macro} |
455 | % |
456 | % \begin{environment}{doanswer} |
457 | % |
458 | % A very simple environment. We set the exercise number in bold and then |
459 | % just write the text. |
460 | % |
461 | % \begin{macrocode} |
462 | \def\doanswer#1{% |
463 | \exfix% |
464 | \trivlist\advance\itemindent\labelsep% |
465 | \item[\textbf{#1}]% |
466 | } |
467 | \let\enddoanswer\endtrivlist |
468 | % \end{macrocode} |
469 | % \end{environment} |
470 | % |
471 | % \subsection{Lists inside paragraphs} |
472 | % |
473 | % \begin{environment}{parlist} |
474 | % |
475 | % The \env{parlist} environment is a trimmed-down version of a normal list. |
476 | % We todge the |\item| command, make |\list| and |\trivlist| make errors, and |
477 | % do various normal list things. |
478 | % |
479 | % \begin{macrocode} |
480 | \def\parlist#1#2{% |
481 | \let\@trivlist\exerr@parlist% |
482 | \def\@itemlabel{#1}% |
483 | \let\makelabel\relax% |
484 | \@nmbrlistfalse% |
485 | #2% |
486 | \let\item\pl@item% |
487 | \ignorespaces% |
488 | } |
489 | % \end{macrocode} |
490 | % \end{environment} |
491 | % |
492 | % \begin{macro}{\pl@item} |
493 | % |
494 | % This is the implementation of |\item| within a \env{parlist}. The main |
495 | % interesting point is the game with boxes, which has the objective of |
496 | % extracting the text of the item, together with any style changes set by |
497 | % |\makelabel|, but without any stupid bits of glue, or |\llap| or anything |
498 | % like that. |
499 | % |
500 | % \begin{macrocode} |
501 | \def\pl@item{\@ifnextchar[\pl@item@i{\pl@item@i[\@itemlabel]}} |
502 | \def\pl@item@i[#1]{% |
503 | \if@nmbrlist\refstepcounter{\@listctr}\fi% |
504 | \setbox\z@\hbox{\makelabel{\global\setbox\@ne\hbox{#1}}}% |
505 | \ifvmode\leavevmode\else\unskip\hskip1em\fi\box\@ne~\ignorespaces% |
506 | } |
507 | % \end{macrocode} |
508 | % \end{macro} |
509 | % |
510 | % \begin{macro}{\useparlist} |
511 | % |
512 | % We just set the \env{list} environment to use \env{parlist}. |
513 | % |
514 | % \begin{macrocode} |
515 | \def\useparlist{\let\list\parlist\let\endlist\relax} |
516 | % \end{macrocode} |
517 | % \end{macro} |
518 | % |
519 | % \begin{environment}{parenum} |
520 | % |
521 | % Very simple, this. Note that we don't run |\endenumerate|, because that's |
522 | % |\let| to |\endlist|. |
523 | % |
524 | % \begin{macrocode} |
525 | \def\parenum{\useparlist\enumerate} |
526 | \let\endparenum\endparlist |
527 | % \end{macrocode} |
528 | % \end{environment} |
529 | % |
530 | % \subsection{Errors} |
531 | % |
532 | % \begin{macrocode} |
533 | \def\exerr@toolate{% |
534 | \PackageError{exercise}{Too late now for \string\answrite}{% |
535 | You can't write answers after you've read the file in. I've^^J% |
536 | ignored the text you attempted to write. This is why answers^^J% |
537 | go at the end of a book!% |
538 | }% |
539 | } |
540 | \def\exerr@parlist{% |
541 | \PackageError{exercise}{You can't nest a `list' inside a `parlist'.}{% |
542 | I've found a `list' or `trivlist' environment nested inside^^J% |
543 | a `parlist'. This isn't allowed.% |
544 | }% |
545 | } |
546 | %</package> |
547 | % \end{macrocode} |
548 | % |
549 | % Done. |
550 | % |
551 | % \hfill Mark Wooding, \today |
552 | % |
553 | % \Finale |
554 | % |
555 | \endinput |