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1 | % \begin{meta-comment} |
2 | % |
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3 | % $Id: exercise.dtx,v 1.2 2003/09/05 16:10:41 mdw Exp $ |
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4 | % |
5 | % Exercises |
6 | % |
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7 | % (c) 2003 Mark Wooding |
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8 | % |
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9 | % \end{meta-comment} |
10 | % |
11 | % \begin{meta-comment} <general public licence> |
12 | %% |
13 | %% exercise package -- useful macros for setting exercises with answers |
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14 | %% Copyright (c) 2003 Mark Wooding |
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15 | %% |
16 | %% This program is free software; you can redistribute it and/or modify |
17 | %% it under the terms of the GNU General Public License as published by |
18 | %% the Free Software Foundation; either version 2 of the License, or |
19 | %% (at your option) any later version. |
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20 | %% |
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21 | %% This program is distributed in the hope that it will be useful, |
22 | %% but WITHOUT ANY WARRANTY; without even the implied warranty of |
23 | %% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
24 | %% GNU General Public License for more details. |
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25 | %% |
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26 | %% You should have received a copy of the GNU General Public License |
27 | %% along with this program; if not, write to the Free Software Foundation, |
28 | %% Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
29 | % \end{meta-comment} |
30 | % |
31 | % \begin{meta-comment} <Package preambles> |
32 | %<+package>\NeedsTeXFormat{LaTeX2e} |
33 | %<+package>\ProvidesPackage{exercise} |
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34 | %<+package> [2003/08/25 1.1 Exercies with answers] |
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35 | % \end{meta-comment} |
36 | % |
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37 | % \CheckSum{271} |
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38 | %% \CharacterTable |
39 | %% {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 |
40 | %% 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 |
41 | %% Digits \0\1\2\3\4\5\6\7\8\9 |
42 | %% Exclamation \! Double quote \" Hash (number) \# |
43 | %% Dollar \$ Percent \% Ampersand \& |
44 | %% Acute accent \' Left paren \( Right paren \) |
45 | %% Asterisk \* Plus \+ Comma \, |
46 | %% Minus \- Point \. Solidus \/ |
47 | %% Colon \: Semicolon \; Less than \< |
48 | %% Equals \= Greater than \> Question mark \? |
49 | %% Commercial at \@ Left bracket \[ Backslash \\ |
50 | %% Right bracket \] Circumflex \^ Underscore \_ |
51 | %% Grave accent \` Left brace \{ Vertical bar \| |
52 | %% Right brace \} Tilde \~} |
53 | %% |
54 | % |
55 | % \begin{meta-comment} |
56 | % |
57 | %<*driver> |
58 | \input{mdwtools} |
59 | \describespackage{exercise} |
60 | \let\epsilon\varepsilon |
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61 | \errorcontextlines\maxdimen |
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62 | \mdwdoc |
63 | %</driver> |
64 | % |
65 | % \end{meta-comment} |
66 | % |
67 | %^^A------------------------------------------------------------------------- |
68 | % \section{User guide} |
69 | % |
70 | % The \package{exercise} package allows you to typeset exercises and keep the |
71 | % answers together with the questions in your source (so they don't get |
72 | % lost) but typeset them all together at the end of your document. |
73 | % |
74 | % \subsection{Exercises and answers} |
75 | % |
76 | % \DescribeEnv{exercise} |
77 | % Exercises are typset in an \env{exercise} environment. This takes no |
78 | % arguments. There's a counter for exercises, named |exercise|, and you can |
79 | % cross-reference exercises in the usual way. |
80 | % |
81 | % \DescribeMacro\answer |
82 | % If you want to include an answer for your exercise, just say |\answer| |
83 | % followed by your answer. The rest of the text up to the end of the |
84 | % \env{exercise} environment is considered to be the answer, and is stored |
85 | % away until asked for. This material can contain anything you like. It |
86 | % \emph{isn't} a moving argument. |
87 | % |
88 | % \begin{figure} |
89 | %\begin{demo}[w]{The \env{exercise} environment} |
90 | %\begin{exercise} |
91 | %Show that if $F\colon \{0, 1\}^k \times \{0, 1\}^* \to \{0, 1\}^L$ |
92 | %is a $(t, q + 1, \epsilon)$-secure PRF, then $F$~is also a |
93 | %$(t, q, \epsilon + 2^{-L})$-secure MAC. |
94 | %\answer |
95 | %Let~$A$ be an adversary attacking~$F$ as a MAC. Consider the |
96 | %adversary~$B$ \ldots |
97 | %\end{exercise} |
98 | %\end{demo} |
99 | % \end{figure} |
100 | % |
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101 | % \DescribeMacro\skipanswer |
102 | % The |\skipanswer| command is similar, but just skips over the answer rather |
103 | % than writing it to the output file. It does nothing at all with counters |
104 | % -- it's as if there was no answer given at all. |
105 | % |
106 | % It's OK to use commands like |\answer| and |\skipanswer| in your own |
107 | % macros as long as they're the \emph{last} token. You can therefore say |
108 | % something like |
109 | %\begin{verbatim} |
110 | %\newcommand{\evenanswer}{% |
111 | % \ifthenelse% |
112 | % {\isodd{\value{exercise}}}% |
113 | % {\answer}% |
114 | % {\skipanswer}% |
115 | %} |
116 | %\end{verbatim} |
117 | % to get just the answers to the odd-numbered problems. (If you don't like |
118 | % \package{ifthen} then you'll need to play with |\expandafter| for a bit.) |
119 | % |
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120 | % \subsection{The answers file} |
121 | % |
122 | % \DescribeMacro\answrite |
123 | % Answers are accumulated into a file, to be read later. Additional material |
124 | % can be added to the file using the |\answrite| macro, which just writes its |
125 | % argument. Note that this is a \emph{moving} argument, so fragile commands |
126 | % need |\protect|ing. |
127 | % |
128 | % \DescribeMacro\exctrcheck |
129 | % It's common to divide up the answers by section. You can tell the package |
130 | % to check a collection of counters and perform actions if they've changed |
131 | % since last time, giving you a chance to write the correct decorations to |
132 | % the answers file. This is done by saying |
133 | % \syntax{"\\exctrcheck{"<counter>"}{"<action>"}"}. Then, each |\answer| |
134 | % command checks to see if \<counter> has changed since last time, and if it |
135 | % has, it does \<action>, For example, |
136 | %\begin{verbatim} |
137 | %\exctrcheck{section} |
138 | % {\answrite{\protect\subsection*{Section \thesection}}} |
139 | %\end{verbatim} |
140 | % starts a new (unnumbered) subsection in the answers for each section in the |
141 | % main document. |
142 | % |
143 | % \subsection{Style tweaks} |
144 | % |
145 | % The \env{exercise} environment is very simple, and can be easily rewritten |
146 | % to fit in with your style preferences. If you like exercises to look like |
147 | % theorems, the easiest thing to do is say something like |
148 | %\begin{verbatim} |
149 | %\newtheorem{doexercise}[exercise]{\exercisename} |
150 | %\renewenvironment{exercise}{\exfix\doexercise}{\enddoexercise} |
151 | %\end{verbatim} |
152 | % This makes the environment use the existing exercise counter. If you don't |
153 | % want that, say |
154 | %\begin{verbatim} |
155 | %\newtheorem{doexercise}[othercounter]{\exercisename} |
156 | %\renewenvironment{exercise}{\exfix\doexercise}{\enddoexercise} |
157 | %\let\theexercise\theothercounter |
158 | %\end{verbatim} |
159 | % and all will be well. |
160 | % |
161 | % \DescribeEnv{doanswer} |
162 | % Answers are typeset in a \env{doanswer} environment, which is given one |
163 | % argument: the exercise number (as set by |\theexercise|). This can be |
164 | % modified to do whatever you like. |
165 | % |
166 | % \DescribeMacro\exfix |
167 | % The |\exfix| is a convenient hook which is run both in the \env{exercise} |
168 | % and \env{doanswer} environments by default. The current implementation |
169 | % just skips a level of \env{enumerate} depth, which usually means that |
170 | % \env{enumerate} lists will go (a), (b), (c), \ldots\ rather than 1, 2, 3, |
171 | % \ldots |
172 | % |
173 | % \subsection{Lists in paragraphs} |
174 | % |
175 | % \DescribeEnv{parenum} |
176 | % Answers to subparts tend to be compressed together into a single |
177 | % paragraph. It's nice, when you do this, not to have to worry about losing |
178 | % your numbering of subparts. The \env{parenum} environment provides an |
179 | % enumerated list in a paragraph. So, for example, you can say something |
180 | % like this. |
181 | %\begin{demo}[w]{Example of \env{parenum}} |
182 | %\begin{exercise} |
183 | %A PRG $g\colon \{0, 1\}^k \to \{0, 1\}^L$ is \emph{trivial} if |
184 | %$k \ge L$. |
185 | %\begin{enumerate} |
186 | %\item Show that trivial PRGs exist. |
187 | %\item Show that a non-trivial $(t, \epsilon)$-secure PRG is a |
188 | % $(t, \epsilon + 2^{k-L})$-secure one-way function. |
189 | %\end{enumerate} |
190 | %\answer |
191 | %\begin{parenum} |
192 | %\item The identity function is a trivial PRG: the real and random |
193 | % games are identically distributed. |
194 | %\item Let~$A$ be an adversary attempting to invert~$g$: then we |
195 | % can construct a distinguisher~$B$ as follows \ldots |
196 | %\end{parenum} |
197 | %\end{exercise} |
198 | %\end{demo} |
199 | % |
200 | % \subsection{And finally} |
201 | % |
202 | % \DescribeMacro\answers |
203 | % In order to extract your answers, say |\answers|. |
204 | %\begin{demo}[w]{The \texttt{\string\answers} command} |
205 | %\section*{Answers} |
206 | %\answers |
207 | %\end{demo} |
208 | % |
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209 | % The |\answers| command has an optional argument, which is the file to read |
210 | % in. This allows you to make `answer booklet' documents, by saying |
211 | % something like |
212 | %\begin{verbatim} |
213 | %\answers[otherdoc] |
214 | %\end{verbatim} |
215 | % If you don't give a file extension, then |.ans| is appended automatically. |
216 | % |
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217 | % \implementation |
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218 | % |
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219 | % |
220 | %^^A------------------------------------------------------------------------- |
221 | % \section{Implementation} |
222 | % |
223 | % \begin{macrocode} |
224 | %<*package> |
225 | % \end{macrocode} |
226 | % |
227 | % \subsection{Initialization} |
228 | % |
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229 | % The \textsf{within} option is handled by the \package{mdwkey} package. |
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230 | % |
231 | % \begin{macrocode} |
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232 | \RequirePackage{mdwkey} |
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233 | % \end{macrocode} |
234 | % |
235 | % \begin{macro}{\ex@within} |
236 | % |
237 | % When the \textsf{within} option is seen, we set a command |\ex@within| to |
238 | % the correct code, to be executed later when we've made our minds up. |
239 | % |
240 | % \begin{macrocode} |
241 | \let\ex@within\relax |
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242 | \mkdef{exercise:opts}{within}{% |
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243 | \def\ex@within{% |
244 | \@addtoreset{exercise}{#1}% |
245 | \toks@\expandafter{\csname the#1\expandafter\endcsname% |
246 | \expandafter.\theexercise}% |
247 | \edef\theexercise{\the\toks@}% |
248 | }% |
249 | } |
250 | % \end{macrocode} |
251 | % \end{macro} |
252 | % |
253 | % \begin{macro}{\ex@opts} |
254 | % |
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255 | % The |\ex@opts| macro just runs the \package{mdwkey} kit to parse an option |
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256 | % string. |
257 | % |
258 | % \begin{macrocode} |
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259 | \def\ex@opts{\mkparse{exercise:opts}} |
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260 | % \end{macrocode} |
261 | % \end{macro} |
262 | % |
263 | % Now do the options thing. |
264 | % |
265 | % \begin{macrocode} |
266 | \DeclareOption*{\expandafter\ex@opts\expandafter{\CurrentOption}} |
267 | \ProcessOptions* |
268 | % \end{macrocode} |
269 | % |
270 | % Set up the |exercise| counter, and number it within some other sort of |
271 | % counter as appropriate. |
272 | % |
273 | % \begin{macrocode} |
274 | \newcounter{exercise}\ex@within |
275 | % \end{macrocode} |
276 | % |
277 | % We also need the \package{sverb} package in order to do the delaying of the |
278 | % answers. |
279 | % |
280 | % \begin{macrocode} |
281 | \RequirePackage{sverb} |
282 | % \end{macrocode} |
283 | % |
284 | % \subsection{Checking for counter changes} |
285 | % |
286 | % \begin{macro}{\ex@ctrcheck} |
287 | % |
288 | % The counter checking state is stored here. It's initially empty. |
289 | % |
290 | % \begin{macrocode} |
291 | \def\ex@ctrcheck{} |
292 | % \end{macrocode} |
293 | % \end{macro} |
294 | % |
295 | % \begin{macro}{\exctrcheck} |
296 | % |
297 | % Adding a counter to the check list is relatively easy. We expand the |
298 | % current list into a token register, add the new material to the end, and |
299 | % put the list back in our macro using |\edef|. The `last' value of the |
300 | % counter is set to |\relax|, to force out the change on the next |\answer|. |
301 | % |
302 | % \begin{macrocode} |
303 | \def\exctrcheck#1#2{% |
304 | \toks@\expandafter{\ex@ctrcheck\ex@ctrdo{#1}{#2}}% |
305 | \edef\ex@ctrcheck{\the\toks@}% |
306 | \global\expandafter\let\csname ex@ctrlast@#1\endcsname\relax% |
307 | } |
308 | % \end{macrocode} |
309 | % \end{macro} |
310 | % |
311 | % \begin{macro}{\ex@ctrdo} |
312 | % |
313 | % Here we actually check to see whether a counter has changed and execute the |
314 | % appropriate code. |
315 | % |
316 | % \begin{macrocode} |
317 | \def\ex@ctrdo#1#2{% |
318 | \edef\@tempa{\csname the#1\endcsname}% |
319 | \expandafter\ifx\csname ex@ctrlast@#1\endcsname\@tempa\else% |
320 | #2% |
321 | \global\expandafter\let\csname ex@ctrlast@#1\endcsname\@tempa% |
322 | \fi% |
323 | } |
324 | % \end{macrocode} |
325 | % \end{macro} |
326 | % |
327 | % \subsection{The \env{exercise} environment} |
328 | % |
329 | % \begin{macro}{\exercisename} |
330 | % |
331 | % We store the string to print for each exercise in |\exercisename| as a |
332 | % half-hearted attempt at internationalization. |
333 | % |
334 | % \begin{macrocode} |
335 | \providecommand\exercisename{Exercise} |
336 | % \end{macrocode} |
337 | % \end{macro} |
338 | % |
339 | % \begin{macro}{\exfix} |
340 | % |
341 | % This is a dumping ground for style fixing common to both exercises and |
342 | % answers. Here, we bump on the \env{enum} depth counter, so that it skips |
343 | % labelling with digits. |
344 | % |
345 | % \begin{macrocode} |
346 | \def\exfix{\advance\@enumdepth\@ne} |
347 | % \end{macrocode} |
348 | % \end{macro} |
349 | % |
350 | % \begin{environment}{exercise} |
351 | % |
352 | % This is pretty simple. The environment is list-based, with the number set |
353 | % in bold in a label. |
354 | % |
355 | % \begin{macrocode} |
356 | \def\exercise{% |
357 | \refstepcounter{exercise}% |
358 | \exfix% |
359 | \trivlist\advance\itemindent\labelsep% |
360 | \item[\textbf{\exercisename\ \theexercise}]% |
361 | } |
362 | \let\endexercise\endtrivlist |
363 | % \end{macrocode} |
364 | % \end{environment} |
365 | % |
366 | % \subsection{Answers} |
367 | % |
368 | % We need a file in which to store our answers. |
369 | % |
370 | % \begin{macrocode} |
371 | \newwrite\ex@ansfile |
372 | % \end{macrocode} |
373 | % |
374 | % \begin{macro}{\ex@ansfilename} |
375 | % |
376 | % In case anyone has a better idea for a filename than our default, we |
377 | % provide a hook. |
378 | % |
379 | % \begin{macrocode} |
380 | \def\ex@ansfilename{\jobname.ans} |
381 | % \end{macrocode} |
382 | % \end{macro} |
383 | % |
384 | % We open the file at the end of the preamble, to give the user a chance to |
385 | % say |\nofiles|, or change |\ex@ansfilename|. |
386 | % |
387 | % \begin{macrocode} |
388 | \AtBeginDocument{% |
389 | \if@filesw% |
390 | \immediate\openout\ex@ansfile=\ex@ansfilename\relax% |
391 | \answrite\relax% |
392 | \fi% |
393 | } |
394 | % \end{macrocode} |
395 | % |
396 | % \begin{macro}{\answrite} |
397 | % |
398 | % This writes stuff to the answers file. We make sure that it's |
399 | % appropriately protected, so that you can insert section headings and so on. |
400 | % |
401 | % \begin{macrocode} |
402 | \def\answrite#1{% |
403 | \if@filesw% |
404 | \begingroup% |
405 | \let\protect\@unexpandable@protect% |
406 | \immediate\write\ex@ansfile{#1}% |
407 | \endgroup% |
408 | \fi% |
409 | } |
410 | % \end{macrocode} |
411 | % \end{macro} |
412 | % |
413 | % \begin{macro}{\answer} |
414 | % |
415 | % The |\answer| macro needs to read until the end of the enclosing |
416 | % \env{exercise} environment (or whatever). |
417 | % |
418 | % \begin{macrocode} |
419 | \def\answer{\sv@readenv\ex@answer} |
420 | % \end{macrocode} |
421 | % |
422 | % Now for the main guts. |
423 | % |
424 | % \begin{macrocode} |
425 | \def\ex@answer#1#2{% |
426 | \begingroup% |
427 | \@bsphack% |
428 | % \end{macrocode} |
429 | % |
430 | % First of all, check to see whether any counters have changed. |
431 | % |
432 | % \begin{macrocode} |
433 | \ex@ctrcheck% |
434 | % \end{macrocode} |
435 | % |
436 | % Start a \env{doanswer} environment in the file. |
437 | % |
438 | % \begin{macrocode} |
439 | \answrite{\noexpand\begin{doanswer}{\theexercise}}% |
440 | % \end{macrocode} |
441 | % |
442 | % Set catcodes to be strange, and read lines one-at-a-time, writing them to |
443 | % the file. When finished, continue at |\ex@endanswer|. |
444 | % |
445 | % \begin{macrocode} |
446 | \let\do\@makeother\dospecials% |
447 | \sv@safespc% |
448 | \sv@read{#1}\answrite{\ex@endanswer#2}% |
449 | } |
450 | % \end{macrocode} |
451 | % |
452 | % When that's done, we wind up here. |
453 | % |
454 | % \begin{macrocode} |
455 | \def\ex@endanswer{% |
456 | \@esphack% |
457 | \answrite{\noexpand\end{doanswer}}% |
458 | \endgroup% |
459 | } |
460 | % \end{macrocode} |
461 | % \end{macro} |
462 | % |
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463 | % \begin{macro}{\skipanswer} |
464 | % |
465 | % This is much simpler. |
466 | % |
467 | % \begin{macrocode} |
468 | \let\skipanswer\ignore |
469 | % \end{macrocode} |
470 | % \end{macro} |
471 | % |
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472 | % \begin{macro}{\answers} |
473 | % |
474 | % The |\answers| macro closes the file, makes sure that future |
475 | % \env{exercise}s with answers cause an error, and reads in the file. |
476 | % |
477 | % \begin{macrocode} |
478 | \def\answers{% |
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479 | \@ifnextchar[{\answers@i\input}{\answers@i\@input[\ex@ansfilename]}% |
480 | } |
481 | \def\answers@i#1[#2]{% |
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482 | \immediate\closeout\ex@ansfile% |
483 | \global\let\answrite\exerr@toolate% |
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484 | \ex@withext{#1}{#2}{ans}% |
485 | } |
486 | \def\q@delim{\q@delim} |
487 | \def\ex@withext#1#2#3{% |
488 | \edef\next@##1{\noexpand\ex@ext@i{##1}{#2}{#3}#2.\noexpand\q@delim}% |
489 | \next@{#1}% |
490 | } |
491 | \def\ex@ext@i#1#2#3#4.#5\q@delim{% |
492 | \ifx\q@delim#5\q@delim\def\next@{#1{#2.#3}}% |
493 | \else\def\next@{#1{#2}}\fi% |
494 | \next@% |
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495 | } |
496 | % \end{macrocode} |
497 | % \end{macro} |
498 | % |
499 | % \begin{environment}{doanswer} |
500 | % |
501 | % A very simple environment. We set the exercise number in bold and then |
502 | % just write the text. |
503 | % |
504 | % \begin{macrocode} |
505 | \def\doanswer#1{% |
506 | \exfix% |
507 | \trivlist\advance\itemindent\labelsep% |
508 | \item[\textbf{#1}]% |
509 | } |
510 | \let\enddoanswer\endtrivlist |
511 | % \end{macrocode} |
512 | % \end{environment} |
513 | % |
514 | % \subsection{Lists inside paragraphs} |
515 | % |
516 | % \begin{environment}{parlist} |
517 | % |
518 | % The \env{parlist} environment is a trimmed-down version of a normal list. |
519 | % We todge the |\item| command, make |\list| and |\trivlist| make errors, and |
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520 | % do various normal list things. |
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521 | % |
522 | % \begin{macrocode} |
523 | \def\parlist#1#2{% |
524 | \let\@trivlist\exerr@parlist% |
525 | \def\@itemlabel{#1}% |
526 | \let\makelabel\relax% |
527 | \@nmbrlistfalse% |
528 | #2% |
529 | \let\item\pl@item% |
530 | \ignorespaces% |
531 | } |
532 | % \end{macrocode} |
533 | % \end{environment} |
534 | % |
535 | % \begin{macro}{\pl@item} |
536 | % |
537 | % This is the implementation of |\item| within a \env{parlist}. The main |
538 | % interesting point is the game with boxes, which has the objective of |
539 | % extracting the text of the item, together with any style changes set by |
540 | % |\makelabel|, but without any stupid bits of glue, or |\llap| or anything |
541 | % like that. |
542 | % |
543 | % \begin{macrocode} |
544 | \def\pl@item{\@ifnextchar[\pl@item@i{\pl@item@i[\@itemlabel]}} |
545 | \def\pl@item@i[#1]{% |
546 | \if@nmbrlist\refstepcounter{\@listctr}\fi% |
547 | \setbox\z@\hbox{\makelabel{\global\setbox\@ne\hbox{#1}}}% |
548 | \ifvmode\leavevmode\else\unskip\hskip1em\fi\box\@ne~\ignorespaces% |
549 | } |
550 | % \end{macrocode} |
551 | % \end{macro} |
552 | % |
553 | % \begin{macro}{\useparlist} |
554 | % |
555 | % We just set the \env{list} environment to use \env{parlist}. |
556 | % |
557 | % \begin{macrocode} |
558 | \def\useparlist{\let\list\parlist\let\endlist\relax} |
559 | % \end{macrocode} |
560 | % \end{macro} |
561 | % |
562 | % \begin{environment}{parenum} |
563 | % |
564 | % Very simple, this. Note that we don't run |\endenumerate|, because that's |
565 | % |\let| to |\endlist|. |
566 | % |
567 | % \begin{macrocode} |
568 | \def\parenum{\useparlist\enumerate} |
569 | \let\endparenum\endparlist |
570 | % \end{macrocode} |
571 | % \end{environment} |
572 | % |
573 | % \subsection{Errors} |
574 | % |
575 | % \begin{macrocode} |
576 | \def\exerr@toolate{% |
577 | \PackageError{exercise}{Too late now for \string\answrite}{% |
578 | You can't write answers after you've read the file in. I've^^J% |
579 | ignored the text you attempted to write. This is why answers^^J% |
580 | go at the end of a book!% |
581 | }% |
582 | } |
583 | \def\exerr@parlist{% |
584 | \PackageError{exercise}{You can't nest a `list' inside a `parlist'.}{% |
585 | I've found a `list' or `trivlist' environment nested inside^^J% |
db127fce |
586 | a `parlist'. This isn't allowed. You're probably doomed now.% |
86f6a31e |
587 | }% |
588 | } |
589 | %</package> |
590 | % \end{macrocode} |
591 | % |
592 | % Done. |
593 | % |
594 | % \hfill Mark Wooding, \today |
595 | % |
596 | % \Finale |
597 | % |
598 | \endinput |