- Add further functionality to check for invalid characters
[dragonfly.git] / games / arithmetic / arithmetic.c
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1/*
2 * Copyright (c) 1989, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Eamonn McManus of Trinity College Dublin.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. All advertising materials mentioning features or use of this software
17 * must display the following acknowledgement:
18 * This product includes software developed by the University of
19 * California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
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35 *
36 * @(#) Copyright (c) 1989, 1993 The Regents of the University of California. All rights reserved.
37 * @(#)arithmetic.c 8.1 (Berkeley) 5/31/93
38 * $FreeBSD: src/games/arithmetic/arithmetic.c,v 1.10 1999/12/12 06:40:28 billf Exp $
851dc90d 39 * $DragonFly: src/games/arithmetic/arithmetic.c,v 1.3 2003/11/12 14:53:52 eirikn Exp $
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40 */
41
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42/*
43 * By Eamonn McManus, Trinity College Dublin <emcmanus@cs.tcd.ie>.
44 *
45 * The operation of this program mimics that of the standard Unix game
46 * `arithmetic'. I've made it as close as I could manage without examining
47 * the source code. The principal differences are:
48 *
49 * The method of biasing towards numbers that had wrong answers in the past
50 * is different; original `arithmetic' seems to retain the bias forever,
51 * whereas this program lets the bias gradually decay as it is used.
52 *
53 * Original `arithmetic' delays for some period (3 seconds?) after printing
54 * the score. I saw no reason for this delay, so I scrapped it.
55 *
56 * There is no longer a limitation on the maximum range that can be supplied
57 * to the program. The original program required it to be less than 100.
58 * Anomalous results may occur with this program if ranges big enough to
59 * allow overflow are given.
60 *
61 * I have obviously not attempted to duplicate bugs in the original. It
62 * would go into an infinite loop if invoked as `arithmetic / 0'. It also
63 * did not recognise an EOF in its input, and would continue trying to read
64 * after it. It did not check that the input was a valid number, treating any
65 * garbage as 0. Finally, it did not flush stdout after printing its prompt,
66 * so in the unlikely event that stdout was not a terminal, it would not work
67 * properly.
68 */
69
70#include <sys/types.h>
71#include <sys/signal.h>
72#include <ctype.h>
73#include <stdio.h>
74#include <string.h>
75#include <stdlib.h>
76#include <time.h>
77#include <unistd.h>
78
79const char keylist[] = "+-x/";
80const char defaultkeys[] = "+-";
81const char *keys = defaultkeys;
82int nkeys = sizeof(defaultkeys) - 1;
83int rangemax = 10;
84int nright, nwrong;
85time_t qtime;
86#define NQUESTS 20
87
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88static void usage (void);
89int getrandom (int, int, int);
90void intr (int);
91int opnum (int);
92void penalise (int, int, int);
93int problem (void);
94void showstats (void);
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95
96/*
97 * Select keys from +-x/ to be asked addition, subtraction, multiplication,
98 * and division problems. More than one key may be given. The default is
99 * +-. Specify a range to confine the operands to 0 - range. Default upper
100 * bound is 10. After every NQUESTS questions, statistics on the performance
101 * so far are printed.
102 */
103int
104main(argc, argv)
105 int argc;
106 char **argv;
107{
108 int ch, cnt;
109
110 /* Revoke setgid privileges */
111 setgid(getgid());
112
113 while ((ch = getopt(argc, argv, "r:o:")) != -1)
114 switch(ch) {
115 case 'o': {
116 const char *p;
117
118 for (p = keys = optarg; *p; ++p)
119 if (!index(keylist, *p)) {
120 (void)fprintf(stderr,
121 "arithmetic: unknown key.\n");
122 exit(1);
123 }
124 nkeys = p - optarg;
125 break;
126 }
127 case 'r':
128 if ((rangemax = atoi(optarg)) <= 0) {
129 (void)fprintf(stderr,
130 "arithmetic: invalid range.\n");
131 exit(1);
132 }
133 break;
134 case '?':
135 default:
136 usage();
137 }
138 if (argc -= optind)
139 usage();
140
141 /* Seed the random-number generator. */
142 srandomdev();
143
144 (void)signal(SIGINT, intr);
145
146 /* Now ask the questions. */
147 for (;;) {
148 for (cnt = NQUESTS; cnt--;)
149 if (problem() == EOF)
150 exit(0);
151 showstats();
152 }
153 /* NOTREACHED */
154}
155
156/* Handle interrupt character. Print score and exit. */
157void
158intr(sig)
159 int sig;
160{
161 showstats();
162 exit(0);
163}
164
165/* Print score. Original `arithmetic' had a delay after printing it. */
166void
167showstats()
168{
169 if (nright + nwrong > 0) {
170 (void)printf("\n\nRights %d; Wrongs %d; Score %d%%",
171 nright, nwrong, (int)(100L * nright / (nright + nwrong)));
172 if (nright > 0)
173 (void)printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n",
174 (long)qtime, (float)qtime / nright);
175 }
176 (void)printf("\n");
177}
178
179/*
180 * Pick a problem and ask it. Keeps asking the same problem until supplied
181 * with the correct answer, or until EOF or interrupt is typed. Problems are
182 * selected such that the right operand and either the left operand (for +, x)
183 * or the correct result (for -, /) are in the range 0 to rangemax. Each wrong
184 * answer causes the numbers in the problem to be penalised, so that they are
185 * more likely to appear in subsequent problems.
186 */
187int
188problem()
189{
190 char *p;
191 time_t start, finish;
192 int left, op, right, result;
193 char line[80];
194
195 left = 0;
196 right = 0;
197 result = 0;
198 op = keys[random() % nkeys];
199 if (op != '/')
200 right = getrandom(rangemax + 1, op, 1);
201retry:
202 /* Get the operands. */
203 switch (op) {
204 case '+':
205 left = getrandom(rangemax + 1, op, 0);
206 result = left + right;
207 break;
208 case '-':
209 result = getrandom(rangemax + 1, op, 0);
210 left = right + result;
211 break;
212 case 'x':
213 left = getrandom(rangemax + 1, op, 0);
214 result = left * right;
215 break;
216 case '/':
217 right = getrandom(rangemax, op, 1) + 1;
218 result = getrandom(rangemax + 1, op, 0);
219 left = right * result + random() % right;
220 break;
221 }
222
223 /*
224 * A very big maxrange could cause negative values to pop
225 * up, owing to overflow.
226 */
227 if (result < 0 || left < 0)
228 goto retry;
229
230 (void)printf("%d %c %d = ", left, op, right);
231 (void)fflush(stdout);
232 (void)time(&start);
233
234 /*
235 * Keep looping until the correct answer is given, or until EOF or
236 * interrupt is typed.
237 */
238 for (;;) {
239 if (!fgets(line, sizeof(line), stdin)) {
240 (void)printf("\n");
241 return(EOF);
242 }
243 for (p = line; *p && isspace(*p); ++p);
244 if (!isdigit(*p)) {
245 (void)printf("Please type a number.\n");
246 continue;
247 }
248 if (atoi(p) == result) {
249 (void)printf("Right!\n");
250 ++nright;
251 break;
252 }
253 /* Wrong answer; penalise and ask again. */
254 (void)printf("What?\n");
255 ++nwrong;
256 penalise(right, op, 1);
257 if (op == 'x' || op == '+')
258 penalise(left, op, 0);
259 else
260 penalise(result, op, 0);
261 }
262
263 /*
264 * Accumulate the time taken. Obviously rounding errors happen here;
265 * however they should cancel out, because some of the time you are
266 * charged for a partially elapsed second at the start, and some of
267 * the time you are not charged for a partially elapsed second at the
268 * end.
269 */
270 (void)time(&finish);
271 qtime += finish - start;
272 return(0);
273}
274
275/*
276 * Here is the code for accumulating penalties against the numbers for which
277 * a wrong answer was given. The right operand and either the left operand
278 * (for +, x) or the result (for -, /) are stored in a list for the particular
279 * operation, and each becomes more likely to appear again in that operation.
280 * Initially, each number is charged a penalty of WRONGPENALTY, giving it that
281 * many extra chances of appearing. Each time it is selected because of this,
282 * its penalty is decreased by one; it is removed when it reaches 0.
283 *
284 * The penalty[] array gives the sum of all penalties in the list for
285 * each operation and each operand. The penlist[] array has the lists of
286 * penalties themselves.
287 */
288
289int penalty[sizeof(keylist) - 1][2];
290struct penalty {
291 int value, penalty; /* Penalised value and its penalty. */
292 struct penalty *next;
293} *penlist[sizeof(keylist) - 1][2];
294
295#define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */
296
297/*
298 * Add a penalty for the number `value' to the list for operation `op',
299 * operand number `operand' (0 or 1). If we run out of memory, we just
300 * forget about the penalty (how likely is this, anyway?).
301 */
302void
303penalise(value, op, operand)
304 int value, op, operand;
305{
306 struct penalty *p;
307
308 op = opnum(op);
309 if ((p = (struct penalty *)malloc((u_int)sizeof(*p))) == NULL)
310 return;
311 p->next = penlist[op][operand];
312 penlist[op][operand] = p;
313 penalty[op][operand] += p->penalty = WRONGPENALTY;
314 p->value = value;
315}
316
317/*
318 * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1)
319 * of operation `op'. The random number we generate is either used directly
320 * as a value, or represents a position in the penalty list. If the latter,
321 * we find the corresponding value and return that, decreasing its penalty.
322 */
323int
324getrandom(maxval, op, operand)
325 int maxval, op, operand;
326{
327 int value;
328 struct penalty **pp, *p;
329
330 op = opnum(op);
331 value = random() % (maxval + penalty[op][operand]);
332
333 /*
334 * 0 to maxval - 1 is a number to be used directly; bigger values
335 * are positions to be located in the penalty list.
336 */
337 if (value < maxval)
338 return(value);
339 value -= maxval;
340
341 /*
342 * Find the penalty at position `value'; decrement its penalty and
343 * delete it if it reaches 0; return the corresponding value.
344 */
345 for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) {
346 if (p->penalty > value) {
347 value = p->value;
348 penalty[op][operand]--;
349 if (--(p->penalty) <= 0) {
350 p = p->next;
351 (void)free((char *)*pp);
352 *pp = p;
353 }
354 return(value);
355 }
356 value -= p->penalty;
357 }
358 /*
359 * We can only get here if the value from the penalty[] array doesn't
360 * correspond to the actual sum of penalties in the list. Provide an
361 * obscure message.
362 */
363 (void)fprintf(stderr, "arithmetic: bug: inconsistent penalties\n");
364 exit(1);
365 /* NOTREACHED */
366}
367
368/* Return an index for the character op, which is one of [+-x/]. */
369int
370opnum(op)
371 int op;
372{
373 char *p;
374
375 if (op == 0 || (p = index(keylist, op)) == NULL) {
376 (void)fprintf(stderr,
377 "arithmetic: bug: op %c not in keylist %s\n", op, keylist);
378 exit(1);
379 }
380 return(p - keylist);
381}
382
383/* Print usage message and quit. */
384static void
385usage()
386{
387 (void)fprintf(stderr, "usage: arithmetic [-o +-x/] [-r range]\n");
388 exit(1);
389}