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[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 $
e12c1abe 39 * $DragonFly: src/games/arithmetic/arithmetic.c,v 1.4 2005/04/24 15:31:30 liamfoy 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
851dc90d
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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
e12c1abe 104main(int argc, char **argv)
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105{
106 int ch, cnt;
107
108 /* Revoke setgid privileges */
109 setgid(getgid());
110
111 while ((ch = getopt(argc, argv, "r:o:")) != -1)
112 switch(ch) {
113 case 'o': {
114 const char *p;
115
116 for (p = keys = optarg; *p; ++p)
117 if (!index(keylist, *p)) {
118 (void)fprintf(stderr,
119 "arithmetic: unknown key.\n");
120 exit(1);
121 }
122 nkeys = p - optarg;
123 break;
124 }
125 case 'r':
126 if ((rangemax = atoi(optarg)) <= 0) {
127 (void)fprintf(stderr,
128 "arithmetic: invalid range.\n");
129 exit(1);
130 }
131 break;
132 case '?':
133 default:
134 usage();
135 }
136 if (argc -= optind)
137 usage();
138
139 /* Seed the random-number generator. */
140 srandomdev();
141
142 (void)signal(SIGINT, intr);
143
144 /* Now ask the questions. */
145 for (;;) {
146 for (cnt = NQUESTS; cnt--;)
147 if (problem() == EOF)
148 exit(0);
149 showstats();
150 }
151 /* NOTREACHED */
152}
153
154/* Handle interrupt character. Print score and exit. */
155void
e12c1abe 156intr(__unused int sig)
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157{
158 showstats();
159 exit(0);
160}
161
162/* Print score. Original `arithmetic' had a delay after printing it. */
163void
e12c1abe 164showstats(void)
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165{
166 if (nright + nwrong > 0) {
167 (void)printf("\n\nRights %d; Wrongs %d; Score %d%%",
168 nright, nwrong, (int)(100L * nright / (nright + nwrong)));
169 if (nright > 0)
170 (void)printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n",
171 (long)qtime, (float)qtime / nright);
172 }
173 (void)printf("\n");
174}
175
176/*
177 * Pick a problem and ask it. Keeps asking the same problem until supplied
178 * with the correct answer, or until EOF or interrupt is typed. Problems are
179 * selected such that the right operand and either the left operand (for +, x)
180 * or the correct result (for -, /) are in the range 0 to rangemax. Each wrong
181 * answer causes the numbers in the problem to be penalised, so that they are
182 * more likely to appear in subsequent problems.
183 */
184int
e12c1abe 185problem(void)
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186{
187 char *p;
188 time_t start, finish;
189 int left, op, right, result;
190 char line[80];
191
192 left = 0;
193 right = 0;
194 result = 0;
195 op = keys[random() % nkeys];
196 if (op != '/')
197 right = getrandom(rangemax + 1, op, 1);
198retry:
199 /* Get the operands. */
200 switch (op) {
201 case '+':
202 left = getrandom(rangemax + 1, op, 0);
203 result = left + right;
204 break;
205 case '-':
206 result = getrandom(rangemax + 1, op, 0);
207 left = right + result;
208 break;
209 case 'x':
210 left = getrandom(rangemax + 1, op, 0);
211 result = left * right;
212 break;
213 case '/':
214 right = getrandom(rangemax, op, 1) + 1;
215 result = getrandom(rangemax + 1, op, 0);
216 left = right * result + random() % right;
217 break;
218 }
219
220 /*
221 * A very big maxrange could cause negative values to pop
222 * up, owing to overflow.
223 */
224 if (result < 0 || left < 0)
225 goto retry;
226
227 (void)printf("%d %c %d = ", left, op, right);
228 (void)fflush(stdout);
229 (void)time(&start);
230
231 /*
232 * Keep looping until the correct answer is given, or until EOF or
233 * interrupt is typed.
234 */
235 for (;;) {
236 if (!fgets(line, sizeof(line), stdin)) {
237 (void)printf("\n");
238 return(EOF);
239 }
240 for (p = line; *p && isspace(*p); ++p);
241 if (!isdigit(*p)) {
242 (void)printf("Please type a number.\n");
243 continue;
244 }
245 if (atoi(p) == result) {
246 (void)printf("Right!\n");
247 ++nright;
248 break;
249 }
250 /* Wrong answer; penalise and ask again. */
251 (void)printf("What?\n");
252 ++nwrong;
253 penalise(right, op, 1);
254 if (op == 'x' || op == '+')
255 penalise(left, op, 0);
256 else
257 penalise(result, op, 0);
258 }
259
260 /*
261 * Accumulate the time taken. Obviously rounding errors happen here;
262 * however they should cancel out, because some of the time you are
263 * charged for a partially elapsed second at the start, and some of
264 * the time you are not charged for a partially elapsed second at the
265 * end.
266 */
267 (void)time(&finish);
268 qtime += finish - start;
269 return(0);
270}
271
272/*
273 * Here is the code for accumulating penalties against the numbers for which
274 * a wrong answer was given. The right operand and either the left operand
275 * (for +, x) or the result (for -, /) are stored in a list for the particular
276 * operation, and each becomes more likely to appear again in that operation.
277 * Initially, each number is charged a penalty of WRONGPENALTY, giving it that
278 * many extra chances of appearing. Each time it is selected because of this,
279 * its penalty is decreased by one; it is removed when it reaches 0.
280 *
281 * The penalty[] array gives the sum of all penalties in the list for
282 * each operation and each operand. The penlist[] array has the lists of
283 * penalties themselves.
284 */
285
286int penalty[sizeof(keylist) - 1][2];
287struct penalty {
288 int value, penalty; /* Penalised value and its penalty. */
289 struct penalty *next;
290} *penlist[sizeof(keylist) - 1][2];
291
292#define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */
293
294/*
295 * Add a penalty for the number `value' to the list for operation `op',
296 * operand number `operand' (0 or 1). If we run out of memory, we just
297 * forget about the penalty (how likely is this, anyway?).
298 */
299void
e12c1abe 300penalise(int value, int op, int operand)
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301{
302 struct penalty *p;
303
304 op = opnum(op);
305 if ((p = (struct penalty *)malloc((u_int)sizeof(*p))) == NULL)
306 return;
307 p->next = penlist[op][operand];
308 penlist[op][operand] = p;
309 penalty[op][operand] += p->penalty = WRONGPENALTY;
310 p->value = value;
311}
312
313/*
314 * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1)
315 * of operation `op'. The random number we generate is either used directly
316 * as a value, or represents a position in the penalty list. If the latter,
317 * we find the corresponding value and return that, decreasing its penalty.
318 */
319int
e12c1abe 320getrandom(int maxval, int op, int operand)
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321{
322 int value;
323 struct penalty **pp, *p;
324
325 op = opnum(op);
326 value = random() % (maxval + penalty[op][operand]);
327
328 /*
329 * 0 to maxval - 1 is a number to be used directly; bigger values
330 * are positions to be located in the penalty list.
331 */
332 if (value < maxval)
333 return(value);
334 value -= maxval;
335
336 /*
337 * Find the penalty at position `value'; decrement its penalty and
338 * delete it if it reaches 0; return the corresponding value.
339 */
340 for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) {
341 if (p->penalty > value) {
342 value = p->value;
343 penalty[op][operand]--;
344 if (--(p->penalty) <= 0) {
345 p = p->next;
346 (void)free((char *)*pp);
347 *pp = p;
348 }
349 return(value);
350 }
351 value -= p->penalty;
352 }
353 /*
354 * We can only get here if the value from the penalty[] array doesn't
355 * correspond to the actual sum of penalties in the list. Provide an
356 * obscure message.
357 */
358 (void)fprintf(stderr, "arithmetic: bug: inconsistent penalties\n");
359 exit(1);
360 /* NOTREACHED */
361}
362
363/* Return an index for the character op, which is one of [+-x/]. */
364int
e12c1abe 365opnum(int op)
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366{
367 char *p;
368
369 if (op == 0 || (p = index(keylist, op)) == NULL) {
370 (void)fprintf(stderr,
371 "arithmetic: bug: op %c not in keylist %s\n", op, keylist);
372 exit(1);
373 }
374 return(p - keylist);
375}
376
377/* Print usage message and quit. */
378static void
e12c1abe 379usage(void)
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380{
381 (void)fprintf(stderr, "usage: arithmetic [-o +-x/] [-r range]\n");
382 exit(1);
383}