2 * Copyright (c) 1989, 1993
3 * The Regents of the University of California. All rights reserved.
5 * This code is derived from software contributed to Berkeley by
6 * Eamonn McManus of Trinity College Dublin.
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
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.
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
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 $
39 * $DragonFly: src/games/arithmetic/arithmetic.c,v 1.3 2003/11/12 14:53:52 eirikn Exp $
43 * By Eamonn McManus, Trinity College Dublin <emcmanus@cs.tcd.ie>.
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:
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.
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.
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.
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
70 #include <sys/types.h>
71 #include <sys/signal.h>
79 const char keylist[] = "+-x/";
80 const char defaultkeys[] = "+-";
81 const char *keys = defaultkeys;
82 int nkeys = sizeof(defaultkeys) - 1;
88 static void usage (void);
89 int getrandom (int, int, int);
92 void penalise (int, int, int);
94 void showstats (void);
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.
110 /* Revoke setgid privileges */
113 while ((ch = getopt(argc, argv, "r:o:")) != -1)
118 for (p = keys = optarg; *p; ++p)
119 if (!index(keylist, *p)) {
120 (void)fprintf(stderr,
121 "arithmetic: unknown key.\n");
128 if ((rangemax = atoi(optarg)) <= 0) {
129 (void)fprintf(stderr,
130 "arithmetic: invalid range.\n");
141 /* Seed the random-number generator. */
144 (void)signal(SIGINT, intr);
146 /* Now ask the questions. */
148 for (cnt = NQUESTS; cnt--;)
149 if (problem() == EOF)
156 /* Handle interrupt character. Print score and exit. */
165 /* Print score. Original `arithmetic' had a delay after printing it. */
169 if (nright + nwrong > 0) {
170 (void)printf("\n\nRights %d; Wrongs %d; Score %d%%",
171 nright, nwrong, (int)(100L * nright / (nright + nwrong)));
173 (void)printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n",
174 (long)qtime, (float)qtime / nright);
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.
191 time_t start, finish;
192 int left, op, right, result;
198 op = keys[random() % nkeys];
200 right = getrandom(rangemax + 1, op, 1);
202 /* Get the operands. */
205 left = getrandom(rangemax + 1, op, 0);
206 result = left + right;
209 result = getrandom(rangemax + 1, op, 0);
210 left = right + result;
213 left = getrandom(rangemax + 1, op, 0);
214 result = left * right;
217 right = getrandom(rangemax, op, 1) + 1;
218 result = getrandom(rangemax + 1, op, 0);
219 left = right * result + random() % right;
224 * A very big maxrange could cause negative values to pop
225 * up, owing to overflow.
227 if (result < 0 || left < 0)
230 (void)printf("%d %c %d = ", left, op, right);
231 (void)fflush(stdout);
235 * Keep looping until the correct answer is given, or until EOF or
236 * interrupt is typed.
239 if (!fgets(line, sizeof(line), stdin)) {
243 for (p = line; *p && isspace(*p); ++p);
245 (void)printf("Please type a number.\n");
248 if (atoi(p) == result) {
249 (void)printf("Right!\n");
253 /* Wrong answer; penalise and ask again. */
254 (void)printf("What?\n");
256 penalise(right, op, 1);
257 if (op == 'x' || op == '+')
258 penalise(left, op, 0);
260 penalise(result, op, 0);
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
271 qtime += finish - start;
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.
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.
289 int penalty[sizeof(keylist) - 1][2];
291 int value, penalty; /* Penalised value and its penalty. */
292 struct penalty *next;
293 } *penlist[sizeof(keylist) - 1][2];
295 #define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */
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?).
303 penalise(value, op, operand)
304 int value, op, operand;
309 if ((p = (struct penalty *)malloc((u_int)sizeof(*p))) == NULL)
311 p->next = penlist[op][operand];
312 penlist[op][operand] = p;
313 penalty[op][operand] += p->penalty = WRONGPENALTY;
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.
324 getrandom(maxval, op, operand)
325 int maxval, op, operand;
328 struct penalty **pp, *p;
331 value = random() % (maxval + penalty[op][operand]);
334 * 0 to maxval - 1 is a number to be used directly; bigger values
335 * are positions to be located in the penalty list.
342 * Find the penalty at position `value'; decrement its penalty and
343 * delete it if it reaches 0; return the corresponding value.
345 for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) {
346 if (p->penalty > value) {
348 penalty[op][operand]--;
349 if (--(p->penalty) <= 0) {
351 (void)free((char *)*pp);
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
363 (void)fprintf(stderr, "arithmetic: bug: inconsistent penalties\n");
368 /* Return an index for the character op, which is one of [+-x/]. */
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);
383 /* Print usage message and quit. */
387 (void)fprintf(stderr, "usage: arithmetic [-o +-x/] [-r range]\n");