Annotation of src/games/arithmetic/arithmetic.c, Revision 1.21.16.1
1.21.16.1! matt 1: /* $NetBSD$ */
1.5 cgd 2:
1.1 cgd 3: /*
1.5 cgd 4: * Copyright (c) 1989, 1993
5: * The Regents of the University of California. All rights reserved.
1.1 cgd 6: *
7: * This code is derived from software contributed to Berkeley by
8: * Eamonn McManus of Trinity College Dublin.
9: *
10: * Redistribution and use in source and binary forms, with or without
11: * modification, are permitted provided that the following conditions
12: * are met:
13: * 1. Redistributions of source code must retain the above copyright
14: * notice, this list of conditions and the following disclaimer.
15: * 2. Redistributions in binary form must reproduce the above copyright
16: * notice, this list of conditions and the following disclaimer in the
17: * documentation and/or other materials provided with the distribution.
1.19 agc 18: * 3. Neither the name of the University nor the names of its contributors
1.1 cgd 19: * may be used to endorse or promote products derived from this software
20: * without specific prior written permission.
21: *
22: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32: * SUCH DAMAGE.
33: */
34:
1.7 lukem 35: #include <sys/cdefs.h>
1.1 cgd 36: #ifndef lint
1.7 lukem 37: __COPYRIGHT("@(#) Copyright (c) 1989, 1993\n\
38: The Regents of the University of California. All rights reserved.\n");
1.1 cgd 39: #endif /* not lint */
40:
41: #ifndef lint
1.5 cgd 42: #if 0
43: static char sccsid[] = "@(#)arithmetic.c 8.1 (Berkeley) 5/31/93";
44: #else
1.21.16.1! matt 45: __RCSID("$NetBSD$");
1.5 cgd 46: #endif
1.1 cgd 47: #endif /* not lint */
48:
49: /*
50: * By Eamonn McManus, Trinity College Dublin <emcmanus@cs.tcd.ie>.
51: *
52: * The operation of this program mimics that of the standard Unix game
53: * `arithmetic'. I've made it as close as I could manage without examining
54: * the source code. The principal differences are:
55: *
56: * The method of biasing towards numbers that had wrong answers in the past
57: * is different; original `arithmetic' seems to retain the bias forever,
58: * whereas this program lets the bias gradually decay as it is used.
59: *
60: * Original `arithmetic' delays for some period (3 seconds?) after printing
61: * the score. I saw no reason for this delay, so I scrapped it.
62: *
63: * There is no longer a limitation on the maximum range that can be supplied
64: * to the program. The original program required it to be less than 100.
65: * Anomalous results may occur with this program if ranges big enough to
66: * allow overflow are given.
67: *
68: * I have obviously not attempted to duplicate bugs in the original. It
69: * would go into an infinite loop if invoked as `arithmetic / 0'. It also
70: * did not recognise an EOF in its input, and would continue trying to read
71: * after it. It did not check that the input was a valid number, treating any
72: * garbage as 0. Finally, it did not flush stdout after printing its prompt,
73: * so in the unlikely event that stdout was not a terminal, it would not work
74: * properly.
75: */
76:
77: #include <sys/types.h>
1.7 lukem 78: #include <err.h>
79: #include <ctype.h>
1.4 jtc 80: #include <signal.h>
1.1 cgd 81: #include <stdio.h>
1.7 lukem 82: #include <stdlib.h>
1.1 cgd 83: #include <string.h>
1.2 mycroft 84: #include <time.h>
1.10 perry 85: #include <unistd.h>
1.1 cgd 86:
1.20 jsm 87: int getrandom(int, int, int);
1.21.16.1! matt 88: void intr(int) __dead;
1.20 jsm 89: int main(int, char *[]);
90: int opnum(int);
91: void penalise(int, int, int);
92: int problem(void);
93: void showstats(int);
1.21.16.1! matt 94: void usage(void) __dead;
1.7 lukem 95:
1.12 hubertf 96: const char keylist[] = "+-x/";
97: const char defaultkeys[] = "+-";
98: const char *keys = defaultkeys;
1.1 cgd 99: int nkeys = sizeof(defaultkeys) - 1;
100: int rangemax = 10;
101: int nright, nwrong;
102: time_t qtime;
103: #define NQUESTS 20
104:
105: /*
106: * Select keys from +-x/ to be asked addition, subtraction, multiplication,
107: * and division problems. More than one key may be given. The default is
108: * +-. Specify a range to confine the operands to 0 - range. Default upper
109: * bound is 10. After every NQUESTS questions, statistics on the performance
110: * so far are printed.
111: */
1.6 jtc 112: int
1.1 cgd 113: main(argc, argv)
114: int argc;
115: char **argv;
116: {
117: int ch, cnt;
118:
1.13 hubertf 119: /* Revoke setgid privileges */
1.15 mycroft 120: setgid(getgid());
1.13 hubertf 121:
1.8 lukem 122: while ((ch = getopt(argc, argv, "r:o:")) != -1)
1.1 cgd 123: switch(ch) {
124: case 'o': {
1.12 hubertf 125: const char *p;
1.1 cgd 126:
127: for (p = keys = optarg; *p; ++p)
1.7 lukem 128: if (!strchr(keylist, *p))
129: errx(1, "arithmetic: unknown key.");
1.1 cgd 130: nkeys = p - optarg;
131: break;
132: }
133: case 'r':
1.7 lukem 134: if ((rangemax = atoi(optarg)) <= 0)
135: errx(1, "arithmetic: invalid range.");
1.1 cgd 136: break;
137: case '?':
138: default:
139: usage();
140: }
141: if (argc -= optind)
142: usage();
143:
144: /* Seed the random-number generator. */
145: srandom((int)time((time_t *)NULL));
146:
147: (void)signal(SIGINT, intr);
148:
149: /* Now ask the questions. */
150: for (;;) {
151: for (cnt = NQUESTS; cnt--;)
152: if (problem() == EOF)
153: exit(0);
1.18 hubertf 154: showstats(0);
1.1 cgd 155: }
156: /* NOTREACHED */
157: }
158:
159: /* Handle interrupt character. Print score and exit. */
160: void
1.7 lukem 161: intr(dummy)
1.21.16.1! matt 162: int dummy __unused;
1.1 cgd 163: {
1.18 hubertf 164: showstats(1);
1.1 cgd 165: exit(0);
166: }
167:
168: /* Print score. Original `arithmetic' had a delay after printing it. */
1.7 lukem 169: void
1.18 hubertf 170: showstats(bool_sigint)
171: int bool_sigint;
1.1 cgd 172: {
173: if (nright + nwrong > 0) {
174: (void)printf("\n\nRights %d; Wrongs %d; Score %d%%",
175: nright, nwrong, (int)(100L * nright / (nright + nwrong)));
176: if (nright > 0)
177: (void)printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n",
178: (long)qtime, (float)qtime / nright);
1.18 hubertf 179: }
180: if(!bool_sigint) {
181: (void)printf("Press RETURN to continue...\n");
182: while(!getchar()) ;
1.1 cgd 183: }
184: (void)printf("\n");
185: }
186:
187: /*
188: * Pick a problem and ask it. Keeps asking the same problem until supplied
189: * with the correct answer, or until EOF or interrupt is typed. Problems are
190: * selected such that the right operand and either the left operand (for +, x)
191: * or the correct result (for -, /) are in the range 0 to rangemax. Each wrong
192: * answer causes the numbers in the problem to be penalised, so that they are
193: * more likely to appear in subsequent problems.
194: */
1.7 lukem 195: int
1.1 cgd 196: problem()
197: {
1.7 lukem 198: char *p;
1.1 cgd 199: time_t start, finish;
200: int left, op, right, result;
201: char line[80];
202:
1.9 is 203: right = left = result = 0;
1.1 cgd 204: op = keys[random() % nkeys];
205: if (op != '/')
206: right = getrandom(rangemax + 1, op, 1);
207: retry:
208: /* Get the operands. */
209: switch (op) {
210: case '+':
211: left = getrandom(rangemax + 1, op, 0);
212: result = left + right;
213: break;
214: case '-':
215: result = getrandom(rangemax + 1, op, 0);
216: left = right + result;
217: break;
218: case 'x':
219: left = getrandom(rangemax + 1, op, 0);
220: result = left * right;
221: break;
222: case '/':
223: right = getrandom(rangemax, op, 1) + 1;
224: result = getrandom(rangemax + 1, op, 0);
225: left = right * result + random() % right;
226: break;
227: }
228:
229: /*
230: * A very big maxrange could cause negative values to pop
231: * up, owing to overflow.
232: */
233: if (result < 0 || left < 0)
234: goto retry;
235:
236: (void)printf("%d %c %d = ", left, op, right);
237: (void)fflush(stdout);
238: (void)time(&start);
239:
240: /*
241: * Keep looping until the correct answer is given, or until EOF or
242: * interrupt is typed.
243: */
244: for (;;) {
245: if (!fgets(line, sizeof(line), stdin)) {
246: (void)printf("\n");
247: return(EOF);
248: }
1.21 dsl 249: for (p = line; *p && isspace((unsigned char)*p); ++p);
250: if (!isdigit((unsigned char)*p)) {
1.1 cgd 251: (void)printf("Please type a number.\n");
252: continue;
253: }
254: if (atoi(p) == result) {
255: (void)printf("Right!\n");
256: ++nright;
257: break;
258: }
259: /* Wrong answer; penalise and ask again. */
260: (void)printf("What?\n");
261: ++nwrong;
262: penalise(right, op, 1);
263: if (op == 'x' || op == '+')
264: penalise(left, op, 0);
265: else
266: penalise(result, op, 0);
267: }
268:
269: /*
270: * Accumulate the time taken. Obviously rounding errors happen here;
271: * however they should cancel out, because some of the time you are
272: * charged for a partially elapsed second at the start, and some of
273: * the time you are not charged for a partially elapsed second at the
274: * end.
275: */
276: (void)time(&finish);
277: qtime += finish - start;
278: return(0);
279: }
280:
281: /*
282: * Here is the code for accumulating penalties against the numbers for which
283: * a wrong answer was given. The right operand and either the left operand
284: * (for +, x) or the result (for -, /) are stored in a list for the particular
285: * operation, and each becomes more likely to appear again in that operation.
286: * Initially, each number is charged a penalty of WRONGPENALTY, giving it that
287: * many extra chances of appearing. Each time it is selected because of this,
288: * its penalty is decreased by one; it is removed when it reaches 0.
289: *
290: * The penalty[] array gives the sum of all penalties in the list for
291: * each operation and each operand. The penlist[] array has the lists of
292: * penalties themselves.
293: */
294:
295: int penalty[sizeof(keylist) - 1][2];
296: struct penalty {
297: int value, penalty; /* Penalised value and its penalty. */
298: struct penalty *next;
299: } *penlist[sizeof(keylist) - 1][2];
300:
301: #define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */
302:
303: /*
304: * Add a penalty for the number `value' to the list for operation `op',
305: * operand number `operand' (0 or 1). If we run out of memory, we just
306: * forget about the penalty (how likely is this, anyway?).
307: */
1.7 lukem 308: void
1.1 cgd 309: penalise(value, op, operand)
310: int value, op, operand;
311: {
312: struct penalty *p;
313:
314: op = opnum(op);
315: if ((p = (struct penalty *)malloc((u_int)sizeof(*p))) == NULL)
316: return;
317: p->next = penlist[op][operand];
318: penlist[op][operand] = p;
319: penalty[op][operand] += p->penalty = WRONGPENALTY;
320: p->value = value;
321: }
322:
323: /*
324: * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1)
325: * of operation `op'. The random number we generate is either used directly
326: * as a value, or represents a position in the penalty list. If the latter,
327: * we find the corresponding value and return that, decreasing its penalty.
328: */
1.7 lukem 329: int
1.1 cgd 330: getrandom(maxval, op, operand)
331: int maxval, op, operand;
332: {
333: int value;
1.7 lukem 334: struct penalty **pp, *p;
1.1 cgd 335:
336: op = opnum(op);
337: value = random() % (maxval + penalty[op][operand]);
338:
339: /*
340: * 0 to maxval - 1 is a number to be used directly; bigger values
341: * are positions to be located in the penalty list.
342: */
343: if (value < maxval)
344: return(value);
345: value -= maxval;
346:
347: /*
348: * Find the penalty at position `value'; decrement its penalty and
349: * delete it if it reaches 0; return the corresponding value.
350: */
351: for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) {
352: if (p->penalty > value) {
353: value = p->value;
354: penalty[op][operand]--;
355: if (--(p->penalty) <= 0) {
356: p = p->next;
357: (void)free((char *)*pp);
358: *pp = p;
359: }
360: return(value);
361: }
362: value -= p->penalty;
363: }
364: /*
365: * We can only get here if the value from the penalty[] array doesn't
366: * correspond to the actual sum of penalties in the list. Provide an
367: * obscure message.
368: */
1.7 lukem 369: errx(1, "arithmetic: bug: inconsistent penalties.");
1.1 cgd 370: /* NOTREACHED */
371: }
372:
373: /* Return an index for the character op, which is one of [+-x/]. */
1.7 lukem 374: int
1.1 cgd 375: opnum(op)
376: int op;
377: {
378: char *p;
379:
1.7 lukem 380: if (op == 0 || (p = strchr(keylist, op)) == NULL)
381: errx(1, "arithmetic: bug: op %c not in keylist %s",
382: op, keylist);
1.1 cgd 383: return(p - keylist);
384: }
385:
386: /* Print usage message and quit. */
1.7 lukem 387: void
1.1 cgd 388: usage()
389: {
1.16 christos 390: (void)fprintf(stderr, "Usage: %s [-o +-x/] [-r range]\n",
1.17 cgd 391: getprogname());
1.1 cgd 392: exit(1);
393: }
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