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afa1807c | 1 | /* |
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2 | * Copyright (c) 1989, 1993 |
3 | * The Regents of the University of California. All rights reserved. | |
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4 | * |
5 | * This code is derived from software contributed to Berkeley by | |
6 | * Eamonn McManus of Trinity College Dublin. | |
7 | * | |
badc70cc | 8 | * %sccs.include.redist.c% |
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9 | */ |
10 | ||
11 | #ifndef lint | |
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12 | static char copyright[] = |
13 | "@(#) Copyright (c) 1989, 1993\n\ | |
14 | The Regents of the University of California. All rights reserved.\n"; | |
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15 | #endif /* not lint */ |
16 | ||
17 | #ifndef lint | |
0749e883 | 18 | static char sccsid[] = "@(#)arithmetic.c 8.1 (Berkeley) %G%"; |
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19 | #endif /* not lint */ |
20 | ||
21 | /* | |
22 | * By Eamonn McManus, Trinity College Dublin <emcmanus@cs.tcd.ie>. | |
23 | * | |
24 | * The operation of this program mimics that of the standard Unix game | |
25 | * `arithmetic'. I've made it as close as I could manage without examining | |
26 | * the source code. The principal differences are: | |
27 | * | |
28 | * The method of biasing towards numbers that had wrong answers in the past | |
29 | * is different; original `arithmetic' seems to retain the bias forever, | |
30 | * whereas this program lets the bias gradually decay as it is used. | |
31 | * | |
32 | * Original `arithmetic' delays for some period (3 seconds?) after printing | |
33 | * the score. I saw no reason for this delay, so I scrapped it. | |
34 | * | |
35 | * There is no longer a limitation on the maximum range that can be supplied | |
36 | * to the program. The original program required it to be less than 100. | |
37 | * Anomalous results may occur with this program if ranges big enough to | |
38 | * allow overflow are given. | |
39 | * | |
40 | * I have obviously not attempted to duplicate bugs in the original. It | |
41 | * would go into an infinite loop if invoked as `arithmetic / 0'. It also | |
42 | * did not recognise an EOF in its input, and would continue trying to read | |
43 | * after it. It did not check that the input was a valid number, treating any | |
44 | * garbage as 0. Finally, it did not flush stdout after printing its prompt, | |
45 | * so in the unlikely event that stdout was not a terminal, it would not work | |
46 | * properly. | |
47 | */ | |
48 | ||
49 | #include <sys/types.h> | |
50 | #include <sys/signal.h> | |
51 | #include <ctype.h> | |
ec93545d | 52 | #include <stdio.h> |
6ebcb998 | 53 | #include <string.h> |
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54 | |
55 | char keylist[] = "+-x/"; | |
56 | char defaultkeys[] = "+-"; | |
57 | char *keys = defaultkeys; | |
58 | int nkeys = sizeof(defaultkeys) - 1; | |
59 | int rangemax = 10; | |
60 | int nright, nwrong; | |
61 | time_t qtime; | |
62 | #define NQUESTS 20 | |
63 | ||
64 | /* | |
65 | * Select keys from +-x/ to be asked addition, subtraction, multiplication, | |
66 | * and division problems. More than one key may be given. The default is | |
67 | * +-. Specify a range to confine the operands to 0 - range. Default upper | |
68 | * bound is 10. After every NQUESTS questions, statistics on the performance | |
69 | * so far are printed. | |
70 | */ | |
71 | void | |
72 | main(argc, argv) | |
73 | int argc; | |
74 | char **argv; | |
ec93545d | 75 | { |
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76 | extern char *optarg; |
77 | extern int optind; | |
78 | int ch, cnt; | |
828b93b9 | 79 | void intr(); |
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80 | |
81 | while ((ch = getopt(argc, argv, "r:o:")) != EOF) | |
82 | switch(ch) { | |
83 | case 'o': { | |
84 | register char *p; | |
85 | ||
86 | for (p = keys = optarg; *p; ++p) | |
87 | if (!index(keylist, *p)) { | |
88 | (void)fprintf(stderr, | |
89 | "arithmetic: unknown key.\n"); | |
90 | exit(1); | |
91 | } | |
92 | nkeys = p - optarg; | |
ec93545d | 93 | break; |
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94 | } |
95 | case 'r': | |
96 | if ((rangemax = atoi(optarg)) <= 0) { | |
97 | (void)fprintf(stderr, | |
98 | "arithmetic: invalid range.\n"); | |
99 | exit(1); | |
100 | } | |
101 | break; | |
102 | case '?': | |
ec93545d | 103 | default: |
afa1807c | 104 | usage(); |
ec93545d | 105 | } |
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106 | if (argc -= optind) |
107 | usage(); | |
108 | ||
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109 | /* Seed the random-number generator. */ |
110 | srandom((int)time((time_t *)NULL)); | |
ec93545d | 111 | |
afa1807c | 112 | (void)signal(SIGINT, intr); |
ec93545d | 113 | |
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114 | /* Now ask the questions. */ |
115 | for (;;) { | |
116 | for (cnt = NQUESTS; cnt--;) | |
117 | if (problem() == EOF) | |
118 | exit(0); | |
119 | showstats(); | |
ec93545d | 120 | } |
afa1807c | 121 | /* NOTREACHED */ |
ec93545d KM |
122 | } |
123 | ||
afa1807c | 124 | /* Handle interrupt character. Print score and exit. */ |
828b93b9 | 125 | void |
afa1807c | 126 | intr() |
ec93545d | 127 | { |
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128 | showstats(); |
129 | exit(0); | |
ec93545d KM |
130 | } |
131 | ||
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132 | /* Print score. Original `arithmetic' had a delay after printing it. */ |
133 | showstats() | |
ec93545d | 134 | { |
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135 | if (nright + nwrong > 0) { |
136 | (void)printf("\n\nRights %d; Wrongs %d; Score %d%%", | |
137 | nright, nwrong, (int)(100L * nright / (nright + nwrong))); | |
138 | if (nright > 0) | |
139 | (void)printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n", | |
140 | (long)qtime, (float)qtime / nright); | |
ec93545d | 141 | } |
afa1807c | 142 | (void)printf("\n"); |
ec93545d KM |
143 | } |
144 | ||
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145 | /* |
146 | * Pick a problem and ask it. Keeps asking the same problem until supplied | |
147 | * with the correct answer, or until EOF or interrupt is typed. Problems are | |
148 | * selected such that the right operand and either the left operand (for +, x) | |
149 | * or the correct result (for -, /) are in the range 0 to rangemax. Each wrong | |
150 | * answer causes the numbers in the problem to be penalised, so that they are | |
151 | * more likely to appear in subsequent problems. | |
152 | */ | |
153 | problem() | |
ec93545d | 154 | { |
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155 | register char *p; |
156 | time_t start, finish; | |
157 | int left, op, right, result; | |
158 | char line[80]; | |
159 | ||
160 | op = keys[random() % nkeys]; | |
161 | if (op != '/') | |
162 | right = getrandom(rangemax + 1, op, 1); | |
163 | retry: | |
164 | /* Get the operands. */ | |
165 | switch (op) { | |
166 | case '+': | |
167 | left = getrandom(rangemax + 1, op, 0); | |
168 | result = left + right; | |
169 | break; | |
170 | case '-': | |
171 | result = getrandom(rangemax + 1, op, 0); | |
172 | left = right + result; | |
173 | break; | |
174 | case 'x': | |
175 | left = getrandom(rangemax + 1, op, 0); | |
176 | result = left * right; | |
177 | break; | |
178 | case '/': | |
179 | right = getrandom(rangemax, op, 1) + 1; | |
180 | result = getrandom(rangemax + 1, op, 0); | |
181 | left = right * result + random() % right; | |
182 | break; | |
183 | } | |
ec93545d | 184 | |
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185 | /* |
186 | * A very big maxrange could cause negative values to pop | |
187 | * up, owing to overflow. | |
188 | */ | |
189 | if (result < 0 || left < 0) | |
190 | goto retry; | |
191 | ||
192 | (void)printf("%d %c %d = ", left, op, right); | |
193 | (void)fflush(stdout); | |
194 | (void)time(&start); | |
195 | ||
196 | /* | |
197 | * Keep looping until the correct answer is given, or until EOF or | |
198 | * interrupt is typed. | |
199 | */ | |
200 | for (;;) { | |
201 | if (!fgets(line, sizeof(line), stdin)) { | |
202 | (void)printf("\n"); | |
203 | return(EOF); | |
204 | } | |
205 | for (p = line; *p && isspace(*p); ++p); | |
206 | if (!isdigit(*p)) { | |
207 | (void)printf("Please type a number.\n"); | |
208 | continue; | |
209 | } | |
210 | if (atoi(p) == result) { | |
211 | (void)printf("Right!\n"); | |
212 | ++nright; | |
213 | break; | |
214 | } | |
215 | /* Wrong answer; penalise and ask again. */ | |
216 | (void)printf("What?\n"); | |
217 | ++nwrong; | |
218 | penalise(right, op, 1); | |
219 | if (op == 'x' || op == '+') | |
220 | penalise(left, op, 0); | |
221 | else | |
222 | penalise(result, op, 0); | |
223 | } | |
ec93545d | 224 | |
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225 | /* |
226 | * Accumulate the time taken. Obviously rounding errors happen here; | |
227 | * however they should cancel out, because some of the time you are | |
228 | * charged for a partially elapsed second at the start, and some of | |
229 | * the time you are not charged for a partially elapsed second at the | |
230 | * end. | |
231 | */ | |
232 | (void)time(&finish); | |
233 | qtime += finish - start; | |
234 | return(0); | |
ec93545d KM |
235 | } |
236 | ||
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237 | /* |
238 | * Here is the code for accumulating penalties against the numbers for which | |
239 | * a wrong answer was given. The right operand and either the left operand | |
240 | * (for +, x) or the result (for -, /) are stored in a list for the particular | |
241 | * operation, and each becomes more likely to appear again in that operation. | |
242 | * Initially, each number is charged a penalty of WRONGPENALTY, giving it that | |
243 | * many extra chances of appearing. Each time it is selected because of this, | |
244 | * its penalty is decreased by one; it is removed when it reaches 0. | |
245 | * | |
246 | * The penalty[] array gives the sum of all penalties in the list for | |
247 | * each operation and each operand. The penlist[] array has the lists of | |
248 | * penalties themselves. | |
249 | */ | |
250 | ||
251 | int penalty[sizeof(keylist) - 1][2]; | |
252 | struct penalty { | |
253 | int value, penalty; /* Penalised value and its penalty. */ | |
254 | struct penalty *next; | |
255 | } *penlist[sizeof(keylist) - 1][2]; | |
256 | ||
257 | #define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */ | |
258 | ||
259 | /* | |
260 | * Add a penalty for the number `value' to the list for operation `op', | |
261 | * operand number `operand' (0 or 1). If we run out of memory, we just | |
262 | * forget about the penalty (how likely is this, anyway?). | |
263 | */ | |
264 | penalise(value, op, operand) | |
265 | int value, op, operand; | |
ec93545d | 266 | { |
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267 | struct penalty *p; |
268 | char *malloc(); | |
269 | ||
270 | op = opnum(op); | |
271 | if ((p = (struct penalty *)malloc((u_int)sizeof(*p))) == NULL) | |
272 | return; | |
273 | p->next = penlist[op][operand]; | |
274 | penlist[op][operand] = p; | |
275 | penalty[op][operand] += p->penalty = WRONGPENALTY; | |
276 | p->value = value; | |
ec93545d KM |
277 | } |
278 | ||
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279 | /* |
280 | * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1) | |
281 | * of operation `op'. The random number we generate is either used directly | |
282 | * as a value, or represents a position in the penalty list. If the latter, | |
283 | * we find the corresponding value and return that, decreasing its penalty. | |
284 | */ | |
285 | getrandom(maxval, op, operand) | |
286 | int maxval, op, operand; | |
287 | { | |
288 | int value; | |
289 | register struct penalty **pp, *p; | |
290 | ||
291 | op = opnum(op); | |
292 | value = random() % (maxval + penalty[op][operand]); | |
293 | ||
294 | /* | |
295 | * 0 to maxval - 1 is a number to be used directly; bigger values | |
296 | * are positions to be located in the penalty list. | |
297 | */ | |
298 | if (value < maxval) | |
299 | return(value); | |
300 | value -= maxval; | |
301 | ||
302 | /* | |
303 | * Find the penalty at position `value'; decrement its penalty and | |
304 | * delete it if it reaches 0; return the corresponding value. | |
305 | */ | |
306 | for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) { | |
307 | if (p->penalty > value) { | |
308 | value = p->value; | |
309 | penalty[op][operand]--; | |
310 | if (--(p->penalty) <= 0) { | |
311 | p = p->next; | |
312 | (void)free((char *)*pp); | |
313 | *pp = p; | |
314 | } | |
315 | return(value); | |
316 | } | |
317 | value -= p->penalty; | |
ec93545d | 318 | } |
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319 | /* |
320 | * We can only get here if the value from the penalty[] array doesn't | |
321 | * correspond to the actual sum of penalties in the list. Provide an | |
322 | * obscure message. | |
323 | */ | |
324 | (void)fprintf(stderr, "arithmetic: bug: inconsistent penalties\n"); | |
325 | exit(1); | |
326 | /* NOTREACHED */ | |
327 | } | |
ec93545d | 328 | |
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329 | /* Return an index for the character op, which is one of [+-x/]. */ |
330 | opnum(op) | |
331 | int op; | |
ec93545d | 332 | { |
afa1807c | 333 | char *p; |
ec93545d | 334 | |
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335 | if (op == 0 || (p = index(keylist, op)) == NULL) { |
336 | (void)fprintf(stderr, | |
337 | "arithmetic: bug: op %c not in keylist %s\n", op, keylist); | |
338 | exit(1); | |
339 | } | |
340 | return(p - keylist); | |
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341 | } |
342 | ||
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343 | /* Print usage message and quit. */ |
344 | usage() | |
ec93545d | 345 | { |
2e5afe14 | 346 | (void)fprintf(stderr, "usage: arithmetic [-o +-x/] [-r range]\n"); |
afa1807c | 347 | exit(1); |
ec93545d | 348 | } |