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1 | /* |
2 | * Copyright (c) 1989 The Regents of the University of California. | |
3 | * All rights reserved. | |
4 | * | |
5 | * This code is derived from software contributed to Berkeley by | |
6 | * Eamonn McManus of Trinity College Dublin. | |
7 | * | |
af359dea C |
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 | ||
37 | #ifndef lint | |
38 | char copyright[] = | |
39 | "@(#) Copyright (c) 1989 The Regents of the University of California.\n\ | |
40 | All rights reserved.\n"; | |
41 | #endif /* not lint */ | |
42 | ||
43 | #ifndef lint | |
af359dea | 44 | static char sccsid[] = "@(#)arithmetic.c 5.5 (Berkeley) 2/27/91"; |
afa1807c KB |
45 | #endif /* not lint */ |
46 | ||
47 | /* | |
48 | * By Eamonn McManus, Trinity College Dublin <emcmanus@cs.tcd.ie>. | |
49 | * | |
50 | * The operation of this program mimics that of the standard Unix game | |
51 | * `arithmetic'. I've made it as close as I could manage without examining | |
52 | * the source code. The principal differences are: | |
53 | * | |
54 | * The method of biasing towards numbers that had wrong answers in the past | |
55 | * is different; original `arithmetic' seems to retain the bias forever, | |
56 | * whereas this program lets the bias gradually decay as it is used. | |
57 | * | |
58 | * Original `arithmetic' delays for some period (3 seconds?) after printing | |
59 | * the score. I saw no reason for this delay, so I scrapped it. | |
60 | * | |
61 | * There is no longer a limitation on the maximum range that can be supplied | |
62 | * to the program. The original program required it to be less than 100. | |
63 | * Anomalous results may occur with this program if ranges big enough to | |
64 | * allow overflow are given. | |
65 | * | |
66 | * I have obviously not attempted to duplicate bugs in the original. It | |
67 | * would go into an infinite loop if invoked as `arithmetic / 0'. It also | |
68 | * did not recognise an EOF in its input, and would continue trying to read | |
69 | * after it. It did not check that the input was a valid number, treating any | |
70 | * garbage as 0. Finally, it did not flush stdout after printing its prompt, | |
71 | * so in the unlikely event that stdout was not a terminal, it would not work | |
72 | * properly. | |
73 | */ | |
74 | ||
75 | #include <sys/types.h> | |
76 | #include <sys/signal.h> | |
77 | #include <ctype.h> | |
ec93545d | 78 | #include <stdio.h> |
6ebcb998 | 79 | #include <string.h> |
afa1807c KB |
80 | |
81 | char keylist[] = "+-x/"; | |
82 | char defaultkeys[] = "+-"; | |
83 | char *keys = defaultkeys; | |
84 | int nkeys = sizeof(defaultkeys) - 1; | |
85 | int rangemax = 10; | |
86 | int nright, nwrong; | |
87 | time_t qtime; | |
88 | #define NQUESTS 20 | |
89 | ||
90 | /* | |
91 | * Select keys from +-x/ to be asked addition, subtraction, multiplication, | |
92 | * and division problems. More than one key may be given. The default is | |
93 | * +-. Specify a range to confine the operands to 0 - range. Default upper | |
94 | * bound is 10. After every NQUESTS questions, statistics on the performance | |
95 | * so far are printed. | |
96 | */ | |
97 | void | |
98 | main(argc, argv) | |
99 | int argc; | |
100 | char **argv; | |
ec93545d | 101 | { |
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102 | extern char *optarg; |
103 | extern int optind; | |
104 | int ch, cnt; | |
105 | time_t time(); | |
828b93b9 | 106 | void intr(); |
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107 | |
108 | while ((ch = getopt(argc, argv, "r:o:")) != EOF) | |
109 | switch(ch) { | |
110 | case 'o': { | |
111 | register char *p; | |
112 | ||
113 | for (p = keys = optarg; *p; ++p) | |
114 | if (!index(keylist, *p)) { | |
115 | (void)fprintf(stderr, | |
116 | "arithmetic: unknown key.\n"); | |
117 | exit(1); | |
118 | } | |
119 | nkeys = p - optarg; | |
ec93545d | 120 | break; |
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121 | } |
122 | case 'r': | |
123 | if ((rangemax = atoi(optarg)) <= 0) { | |
124 | (void)fprintf(stderr, | |
125 | "arithmetic: invalid range.\n"); | |
126 | exit(1); | |
127 | } | |
128 | break; | |
129 | case '?': | |
ec93545d | 130 | default: |
afa1807c | 131 | usage(); |
ec93545d | 132 | } |
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133 | if (argc -= optind) |
134 | usage(); | |
135 | ||
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136 | /* Seed the random-number generator. */ |
137 | srandom((int)time((time_t *)NULL)); | |
ec93545d | 138 | |
afa1807c | 139 | (void)signal(SIGINT, intr); |
ec93545d | 140 | |
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141 | /* Now ask the questions. */ |
142 | for (;;) { | |
143 | for (cnt = NQUESTS; cnt--;) | |
144 | if (problem() == EOF) | |
145 | exit(0); | |
146 | showstats(); | |
ec93545d | 147 | } |
afa1807c | 148 | /* NOTREACHED */ |
ec93545d KM |
149 | } |
150 | ||
afa1807c | 151 | /* Handle interrupt character. Print score and exit. */ |
828b93b9 | 152 | void |
afa1807c | 153 | intr() |
ec93545d | 154 | { |
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155 | showstats(); |
156 | exit(0); | |
ec93545d KM |
157 | } |
158 | ||
afa1807c KB |
159 | /* Print score. Original `arithmetic' had a delay after printing it. */ |
160 | showstats() | |
ec93545d | 161 | { |
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162 | if (nright + nwrong > 0) { |
163 | (void)printf("\n\nRights %d; Wrongs %d; Score %d%%", | |
164 | nright, nwrong, (int)(100L * nright / (nright + nwrong))); | |
165 | if (nright > 0) | |
166 | (void)printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n", | |
167 | (long)qtime, (float)qtime / nright); | |
ec93545d | 168 | } |
afa1807c | 169 | (void)printf("\n"); |
ec93545d KM |
170 | } |
171 | ||
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172 | /* |
173 | * Pick a problem and ask it. Keeps asking the same problem until supplied | |
174 | * with the correct answer, or until EOF or interrupt is typed. Problems are | |
175 | * selected such that the right operand and either the left operand (for +, x) | |
176 | * or the correct result (for -, /) are in the range 0 to rangemax. Each wrong | |
177 | * answer causes the numbers in the problem to be penalised, so that they are | |
178 | * more likely to appear in subsequent problems. | |
179 | */ | |
180 | problem() | |
ec93545d | 181 | { |
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182 | register char *p; |
183 | time_t start, finish; | |
184 | int left, op, right, result; | |
185 | char line[80]; | |
186 | ||
187 | op = keys[random() % nkeys]; | |
188 | if (op != '/') | |
189 | right = getrandom(rangemax + 1, op, 1); | |
190 | retry: | |
191 | /* Get the operands. */ | |
192 | switch (op) { | |
193 | case '+': | |
194 | left = getrandom(rangemax + 1, op, 0); | |
195 | result = left + right; | |
196 | break; | |
197 | case '-': | |
198 | result = getrandom(rangemax + 1, op, 0); | |
199 | left = right + result; | |
200 | break; | |
201 | case 'x': | |
202 | left = getrandom(rangemax + 1, op, 0); | |
203 | result = left * right; | |
204 | break; | |
205 | case '/': | |
206 | right = getrandom(rangemax, op, 1) + 1; | |
207 | result = getrandom(rangemax + 1, op, 0); | |
208 | left = right * result + random() % right; | |
209 | break; | |
210 | } | |
ec93545d | 211 | |
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212 | /* |
213 | * A very big maxrange could cause negative values to pop | |
214 | * up, owing to overflow. | |
215 | */ | |
216 | if (result < 0 || left < 0) | |
217 | goto retry; | |
218 | ||
219 | (void)printf("%d %c %d = ", left, op, right); | |
220 | (void)fflush(stdout); | |
221 | (void)time(&start); | |
222 | ||
223 | /* | |
224 | * Keep looping until the correct answer is given, or until EOF or | |
225 | * interrupt is typed. | |
226 | */ | |
227 | for (;;) { | |
228 | if (!fgets(line, sizeof(line), stdin)) { | |
229 | (void)printf("\n"); | |
230 | return(EOF); | |
231 | } | |
232 | for (p = line; *p && isspace(*p); ++p); | |
233 | if (!isdigit(*p)) { | |
234 | (void)printf("Please type a number.\n"); | |
235 | continue; | |
236 | } | |
237 | if (atoi(p) == result) { | |
238 | (void)printf("Right!\n"); | |
239 | ++nright; | |
240 | break; | |
241 | } | |
242 | /* Wrong answer; penalise and ask again. */ | |
243 | (void)printf("What?\n"); | |
244 | ++nwrong; | |
245 | penalise(right, op, 1); | |
246 | if (op == 'x' || op == '+') | |
247 | penalise(left, op, 0); | |
248 | else | |
249 | penalise(result, op, 0); | |
250 | } | |
ec93545d | 251 | |
afa1807c KB |
252 | /* |
253 | * Accumulate the time taken. Obviously rounding errors happen here; | |
254 | * however they should cancel out, because some of the time you are | |
255 | * charged for a partially elapsed second at the start, and some of | |
256 | * the time you are not charged for a partially elapsed second at the | |
257 | * end. | |
258 | */ | |
259 | (void)time(&finish); | |
260 | qtime += finish - start; | |
261 | return(0); | |
ec93545d KM |
262 | } |
263 | ||
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264 | /* |
265 | * Here is the code for accumulating penalties against the numbers for which | |
266 | * a wrong answer was given. The right operand and either the left operand | |
267 | * (for +, x) or the result (for -, /) are stored in a list for the particular | |
268 | * operation, and each becomes more likely to appear again in that operation. | |
269 | * Initially, each number is charged a penalty of WRONGPENALTY, giving it that | |
270 | * many extra chances of appearing. Each time it is selected because of this, | |
271 | * its penalty is decreased by one; it is removed when it reaches 0. | |
272 | * | |
273 | * The penalty[] array gives the sum of all penalties in the list for | |
274 | * each operation and each operand. The penlist[] array has the lists of | |
275 | * penalties themselves. | |
276 | */ | |
277 | ||
278 | int penalty[sizeof(keylist) - 1][2]; | |
279 | struct penalty { | |
280 | int value, penalty; /* Penalised value and its penalty. */ | |
281 | struct penalty *next; | |
282 | } *penlist[sizeof(keylist) - 1][2]; | |
283 | ||
284 | #define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */ | |
285 | ||
286 | /* | |
287 | * Add a penalty for the number `value' to the list for operation `op', | |
288 | * operand number `operand' (0 or 1). If we run out of memory, we just | |
289 | * forget about the penalty (how likely is this, anyway?). | |
290 | */ | |
291 | penalise(value, op, operand) | |
292 | int value, op, operand; | |
ec93545d | 293 | { |
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294 | struct penalty *p; |
295 | char *malloc(); | |
296 | ||
297 | op = opnum(op); | |
298 | if ((p = (struct penalty *)malloc((u_int)sizeof(*p))) == NULL) | |
299 | return; | |
300 | p->next = penlist[op][operand]; | |
301 | penlist[op][operand] = p; | |
302 | penalty[op][operand] += p->penalty = WRONGPENALTY; | |
303 | p->value = value; | |
ec93545d KM |
304 | } |
305 | ||
afa1807c KB |
306 | /* |
307 | * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1) | |
308 | * of operation `op'. The random number we generate is either used directly | |
309 | * as a value, or represents a position in the penalty list. If the latter, | |
310 | * we find the corresponding value and return that, decreasing its penalty. | |
311 | */ | |
312 | getrandom(maxval, op, operand) | |
313 | int maxval, op, operand; | |
314 | { | |
315 | int value; | |
316 | register struct penalty **pp, *p; | |
317 | ||
318 | op = opnum(op); | |
319 | value = random() % (maxval + penalty[op][operand]); | |
320 | ||
321 | /* | |
322 | * 0 to maxval - 1 is a number to be used directly; bigger values | |
323 | * are positions to be located in the penalty list. | |
324 | */ | |
325 | if (value < maxval) | |
326 | return(value); | |
327 | value -= maxval; | |
328 | ||
329 | /* | |
330 | * Find the penalty at position `value'; decrement its penalty and | |
331 | * delete it if it reaches 0; return the corresponding value. | |
332 | */ | |
333 | for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) { | |
334 | if (p->penalty > value) { | |
335 | value = p->value; | |
336 | penalty[op][operand]--; | |
337 | if (--(p->penalty) <= 0) { | |
338 | p = p->next; | |
339 | (void)free((char *)*pp); | |
340 | *pp = p; | |
341 | } | |
342 | return(value); | |
343 | } | |
344 | value -= p->penalty; | |
ec93545d | 345 | } |
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346 | /* |
347 | * We can only get here if the value from the penalty[] array doesn't | |
348 | * correspond to the actual sum of penalties in the list. Provide an | |
349 | * obscure message. | |
350 | */ | |
351 | (void)fprintf(stderr, "arithmetic: bug: inconsistent penalties\n"); | |
352 | exit(1); | |
353 | /* NOTREACHED */ | |
354 | } | |
ec93545d | 355 | |
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356 | /* Return an index for the character op, which is one of [+-x/]. */ |
357 | opnum(op) | |
358 | int op; | |
ec93545d | 359 | { |
afa1807c | 360 | char *p; |
ec93545d | 361 | |
afa1807c KB |
362 | if (op == 0 || (p = index(keylist, op)) == NULL) { |
363 | (void)fprintf(stderr, | |
364 | "arithmetic: bug: op %c not in keylist %s\n", op, keylist); | |
365 | exit(1); | |
366 | } | |
367 | return(p - keylist); | |
ec93545d KM |
368 | } |
369 | ||
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370 | /* Print usage message and quit. */ |
371 | usage() | |
ec93545d | 372 | { |
2e5afe14 | 373 | (void)fprintf(stderr, "usage: arithmetic [-o +-x/] [-r range]\n"); |
afa1807c | 374 | exit(1); |
ec93545d | 375 | } |