File: | src/games/arithmetic/arithmetic.c |
Warning: | line 126, column 6 Although the value stored to 'argc' is used in the enclosing expression, the value is never actually read from 'argc' |
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1 | /* $OpenBSD: arithmetic.c,v 1.28 2018/12/27 17:27:23 tedu Exp $ */ |
2 | |
3 | /* |
4 | * Copyright (c) 1989, 1993 |
5 | * The Regents of the University of California. All rights reserved. |
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. |
18 | * 3. Neither the name of the University nor the names of its contributors |
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 | |
35 | /* |
36 | * By Eamonn McManus, Trinity College Dublin <emcmanus@cs.tcd.ie>. |
37 | * |
38 | * The operation of this program mimics that of the standard Unix game |
39 | * `arithmetic'. I've made it as close as I could manage without examining |
40 | * the source code. The principal differences are: |
41 | * |
42 | * The method of biasing towards numbers that had wrong answers in the past |
43 | * is different; original `arithmetic' seems to retain the bias forever, |
44 | * whereas this program lets the bias gradually decay as it is used. |
45 | * |
46 | * Original `arithmetic' delays for some period (3 seconds?) after printing |
47 | * the score. I saw no reason for this delay, so I scrapped it. |
48 | * |
49 | * There is no longer a limitation on the maximum range that can be supplied |
50 | * to the program. The original program required it to be less than 100. |
51 | * Anomalous results may occur with this program if ranges big enough to |
52 | * allow overflow are given. |
53 | * |
54 | * I have obviously not attempted to duplicate bugs in the original. It |
55 | * would go into an infinite loop if invoked as `arithmetic / 0'. It also |
56 | * did not recognise an EOF in its input, and would continue trying to read |
57 | * after it. It did not check that the input was a valid number, treating any |
58 | * garbage as 0. Finally, it did not flush stdout after printing its prompt, |
59 | * so in the unlikely event that stdout was not a terminal, it would not work |
60 | * properly. |
61 | */ |
62 | |
63 | #include <err.h> |
64 | #include <ctype.h> |
65 | #include <limits.h> |
66 | #include <signal.h> |
67 | #include <stdio.h> |
68 | #include <stdlib.h> |
69 | #include <string.h> |
70 | #include <time.h> |
71 | #include <unistd.h> |
72 | |
73 | int getrandom(uint32_t, int, int); |
74 | __dead__attribute__((__noreturn__)) void intr(int); |
75 | int opnum(int); |
76 | void penalise(int, int, int); |
77 | int problem(void); |
78 | void showstats(void); |
79 | __dead__attribute__((__noreturn__)) void usage(void); |
80 | |
81 | const char keylist[] = "+-x/"; |
82 | const char defaultkeys[] = "+-"; |
83 | const char *keys = defaultkeys; |
84 | int nkeys = sizeof(defaultkeys) - 1; |
85 | uint32_t rangemax = 10; |
86 | int nright, nwrong; |
87 | time_t qtime; |
88 | #define NQUESTS20 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 | int |
98 | main(int argc, char *argv[]) |
99 | { |
100 | int ch, cnt; |
101 | const char *errstr; |
102 | |
103 | if (pledge("stdio", NULL((void *)0)) == -1) |
104 | err(1, "pledge"); |
105 | |
106 | while ((ch = getopt(argc, argv, "hr:o:")) != -1) |
107 | switch(ch) { |
108 | case 'o': { |
109 | const char *p; |
110 | |
111 | for (p = keys = optarg; *p; ++p) |
112 | if (!strchr(keylist, *p)) |
113 | errx(1, "unknown key."); |
114 | nkeys = p - optarg; |
115 | break; |
116 | } |
117 | case 'r': |
118 | rangemax = strtonum(optarg, 1, (1ULL<<31)-1, &errstr); |
119 | if (errstr) |
120 | errx(1, "invalid range, %s: %s", errstr, optarg); |
121 | break; |
122 | case 'h': |
123 | default: |
124 | usage(); |
125 | } |
126 | if (argc -= optind) |
Although the value stored to 'argc' is used in the enclosing expression, the value is never actually read from 'argc' | |
127 | usage(); |
128 | |
129 | (void)signal(SIGINT2, intr); |
130 | |
131 | /* Now ask the questions. */ |
132 | for (;;) { |
133 | for (cnt = NQUESTS20; cnt--;) |
134 | if (problem() == EOF(-1)) |
135 | intr(0); /* Print score and exit */ |
136 | showstats(); |
137 | } |
138 | } |
139 | |
140 | /* Handle interrupt character. Print score and exit. */ |
141 | void |
142 | intr(int dummy) |
143 | { |
144 | showstats(); |
145 | _exit(0); |
146 | } |
147 | |
148 | /* Print score. Original `arithmetic' had a delay after printing it. */ |
149 | void |
150 | showstats(void) |
151 | { |
152 | if (nright + nwrong > 0) { |
153 | (void)printf("\n\nRights %d; Wrongs %d; Score %d%%", |
154 | nright, nwrong, (int)(100L * nright / (nright + nwrong))); |
155 | if (nright > 0) |
156 | (void)printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n", |
157 | (long)qtime, (float)qtime / nright); |
158 | } |
159 | (void)printf("\n"); |
160 | } |
161 | |
162 | /* |
163 | * Pick a problem and ask it. Keeps asking the same problem until supplied |
164 | * with the correct answer, or until EOF or interrupt is typed. Problems are |
165 | * selected such that the right operand and either the left operand (for +, x) |
166 | * or the correct result (for -, /) are in the range 0 to rangemax. Each wrong |
167 | * answer causes the numbers in the problem to be penalised, so that they are |
168 | * more likely to appear in subsequent problems. |
169 | */ |
170 | int |
171 | problem(void) |
172 | { |
173 | char *p; |
174 | time_t start, finish; |
175 | int left, op, right, result; |
176 | char line[80]; |
177 | |
178 | op = keys[arc4random_uniform(nkeys)]; |
179 | if (op != '/') |
180 | right = getrandom(rangemax + 1, op, 1); |
181 | retry: |
182 | /* Get the operands. */ |
183 | switch (op) { |
184 | case '+': |
185 | left = getrandom(rangemax + 1, op, 0); |
186 | result = left + right; |
187 | break; |
188 | case '-': |
189 | result = getrandom(rangemax + 1, op, 0); |
190 | left = right + result; |
191 | break; |
192 | case 'x': |
193 | left = getrandom(rangemax + 1, op, 0); |
194 | result = left * right; |
195 | break; |
196 | case '/': |
197 | right = getrandom(rangemax, op, 1) + 1; |
198 | result = getrandom(rangemax + 1, op, 0); |
199 | left = right * result + arc4random_uniform(right); |
200 | break; |
201 | } |
202 | |
203 | /* |
204 | * A very big maxrange could cause negative values to pop |
205 | * up, owing to overflow. |
206 | */ |
207 | if (result < 0 || left < 0) |
208 | goto retry; |
209 | |
210 | (void)printf("%d %c %d = ", left, op, right); |
211 | (void)fflush(stdout(&__sF[1])); |
212 | (void)time(&start); |
213 | |
214 | /* |
215 | * Keep looping until the correct answer is given, or until EOF or |
216 | * interrupt is typed. |
217 | */ |
218 | for (;;) { |
219 | if (!fgets(line, sizeof(line), stdin(&__sF[0]))) { |
220 | (void)printf("\n"); |
221 | return(EOF(-1)); |
222 | } |
223 | for (p = line; isspace((unsigned char)*p); ++p); |
224 | if (!isdigit((unsigned char)*p)) { |
225 | (void)printf("Please type a number.\n"); |
226 | continue; |
227 | } |
228 | if (atoi(p) == result) { |
229 | (void)printf("Right!\n"); |
230 | ++nright; |
231 | break; |
232 | } |
233 | /* Wrong answer; penalise and ask again. */ |
234 | (void)printf("What?\n"); |
235 | ++nwrong; |
236 | penalise(right, op, 1); |
237 | if (op == 'x' || op == '+') |
238 | penalise(left, op, 0); |
239 | else |
240 | penalise(result, op, 0); |
241 | } |
242 | |
243 | /* |
244 | * Accumulate the time taken. Obviously rounding errors happen here; |
245 | * however they should cancel out, because some of the time you are |
246 | * charged for a partially elapsed second at the start, and some of |
247 | * the time you are not charged for a partially elapsed second at the |
248 | * end. |
249 | */ |
250 | (void)time(&finish); |
251 | qtime += finish - start; |
252 | return(0); |
253 | } |
254 | |
255 | /* |
256 | * Here is the code for accumulating penalties against the numbers for which |
257 | * a wrong answer was given. The right operand and either the left operand |
258 | * (for +, x) or the result (for -, /) are stored in a list for the particular |
259 | * operation, and each becomes more likely to appear again in that operation. |
260 | * Initially, each number is charged a penalty of WRONGPENALTY, giving it that |
261 | * many extra chances of appearing. Each time it is selected because of this, |
262 | * its penalty is decreased by one; it is removed when it reaches 0. |
263 | * |
264 | * The penalty[] array gives the sum of all penalties in the list for |
265 | * each operation and each operand. The penlist[] array has the lists of |
266 | * penalties themselves. |
267 | */ |
268 | |
269 | uint32_t penalty[sizeof(keylist) - 1][2]; |
270 | struct penalty { |
271 | int value; /* Penalised value. */ |
272 | uint32_t penalty; /* Its penalty. */ |
273 | struct penalty *next; |
274 | } *penlist[sizeof(keylist) - 1][2]; |
275 | |
276 | #define WRONGPENALTY5 5 /* Perhaps this should depend on maxrange. */ |
277 | |
278 | /* |
279 | * Add a penalty for the number `value' to the list for operation `op', |
280 | * operand number `operand' (0 or 1). If we run out of memory, we just |
281 | * forget about the penalty (how likely is this, anyway?). |
282 | */ |
283 | void |
284 | penalise(int value, int op, int operand) |
285 | { |
286 | struct penalty *p; |
287 | |
288 | op = opnum(op); |
289 | if ((p = malloc(sizeof(*p))) == NULL((void *)0)) |
290 | return; |
291 | p->next = penlist[op][operand]; |
292 | penlist[op][operand] = p; |
293 | penalty[op][operand] += p->penalty = WRONGPENALTY5; |
294 | p->value = value; |
295 | } |
296 | |
297 | /* |
298 | * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1) |
299 | * of operation `op'. The random number we generate is either used directly |
300 | * as a value, or represents a position in the penalty list. If the latter, |
301 | * we find the corresponding value and return that, decreasing its penalty. |
302 | */ |
303 | int |
304 | getrandom(uint32_t maxval, int op, int operand) |
305 | { |
306 | uint32_t value; |
307 | struct penalty **pp, *p; |
308 | |
309 | op = opnum(op); |
310 | value = arc4random_uniform(maxval + penalty[op][operand]); |
311 | |
312 | /* |
313 | * 0 to maxval - 1 is a number to be used directly; bigger values |
314 | * are positions to be located in the penalty list. |
315 | */ |
316 | if (value < maxval) |
317 | return((int)value); |
318 | value -= maxval; |
319 | |
320 | /* |
321 | * Find the penalty at position `value'; decrement its penalty and |
322 | * delete it if it reaches 0; return the corresponding value. |
323 | */ |
324 | for (pp = &penlist[op][operand]; (p = *pp) != NULL((void *)0); pp = &p->next) { |
325 | if (p->penalty > value) { |
326 | value = p->value; |
327 | penalty[op][operand]--; |
328 | if (--(p->penalty) <= 0) { |
329 | p = p->next; |
330 | (void)free((char *)*pp); |
331 | *pp = p; |
332 | } |
333 | return(value); |
334 | } |
335 | value -= p->penalty; |
336 | } |
337 | /* |
338 | * We can only get here if the value from the penalty[] array doesn't |
339 | * correspond to the actual sum of penalties in the list. Provide an |
340 | * obscure message. |
341 | */ |
342 | errx(1, "bug: inconsistent penalties."); |
343 | } |
344 | |
345 | /* Return an index for the character op, which is one of [+-x/]. */ |
346 | int |
347 | opnum(int op) |
348 | { |
349 | char *p; |
350 | |
351 | if (op == 0 || (p = strchr(keylist, op)) == NULL((void *)0)) |
352 | errx(1, "bug: op %c not in keylist %s.", op, keylist); |
353 | return(p - keylist); |
354 | } |
355 | |
356 | /* Print usage message and quit. */ |
357 | void |
358 | usage(void) |
359 | { |
360 | extern char *__progname; |
361 | (void)fprintf(stderr(&__sF[2]), "usage: %s [-o +-x/] [-r range]\n", __progname); |
362 | exit(1); |
363 | } |