| 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 | } |