| 1 | /* |
| 2 | * Copyright (c) 1989, 1993 |
| 3 | * The Regents of the University of California. All rights reserved. |
| 4 | * |
| 5 | * This code is derived from software contributed to Berkeley by |
| 6 | * Eamonn McManus of Trinity College Dublin. |
| 7 | * |
| 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. |
| 35 | * |
| 36 | * @(#) Copyright (c) 1989, 1993 The Regents of the University of California. All rights reserved. |
| 37 | * @(#)arithmetic.c 8.1 (Berkeley) 5/31/93 |
| 38 | * $FreeBSD: src/games/arithmetic/arithmetic.c,v 1.10 1999/12/12 06:40:28 billf Exp $ |
| 39 | * $DragonFly: src/games/arithmetic/arithmetic.c,v 1.4 2005/04/24 15:31:30 liamfoy Exp $ |
| 40 | */ |
| 41 | |
| 42 | /* |
| 43 | * By Eamonn McManus, Trinity College Dublin <emcmanus@cs.tcd.ie>. |
| 44 | * |
| 45 | * The operation of this program mimics that of the standard Unix game |
| 46 | * `arithmetic'. I've made it as close as I could manage without examining |
| 47 | * the source code. The principal differences are: |
| 48 | * |
| 49 | * The method of biasing towards numbers that had wrong answers in the past |
| 50 | * is different; original `arithmetic' seems to retain the bias forever, |
| 51 | * whereas this program lets the bias gradually decay as it is used. |
| 52 | * |
| 53 | * Original `arithmetic' delays for some period (3 seconds?) after printing |
| 54 | * the score. I saw no reason for this delay, so I scrapped it. |
| 55 | * |
| 56 | * There is no longer a limitation on the maximum range that can be supplied |
| 57 | * to the program. The original program required it to be less than 100. |
| 58 | * Anomalous results may occur with this program if ranges big enough to |
| 59 | * allow overflow are given. |
| 60 | * |
| 61 | * I have obviously not attempted to duplicate bugs in the original. It |
| 62 | * would go into an infinite loop if invoked as `arithmetic / 0'. It also |
| 63 | * did not recognise an EOF in its input, and would continue trying to read |
| 64 | * after it. It did not check that the input was a valid number, treating any |
| 65 | * garbage as 0. Finally, it did not flush stdout after printing its prompt, |
| 66 | * so in the unlikely event that stdout was not a terminal, it would not work |
| 67 | * properly. |
| 68 | */ |
| 69 | |
| 70 | #include <sys/types.h> |
| 71 | #include <sys/signal.h> |
| 72 | #include <ctype.h> |
| 73 | #include <stdio.h> |
| 74 | #include <string.h> |
| 75 | #include <stdlib.h> |
| 76 | #include <time.h> |
| 77 | #include <unistd.h> |
| 78 | |
| 79 | const char keylist[] = "+-x/"; |
| 80 | const char defaultkeys[] = "+-"; |
| 81 | const char *keys = defaultkeys; |
| 82 | int nkeys = sizeof(defaultkeys) - 1; |
| 83 | int rangemax = 10; |
| 84 | int nright, nwrong; |
| 85 | time_t qtime; |
| 86 | #define NQUESTS 20 |
| 87 | |
| 88 | static void usage (void); |
| 89 | int getrandom (int, int, int); |
| 90 | void intr (int); |
| 91 | int opnum (int); |
| 92 | void penalise (int, int, int); |
| 93 | int problem (void); |
| 94 | void showstats (void); |
| 95 | |
| 96 | /* |
| 97 | * Select keys from +-x/ to be asked addition, subtraction, multiplication, |
| 98 | * and division problems. More than one key may be given. The default is |
| 99 | * +-. Specify a range to confine the operands to 0 - range. Default upper |
| 100 | * bound is 10. After every NQUESTS questions, statistics on the performance |
| 101 | * so far are printed. |
| 102 | */ |
| 103 | int |
| 104 | main(int argc, char **argv) |
| 105 | { |
| 106 | int ch, cnt; |
| 107 | |
| 108 | /* Revoke setgid privileges */ |
| 109 | setgid(getgid()); |
| 110 | |
| 111 | while ((ch = getopt(argc, argv, "r:o:")) != -1) |
| 112 | switch(ch) { |
| 113 | case 'o': { |
| 114 | const char *p; |
| 115 | |
| 116 | for (p = keys = optarg; *p; ++p) |
| 117 | if (!index(keylist, *p)) { |
| 118 | (void)fprintf(stderr, |
| 119 | "arithmetic: unknown key.\n"); |
| 120 | exit(1); |
| 121 | } |
| 122 | nkeys = p - optarg; |
| 123 | break; |
| 124 | } |
| 125 | case 'r': |
| 126 | if ((rangemax = atoi(optarg)) <= 0) { |
| 127 | (void)fprintf(stderr, |
| 128 | "arithmetic: invalid range.\n"); |
| 129 | exit(1); |
| 130 | } |
| 131 | break; |
| 132 | case '?': |
| 133 | default: |
| 134 | usage(); |
| 135 | } |
| 136 | if (argc -= optind) |
| 137 | usage(); |
| 138 | |
| 139 | /* Seed the random-number generator. */ |
| 140 | srandomdev(); |
| 141 | |
| 142 | (void)signal(SIGINT, intr); |
| 143 | |
| 144 | /* Now ask the questions. */ |
| 145 | for (;;) { |
| 146 | for (cnt = NQUESTS; cnt--;) |
| 147 | if (problem() == EOF) |
| 148 | exit(0); |
| 149 | showstats(); |
| 150 | } |
| 151 | /* NOTREACHED */ |
| 152 | } |
| 153 | |
| 154 | /* Handle interrupt character. Print score and exit. */ |
| 155 | void |
| 156 | intr(__unused int sig) |
| 157 | { |
| 158 | showstats(); |
| 159 | exit(0); |
| 160 | } |
| 161 | |
| 162 | /* Print score. Original `arithmetic' had a delay after printing it. */ |
| 163 | void |
| 164 | showstats(void) |
| 165 | { |
| 166 | if (nright + nwrong > 0) { |
| 167 | (void)printf("\n\nRights %d; Wrongs %d; Score %d%%", |
| 168 | nright, nwrong, (int)(100L * nright / (nright + nwrong))); |
| 169 | if (nright > 0) |
| 170 | (void)printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n", |
| 171 | (long)qtime, (float)qtime / nright); |
| 172 | } |
| 173 | (void)printf("\n"); |
| 174 | } |
| 175 | |
| 176 | /* |
| 177 | * Pick a problem and ask it. Keeps asking the same problem until supplied |
| 178 | * with the correct answer, or until EOF or interrupt is typed. Problems are |
| 179 | * selected such that the right operand and either the left operand (for +, x) |
| 180 | * or the correct result (for -, /) are in the range 0 to rangemax. Each wrong |
| 181 | * answer causes the numbers in the problem to be penalised, so that they are |
| 182 | * more likely to appear in subsequent problems. |
| 183 | */ |
| 184 | int |
| 185 | problem(void) |
| 186 | { |
| 187 | char *p; |
| 188 | time_t start, finish; |
| 189 | int left, op, right, result; |
| 190 | char line[80]; |
| 191 | |
| 192 | left = 0; |
| 193 | right = 0; |
| 194 | result = 0; |
| 195 | op = keys[random() % nkeys]; |
| 196 | if (op != '/') |
| 197 | right = getrandom(rangemax + 1, op, 1); |
| 198 | retry: |
| 199 | /* Get the operands. */ |
| 200 | switch (op) { |
| 201 | case '+': |
| 202 | left = getrandom(rangemax + 1, op, 0); |
| 203 | result = left + right; |
| 204 | break; |
| 205 | case '-': |
| 206 | result = getrandom(rangemax + 1, op, 0); |
| 207 | left = right + result; |
| 208 | break; |
| 209 | case 'x': |
| 210 | left = getrandom(rangemax + 1, op, 0); |
| 211 | result = left * right; |
| 212 | break; |
| 213 | case '/': |
| 214 | right = getrandom(rangemax, op, 1) + 1; |
| 215 | result = getrandom(rangemax + 1, op, 0); |
| 216 | left = right * result + random() % right; |
| 217 | break; |
| 218 | } |
| 219 | |
| 220 | /* |
| 221 | * A very big maxrange could cause negative values to pop |
| 222 | * up, owing to overflow. |
| 223 | */ |
| 224 | if (result < 0 || left < 0) |
| 225 | goto retry; |
| 226 | |
| 227 | (void)printf("%d %c %d = ", left, op, right); |
| 228 | (void)fflush(stdout); |
| 229 | (void)time(&start); |
| 230 | |
| 231 | /* |
| 232 | * Keep looping until the correct answer is given, or until EOF or |
| 233 | * interrupt is typed. |
| 234 | */ |
| 235 | for (;;) { |
| 236 | if (!fgets(line, sizeof(line), stdin)) { |
| 237 | (void)printf("\n"); |
| 238 | return(EOF); |
| 239 | } |
| 240 | for (p = line; *p && isspace(*p); ++p); |
| 241 | if (!isdigit(*p)) { |
| 242 | (void)printf("Please type a number.\n"); |
| 243 | continue; |
| 244 | } |
| 245 | if (atoi(p) == result) { |
| 246 | (void)printf("Right!\n"); |
| 247 | ++nright; |
| 248 | break; |
| 249 | } |
| 250 | /* Wrong answer; penalise and ask again. */ |
| 251 | (void)printf("What?\n"); |
| 252 | ++nwrong; |
| 253 | penalise(right, op, 1); |
| 254 | if (op == 'x' || op == '+') |
| 255 | penalise(left, op, 0); |
| 256 | else |
| 257 | penalise(result, op, 0); |
| 258 | } |
| 259 | |
| 260 | /* |
| 261 | * Accumulate the time taken. Obviously rounding errors happen here; |
| 262 | * however they should cancel out, because some of the time you are |
| 263 | * charged for a partially elapsed second at the start, and some of |
| 264 | * the time you are not charged for a partially elapsed second at the |
| 265 | * end. |
| 266 | */ |
| 267 | (void)time(&finish); |
| 268 | qtime += finish - start; |
| 269 | return(0); |
| 270 | } |
| 271 | |
| 272 | /* |
| 273 | * Here is the code for accumulating penalties against the numbers for which |
| 274 | * a wrong answer was given. The right operand and either the left operand |
| 275 | * (for +, x) or the result (for -, /) are stored in a list for the particular |
| 276 | * operation, and each becomes more likely to appear again in that operation. |
| 277 | * Initially, each number is charged a penalty of WRONGPENALTY, giving it that |
| 278 | * many extra chances of appearing. Each time it is selected because of this, |
| 279 | * its penalty is decreased by one; it is removed when it reaches 0. |
| 280 | * |
| 281 | * The penalty[] array gives the sum of all penalties in the list for |
| 282 | * each operation and each operand. The penlist[] array has the lists of |
| 283 | * penalties themselves. |
| 284 | */ |
| 285 | |
| 286 | int penalty[sizeof(keylist) - 1][2]; |
| 287 | struct penalty { |
| 288 | int value, penalty; /* Penalised value and its penalty. */ |
| 289 | struct penalty *next; |
| 290 | } *penlist[sizeof(keylist) - 1][2]; |
| 291 | |
| 292 | #define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */ |
| 293 | |
| 294 | /* |
| 295 | * Add a penalty for the number `value' to the list for operation `op', |
| 296 | * operand number `operand' (0 or 1). If we run out of memory, we just |
| 297 | * forget about the penalty (how likely is this, anyway?). |
| 298 | */ |
| 299 | void |
| 300 | penalise(int value, int op, int operand) |
| 301 | { |
| 302 | struct penalty *p; |
| 303 | |
| 304 | op = opnum(op); |
| 305 | if ((p = (struct penalty *)malloc((u_int)sizeof(*p))) == NULL) |
| 306 | return; |
| 307 | p->next = penlist[op][operand]; |
| 308 | penlist[op][operand] = p; |
| 309 | penalty[op][operand] += p->penalty = WRONGPENALTY; |
| 310 | p->value = value; |
| 311 | } |
| 312 | |
| 313 | /* |
| 314 | * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1) |
| 315 | * of operation `op'. The random number we generate is either used directly |
| 316 | * as a value, or represents a position in the penalty list. If the latter, |
| 317 | * we find the corresponding value and return that, decreasing its penalty. |
| 318 | */ |
| 319 | int |
| 320 | getrandom(int maxval, int op, int operand) |
| 321 | { |
| 322 | int value; |
| 323 | struct penalty **pp, *p; |
| 324 | |
| 325 | op = opnum(op); |
| 326 | value = random() % (maxval + penalty[op][operand]); |
| 327 | |
| 328 | /* |
| 329 | * 0 to maxval - 1 is a number to be used directly; bigger values |
| 330 | * are positions to be located in the penalty list. |
| 331 | */ |
| 332 | if (value < maxval) |
| 333 | return(value); |
| 334 | value -= maxval; |
| 335 | |
| 336 | /* |
| 337 | * Find the penalty at position `value'; decrement its penalty and |
| 338 | * delete it if it reaches 0; return the corresponding value. |
| 339 | */ |
| 340 | for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) { |
| 341 | if (p->penalty > value) { |
| 342 | value = p->value; |
| 343 | penalty[op][operand]--; |
| 344 | if (--(p->penalty) <= 0) { |
| 345 | p = p->next; |
| 346 | (void)free((char *)*pp); |
| 347 | *pp = p; |
| 348 | } |
| 349 | return(value); |
| 350 | } |
| 351 | value -= p->penalty; |
| 352 | } |
| 353 | /* |
| 354 | * We can only get here if the value from the penalty[] array doesn't |
| 355 | * correspond to the actual sum of penalties in the list. Provide an |
| 356 | * obscure message. |
| 357 | */ |
| 358 | (void)fprintf(stderr, "arithmetic: bug: inconsistent penalties\n"); |
| 359 | exit(1); |
| 360 | /* NOTREACHED */ |
| 361 | } |
| 362 | |
| 363 | /* Return an index for the character op, which is one of [+-x/]. */ |
| 364 | int |
| 365 | opnum(int op) |
| 366 | { |
| 367 | char *p; |
| 368 | |
| 369 | if (op == 0 || (p = index(keylist, op)) == NULL) { |
| 370 | (void)fprintf(stderr, |
| 371 | "arithmetic: bug: op %c not in keylist %s\n", op, keylist); |
| 372 | exit(1); |
| 373 | } |
| 374 | return(p - keylist); |
| 375 | } |
| 376 | |
| 377 | /* Print usage message and quit. */ |
| 378 | static void |
| 379 | usage(void) |
| 380 | { |
| 381 | (void)fprintf(stderr, "usage: arithmetic [-o +-x/] [-r range]\n"); |
| 382 | exit(1); |
| 383 | } |