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. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#) Copyright (c) 1989, 1993 The Regents of the University of California. All rights reserved. 33 * @(#)arithmetic.c 8.1 (Berkeley) 5/31/93 34 * $FreeBSD: src/games/arithmetic/arithmetic.c,v 1.10 1999/12/12 06:40:28 billf Exp $ 35 * $DragonFly: src/games/arithmetic/arithmetic.c,v 1.4 2005/04/24 15:31:30 liamfoy Exp $ 36 */ 37 38 /* 39 * By Eamonn McManus, Trinity College Dublin <emcmanus@cs.tcd.ie>. 40 * 41 * The operation of this program mimics that of the standard Unix game 42 * `arithmetic'. I've made it as close as I could manage without examining 43 * the source code. The principal differences are: 44 * 45 * The method of biasing towards numbers that had wrong answers in the past 46 * is different; original `arithmetic' seems to retain the bias forever, 47 * whereas this program lets the bias gradually decay as it is used. 48 * 49 * Original `arithmetic' delays for some period (3 seconds?) after printing 50 * the score. I saw no reason for this delay, so I scrapped it. 51 * 52 * There is no longer a limitation on the maximum range that can be supplied 53 * to the program. The original program required it to be less than 100. 54 * Anomalous results may occur with this program if ranges big enough to 55 * allow overflow are given. 56 * 57 * I have obviously not attempted to duplicate bugs in the original. It 58 * would go into an infinite loop if invoked as `arithmetic / 0'. It also 59 * did not recognise an EOF in its input, and would continue trying to read 60 * after it. It did not check that the input was a valid number, treating any 61 * garbage as 0. Finally, it did not flush stdout after printing its prompt, 62 * so in the unlikely event that stdout was not a terminal, it would not work 63 * properly. 64 */ 65 66 #include <sys/types.h> 67 #include <ctype.h> 68 #include <signal.h> 69 #include <stdio.h> 70 #include <stdlib.h> 71 #include <string.h> 72 #include <time.h> 73 #include <unistd.h> 74 75 int getrandom(int, int, int); 76 void intr(int); 77 int opnum(int); 78 void penalise(int, int, int); 79 int problem(void); 80 void showstats(void); 81 static void usage(void); 82 83 const char keylist[] = "+-x/"; 84 const char defaultkeys[] = "+-"; 85 const char *keys = defaultkeys; 86 int nkeys = sizeof(defaultkeys) - 1; 87 int rangemax = 10; 88 int nright, nwrong; 89 time_t qtime; 90 #define NQUESTS 20 91 92 /* 93 * Select keys from +-x/ to be asked addition, subtraction, multiplication, 94 * and division problems. More than one key may be given. The default is 95 * +-. Specify a range to confine the operands to 0 - range. Default upper 96 * bound is 10. After every NQUESTS questions, statistics on the performance 97 * so far are printed. 98 */ 99 int 100 main(int argc, char *argv[]) 101 { 102 int ch, cnt; 103 104 /* Revoke setgid privileges */ 105 setgid(getgid()); 106 107 while ((ch = getopt(argc, argv, "r:o:")) != -1) 108 switch(ch) { 109 case 'o': { 110 const char *p; 111 112 for (p = keys = optarg; *p; ++p) 113 if (!index(keylist, *p)) { 114 (void)fprintf(stderr, 115 "arithmetic: unknown key.\n"); 116 exit(1); 117 } 118 nkeys = p - optarg; 119 break; 120 } 121 case 'r': 122 if ((rangemax = atoi(optarg)) <= 0) { 123 (void)fprintf(stderr, 124 "arithmetic: invalid range.\n"); 125 exit(1); 126 } 127 break; 128 case '?': 129 default: 130 usage(); 131 } 132 if (argc -= optind) 133 usage(); 134 135 /* Seed the random-number generator. */ 136 srandomdev(); 137 138 (void)signal(SIGINT, intr); 139 140 /* Now ask the questions. */ 141 for (;;) { 142 for (cnt = NQUESTS; cnt--;) 143 if (problem() == EOF) 144 exit(0); 145 showstats(); 146 } 147 /* NOTREACHED */ 148 } 149 150 /* Handle interrupt character. Print score and exit. */ 151 void 152 intr(__unused int sig) 153 { 154 showstats(); 155 exit(0); 156 } 157 158 /* Print score. Original `arithmetic' had a delay after printing it. */ 159 void 160 showstats(void) 161 { 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); 168 } 169 (void)printf("\n"); 170 } 171 172 /* 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 int 181 problem(void) 182 { 183 char *p; 184 time_t start, finish; 185 int left, op, right, result; 186 char line[80]; 187 188 left = 0; 189 right = 0; 190 result = 0; 191 op = keys[random() % nkeys]; 192 if (op != '/') 193 right = getrandom(rangemax + 1, op, 1); 194 retry: 195 /* Get the operands. */ 196 switch (op) { 197 case '+': 198 left = getrandom(rangemax + 1, op, 0); 199 result = left + right; 200 break; 201 case '-': 202 result = getrandom(rangemax + 1, op, 0); 203 left = right + result; 204 break; 205 case 'x': 206 left = getrandom(rangemax + 1, op, 0); 207 result = left * right; 208 break; 209 case '/': 210 right = getrandom(rangemax, op, 1) + 1; 211 result = getrandom(rangemax + 1, op, 0); 212 left = right * result + random() % right; 213 break; 214 } 215 216 /* 217 * A very big maxrange could cause negative values to pop 218 * up, owing to overflow. 219 */ 220 if (result < 0 || left < 0) 221 goto retry; 222 223 (void)printf("%d %c %d = ", left, op, right); 224 (void)fflush(stdout); 225 (void)time(&start); 226 227 /* 228 * Keep looping until the correct answer is given, or until EOF or 229 * interrupt is typed. 230 */ 231 for (;;) { 232 if (!fgets(line, sizeof(line), stdin)) { 233 (void)printf("\n"); 234 return(EOF); 235 } 236 for (p = line; *p && isspace(*p); ++p); 237 if (!isdigit(*p)) { 238 (void)printf("Please type a number.\n"); 239 continue; 240 } 241 if (atoi(p) == result) { 242 (void)printf("Right!\n"); 243 ++nright; 244 break; 245 } 246 /* Wrong answer; penalise and ask again. */ 247 (void)printf("What?\n"); 248 ++nwrong; 249 penalise(right, op, 1); 250 if (op == 'x' || op == '+') 251 penalise(left, op, 0); 252 else 253 penalise(result, op, 0); 254 } 255 256 /* 257 * Accumulate the time taken. Obviously rounding errors happen here; 258 * however they should cancel out, because some of the time you are 259 * charged for a partially elapsed second at the start, and some of 260 * the time you are not charged for a partially elapsed second at the 261 * end. 262 */ 263 (void)time(&finish); 264 qtime += finish - start; 265 return(0); 266 } 267 268 /* 269 * Here is the code for accumulating penalties against the numbers for which 270 * a wrong answer was given. The right operand and either the left operand 271 * (for +, x) or the result (for -, /) are stored in a list for the particular 272 * operation, and each becomes more likely to appear again in that operation. 273 * Initially, each number is charged a penalty of WRONGPENALTY, giving it that 274 * many extra chances of appearing. Each time it is selected because of this, 275 * its penalty is decreased by one; it is removed when it reaches 0. 276 * 277 * The penalty[] array gives the sum of all penalties in the list for 278 * each operation and each operand. The penlist[] array has the lists of 279 * penalties themselves. 280 */ 281 282 int penalty[sizeof(keylist) - 1][2]; 283 struct penalty { 284 int value, penalty; /* Penalised value and its penalty. */ 285 struct penalty *next; 286 } *penlist[sizeof(keylist) - 1][2]; 287 288 #define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */ 289 290 /* 291 * Add a penalty for the number `value' to the list for operation `op', 292 * operand number `operand' (0 or 1). If we run out of memory, we just 293 * forget about the penalty (how likely is this, anyway?). 294 */ 295 void 296 penalise(int value, int op, int operand) 297 { 298 struct penalty *p; 299 300 op = opnum(op); 301 if ((p = malloc(sizeof(*p))) == NULL) 302 return; 303 p->next = penlist[op][operand]; 304 penlist[op][operand] = p; 305 penalty[op][operand] += p->penalty = WRONGPENALTY; 306 p->value = value; 307 } 308 309 /* 310 * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1) 311 * of operation `op'. The random number we generate is either used directly 312 * as a value, or represents a position in the penalty list. If the latter, 313 * we find the corresponding value and return that, decreasing its penalty. 314 */ 315 int 316 getrandom(int maxval, int op, int operand) 317 { 318 int value; 319 struct penalty **pp, *p; 320 321 op = opnum(op); 322 value = random() % (maxval + penalty[op][operand]); 323 324 /* 325 * 0 to maxval - 1 is a number to be used directly; bigger values 326 * are positions to be located in the penalty list. 327 */ 328 if (value < maxval) 329 return(value); 330 value -= maxval; 331 332 /* 333 * Find the penalty at position `value'; decrement its penalty and 334 * delete it if it reaches 0; return the corresponding value. 335 */ 336 for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) { 337 if (p->penalty > value) { 338 value = p->value; 339 penalty[op][operand]--; 340 if (--(p->penalty) <= 0) { 341 p = p->next; 342 (void)free((char *)*pp); 343 *pp = p; 344 } 345 return(value); 346 } 347 value -= p->penalty; 348 } 349 /* 350 * We can only get here if the value from the penalty[] array doesn't 351 * correspond to the actual sum of penalties in the list. Provide an 352 * obscure message. 353 */ 354 (void)fprintf(stderr, "arithmetic: bug: inconsistent penalties\n"); 355 exit(1); 356 /* NOTREACHED */ 357 } 358 359 /* Return an index for the character op, which is one of [+-x/]. */ 360 int 361 opnum(int op) 362 { 363 char *p; 364 365 if (op == 0 || (p = index(keylist, op)) == NULL) { 366 (void)fprintf(stderr, 367 "arithmetic: bug: op %c not in keylist %s\n", op, keylist); 368 exit(1); 369 } 370 return(p - keylist); 371 } 372 373 /* Print usage message and quit. */ 374 static void 375 usage(void) 376 { 377 (void)fprintf(stderr, "usage: arithmetic [-o +-x/] [-r range]\n"); 378 exit(1); 379 } 380