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 1.3 2003/11/12 14:53:52 eirikn 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(argc, argv) 105 int argc; 106 char **argv; 107 { 108 int ch, cnt; 109 110 /* Revoke setgid privileges */ 111 setgid(getgid()); 112 113 while ((ch = getopt(argc, argv, "r:o:")) != -1) 114 switch(ch) { 115 case 'o': { 116 const char *p; 117 118 for (p = keys = optarg; *p; ++p) 119 if (!index(keylist, *p)) { 120 (void)fprintf(stderr, 121 "arithmetic: unknown key.\n"); 122 exit(1); 123 } 124 nkeys = p - optarg; 125 break; 126 } 127 case 'r': 128 if ((rangemax = atoi(optarg)) <= 0) { 129 (void)fprintf(stderr, 130 "arithmetic: invalid range.\n"); 131 exit(1); 132 } 133 break; 134 case '?': 135 default: 136 usage(); 137 } 138 if (argc -= optind) 139 usage(); 140 141 /* Seed the random-number generator. */ 142 srandomdev(); 143 144 (void)signal(SIGINT, intr); 145 146 /* Now ask the questions. */ 147 for (;;) { 148 for (cnt = NQUESTS; cnt--;) 149 if (problem() == EOF) 150 exit(0); 151 showstats(); 152 } 153 /* NOTREACHED */ 154 } 155 156 /* Handle interrupt character. Print score and exit. */ 157 void 158 intr(sig) 159 int sig; 160 { 161 showstats(); 162 exit(0); 163 } 164 165 /* Print score. Original `arithmetic' had a delay after printing it. */ 166 void 167 showstats() 168 { 169 if (nright + nwrong > 0) { 170 (void)printf("\n\nRights %d; Wrongs %d; Score %d%%", 171 nright, nwrong, (int)(100L * nright / (nright + nwrong))); 172 if (nright > 0) 173 (void)printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n", 174 (long)qtime, (float)qtime / nright); 175 } 176 (void)printf("\n"); 177 } 178 179 /* 180 * Pick a problem and ask it. Keeps asking the same problem until supplied 181 * with the correct answer, or until EOF or interrupt is typed. Problems are 182 * selected such that the right operand and either the left operand (for +, x) 183 * or the correct result (for -, /) are in the range 0 to rangemax. Each wrong 184 * answer causes the numbers in the problem to be penalised, so that they are 185 * more likely to appear in subsequent problems. 186 */ 187 int 188 problem() 189 { 190 char *p; 191 time_t start, finish; 192 int left, op, right, result; 193 char line[80]; 194 195 left = 0; 196 right = 0; 197 result = 0; 198 op = keys[random() % nkeys]; 199 if (op != '/') 200 right = getrandom(rangemax + 1, op, 1); 201 retry: 202 /* Get the operands. */ 203 switch (op) { 204 case '+': 205 left = getrandom(rangemax + 1, op, 0); 206 result = left + right; 207 break; 208 case '-': 209 result = getrandom(rangemax + 1, op, 0); 210 left = right + result; 211 break; 212 case 'x': 213 left = getrandom(rangemax + 1, op, 0); 214 result = left * right; 215 break; 216 case '/': 217 right = getrandom(rangemax, op, 1) + 1; 218 result = getrandom(rangemax + 1, op, 0); 219 left = right * result + random() % right; 220 break; 221 } 222 223 /* 224 * A very big maxrange could cause negative values to pop 225 * up, owing to overflow. 226 */ 227 if (result < 0 || left < 0) 228 goto retry; 229 230 (void)printf("%d %c %d = ", left, op, right); 231 (void)fflush(stdout); 232 (void)time(&start); 233 234 /* 235 * Keep looping until the correct answer is given, or until EOF or 236 * interrupt is typed. 237 */ 238 for (;;) { 239 if (!fgets(line, sizeof(line), stdin)) { 240 (void)printf("\n"); 241 return(EOF); 242 } 243 for (p = line; *p && isspace(*p); ++p); 244 if (!isdigit(*p)) { 245 (void)printf("Please type a number.\n"); 246 continue; 247 } 248 if (atoi(p) == result) { 249 (void)printf("Right!\n"); 250 ++nright; 251 break; 252 } 253 /* Wrong answer; penalise and ask again. */ 254 (void)printf("What?\n"); 255 ++nwrong; 256 penalise(right, op, 1); 257 if (op == 'x' || op == '+') 258 penalise(left, op, 0); 259 else 260 penalise(result, op, 0); 261 } 262 263 /* 264 * Accumulate the time taken. Obviously rounding errors happen here; 265 * however they should cancel out, because some of the time you are 266 * charged for a partially elapsed second at the start, and some of 267 * the time you are not charged for a partially elapsed second at the 268 * end. 269 */ 270 (void)time(&finish); 271 qtime += finish - start; 272 return(0); 273 } 274 275 /* 276 * Here is the code for accumulating penalties against the numbers for which 277 * a wrong answer was given. The right operand and either the left operand 278 * (for +, x) or the result (for -, /) are stored in a list for the particular 279 * operation, and each becomes more likely to appear again in that operation. 280 * Initially, each number is charged a penalty of WRONGPENALTY, giving it that 281 * many extra chances of appearing. Each time it is selected because of this, 282 * its penalty is decreased by one; it is removed when it reaches 0. 283 * 284 * The penalty[] array gives the sum of all penalties in the list for 285 * each operation and each operand. The penlist[] array has the lists of 286 * penalties themselves. 287 */ 288 289 int penalty[sizeof(keylist) - 1][2]; 290 struct penalty { 291 int value, penalty; /* Penalised value and its penalty. */ 292 struct penalty *next; 293 } *penlist[sizeof(keylist) - 1][2]; 294 295 #define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */ 296 297 /* 298 * Add a penalty for the number `value' to the list for operation `op', 299 * operand number `operand' (0 or 1). If we run out of memory, we just 300 * forget about the penalty (how likely is this, anyway?). 301 */ 302 void 303 penalise(value, op, operand) 304 int value, op, operand; 305 { 306 struct penalty *p; 307 308 op = opnum(op); 309 if ((p = (struct penalty *)malloc((u_int)sizeof(*p))) == NULL) 310 return; 311 p->next = penlist[op][operand]; 312 penlist[op][operand] = p; 313 penalty[op][operand] += p->penalty = WRONGPENALTY; 314 p->value = value; 315 } 316 317 /* 318 * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1) 319 * of operation `op'. The random number we generate is either used directly 320 * as a value, or represents a position in the penalty list. If the latter, 321 * we find the corresponding value and return that, decreasing its penalty. 322 */ 323 int 324 getrandom(maxval, op, operand) 325 int maxval, op, operand; 326 { 327 int value; 328 struct penalty **pp, *p; 329 330 op = opnum(op); 331 value = random() % (maxval + penalty[op][operand]); 332 333 /* 334 * 0 to maxval - 1 is a number to be used directly; bigger values 335 * are positions to be located in the penalty list. 336 */ 337 if (value < maxval) 338 return(value); 339 value -= maxval; 340 341 /* 342 * Find the penalty at position `value'; decrement its penalty and 343 * delete it if it reaches 0; return the corresponding value. 344 */ 345 for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) { 346 if (p->penalty > value) { 347 value = p->value; 348 penalty[op][operand]--; 349 if (--(p->penalty) <= 0) { 350 p = p->next; 351 (void)free((char *)*pp); 352 *pp = p; 353 } 354 return(value); 355 } 356 value -= p->penalty; 357 } 358 /* 359 * We can only get here if the value from the penalty[] array doesn't 360 * correspond to the actual sum of penalties in the list. Provide an 361 * obscure message. 362 */ 363 (void)fprintf(stderr, "arithmetic: bug: inconsistent penalties\n"); 364 exit(1); 365 /* NOTREACHED */ 366 } 367 368 /* Return an index for the character op, which is one of [+-x/]. */ 369 int 370 opnum(op) 371 int op; 372 { 373 char *p; 374 375 if (op == 0 || (p = index(keylist, op)) == NULL) { 376 (void)fprintf(stderr, 377 "arithmetic: bug: op %c not in keylist %s\n", op, keylist); 378 exit(1); 379 } 380 return(p - keylist); 381 } 382 383 /* Print usage message and quit. */ 384 static void 385 usage() 386 { 387 (void)fprintf(stderr, "usage: arithmetic [-o +-x/] [-r range]\n"); 388 exit(1); 389 } 390