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 } 384