1 /* $NetBSD: arithmetic.c,v 1.25 2009/08/27 00:21:45 dholland 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 #include <sys/cdefs.h> 36 #ifndef lint 37 __COPYRIGHT("@(#) Copyright (c) 1989, 1993\ 38 The Regents of the University of California. All rights reserved."); 39 #endif /* not lint */ 40 41 #ifndef lint 42 #if 0 43 static char sccsid[] = "@(#)arithmetic.c 8.1 (Berkeley) 5/31/93"; 44 #else 45 __RCSID("$NetBSD: arithmetic.c,v 1.25 2009/08/27 00:21:45 dholland Exp $"); 46 #endif 47 #endif /* not lint */ 48 49 /* 50 * By Eamonn McManus, Trinity College Dublin <emcmanus@cs.tcd.ie>. 51 * 52 * The operation of this program mimics that of the standard Unix game 53 * `arithmetic'. I've made it as close as I could manage without examining 54 * the source code. The principal differences are: 55 * 56 * The method of biasing towards numbers that had wrong answers in the past 57 * is different; original `arithmetic' seems to retain the bias forever, 58 * whereas this program lets the bias gradually decay as it is used. 59 * 60 * Original `arithmetic' delays for some period (3 seconds?) after printing 61 * the score. I saw no reason for this delay, so I scrapped it. 62 * 63 * There is no longer a limitation on the maximum range that can be supplied 64 * to the program. The original program required it to be less than 100. 65 * Anomalous results may occur with this program if ranges big enough to 66 * allow overflow are given. 67 * 68 * I have obviously not attempted to duplicate bugs in the original. It 69 * would go into an infinite loop if invoked as `arithmetic / 0'. It also 70 * did not recognise an EOF in its input, and would continue trying to read 71 * after it. It did not check that the input was a valid number, treating any 72 * garbage as 0. Finally, it did not flush stdout after printing its prompt, 73 * so in the unlikely event that stdout was not a terminal, it would not work 74 * properly. 75 */ 76 77 #include <sys/types.h> 78 #include <err.h> 79 #include <ctype.h> 80 #include <signal.h> 81 #include <stdio.h> 82 #include <stdlib.h> 83 #include <string.h> 84 #include <time.h> 85 #include <unistd.h> 86 87 static int getrandom(int, int, int); 88 static void intr(int) __dead; 89 static int opnum(int); 90 static void penalise(int, int, int); 91 static int problem(void); 92 static void showstats(int); 93 static void usage(void) __dead; 94 95 static const char keylist[] = "+-x/"; 96 static const char defaultkeys[] = "+-"; 97 static const char *keys = defaultkeys; 98 static int nkeys = sizeof(defaultkeys) - 1; 99 static int rangemax = 10; 100 static int nright, nwrong; 101 static time_t qtime; 102 #define NQUESTS 20 103 104 /* 105 * Select keys from +-x/ to be asked addition, subtraction, multiplication, 106 * and division problems. More than one key may be given. The default is 107 * +-. Specify a range to confine the operands to 0 - range. Default upper 108 * bound is 10. After every NQUESTS questions, statistics on the performance 109 * so far are printed. 110 */ 111 int 112 main(int argc, char **argv) 113 { 114 int ch, cnt; 115 116 /* Revoke setgid privileges */ 117 setgid(getgid()); 118 119 while ((ch = getopt(argc, argv, "r:o:")) != -1) 120 switch(ch) { 121 case 'o': { 122 const char *p; 123 124 for (p = keys = optarg; *p; ++p) 125 if (!strchr(keylist, *p)) 126 errx(1, "arithmetic: unknown key."); 127 nkeys = p - optarg; 128 break; 129 } 130 case 'r': 131 if ((rangemax = atoi(optarg)) <= 0) 132 errx(1, "arithmetic: invalid range."); 133 break; 134 case '?': 135 default: 136 usage(); 137 } 138 if (argc -= optind) 139 usage(); 140 141 /* Seed the random-number generator. */ 142 srandom((int)time((time_t *)NULL)); 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(0); 152 } 153 /* NOTREACHED */ 154 } 155 156 /* Handle interrupt character. Print score and exit. */ 157 static void 158 intr(dummy) 159 int dummy __unused; 160 { 161 showstats(1); 162 exit(0); 163 } 164 165 /* Print score. Original `arithmetic' had a delay after printing it. */ 166 static void 167 showstats(bool_sigint) 168 int bool_sigint; 169 { 170 if (nright + nwrong > 0) { 171 (void)printf("\n\nRights %d; Wrongs %d; Score %d%%", 172 nright, nwrong, (int)(100L * nright / (nright + nwrong))); 173 if (nright > 0) 174 (void)printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n", 175 (long)qtime, (float)qtime / nright); 176 } 177 if(!bool_sigint) { 178 (void)printf("Press RETURN to continue...\n"); 179 while(!getchar()) ; 180 } 181 (void)printf("\n"); 182 } 183 184 /* 185 * Pick a problem and ask it. Keeps asking the same problem until supplied 186 * with the correct answer, or until EOF or interrupt is typed. Problems are 187 * selected such that the right operand and either the left operand (for +, x) 188 * or the correct result (for -, /) are in the range 0 to rangemax. Each wrong 189 * answer causes the numbers in the problem to be penalised, so that they are 190 * more likely to appear in subsequent problems. 191 */ 192 static int 193 problem() 194 { 195 char *p; 196 time_t start, finish; 197 int left, op, right, result; 198 char line[80]; 199 200 right = left = result = 0; 201 op = keys[random() % nkeys]; 202 if (op != '/') 203 right = getrandom(rangemax + 1, op, 1); 204 retry: 205 /* Get the operands. */ 206 switch (op) { 207 case '+': 208 left = getrandom(rangemax + 1, op, 0); 209 result = left + right; 210 break; 211 case '-': 212 result = getrandom(rangemax + 1, op, 0); 213 left = right + result; 214 break; 215 case 'x': 216 left = getrandom(rangemax + 1, op, 0); 217 result = left * right; 218 break; 219 case '/': 220 right = getrandom(rangemax, op, 1) + 1; 221 result = getrandom(rangemax + 1, op, 0); 222 left = right * result + random() % right; 223 break; 224 } 225 226 /* 227 * A very big maxrange could cause negative values to pop 228 * up, owing to overflow. 229 */ 230 if (result < 0 || left < 0) 231 goto retry; 232 233 (void)printf("%d %c %d = ", left, op, right); 234 (void)fflush(stdout); 235 (void)time(&start); 236 237 /* 238 * Keep looping until the correct answer is given, or until EOF or 239 * interrupt is typed. 240 */ 241 for (;;) { 242 if (!fgets(line, sizeof(line), stdin)) { 243 (void)printf("\n"); 244 return(EOF); 245 } 246 for (p = line; *p && isspace((unsigned char)*p); ++p); 247 if (!isdigit((unsigned char)*p)) { 248 (void)printf("Please type a number.\n"); 249 continue; 250 } 251 if (atoi(p) == result) { 252 (void)printf("Right!\n"); 253 ++nright; 254 break; 255 } 256 /* Wrong answer; penalise and ask again. */ 257 (void)printf("What?\n"); 258 ++nwrong; 259 penalise(right, op, 1); 260 if (op == 'x' || op == '+') 261 penalise(left, op, 0); 262 else 263 penalise(result, op, 0); 264 } 265 266 /* 267 * Accumulate the time taken. Obviously rounding errors happen here; 268 * however they should cancel out, because some of the time you are 269 * charged for a partially elapsed second at the start, and some of 270 * the time you are not charged for a partially elapsed second at the 271 * end. 272 */ 273 (void)time(&finish); 274 qtime += finish - start; 275 return(0); 276 } 277 278 /* 279 * Here is the code for accumulating penalties against the numbers for which 280 * a wrong answer was given. The right operand and either the left operand 281 * (for +, x) or the result (for -, /) are stored in a list for the particular 282 * operation, and each becomes more likely to appear again in that operation. 283 * Initially, each number is charged a penalty of WRONGPENALTY, giving it that 284 * many extra chances of appearing. Each time it is selected because of this, 285 * its penalty is decreased by one; it is removed when it reaches 0. 286 * 287 * The penalty[] array gives the sum of all penalties in the list for 288 * each operation and each operand. The penlist[] array has the lists of 289 * penalties themselves. 290 */ 291 292 static int penalty[sizeof(keylist) - 1][2]; 293 static struct penalty { 294 int value, penalty; /* Penalised value and its penalty. */ 295 struct penalty *next; 296 } *penlist[sizeof(keylist) - 1][2]; 297 298 #define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */ 299 300 /* 301 * Add a penalty for the number `value' to the list for operation `op', 302 * operand number `operand' (0 or 1). If we run out of memory, we just 303 * forget about the penalty (how likely is this, anyway?). 304 */ 305 static void 306 penalise(value, op, operand) 307 int value, op, operand; 308 { 309 struct penalty *p; 310 311 op = opnum(op); 312 if ((p = malloc(sizeof(*p))) == NULL) 313 return; 314 p->next = penlist[op][operand]; 315 penlist[op][operand] = p; 316 penalty[op][operand] += p->penalty = WRONGPENALTY; 317 p->value = value; 318 } 319 320 /* 321 * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1) 322 * of operation `op'. The random number we generate is either used directly 323 * as a value, or represents a position in the penalty list. If the latter, 324 * we find the corresponding value and return that, decreasing its penalty. 325 */ 326 static int 327 getrandom(maxval, op, operand) 328 int maxval, op, operand; 329 { 330 int value; 331 struct penalty **pp, *p; 332 333 op = opnum(op); 334 value = random() % (maxval + penalty[op][operand]); 335 336 /* 337 * 0 to maxval - 1 is a number to be used directly; bigger values 338 * are positions to be located in the penalty list. 339 */ 340 if (value < maxval) 341 return(value); 342 value -= maxval; 343 344 /* 345 * Find the penalty at position `value'; decrement its penalty and 346 * delete it if it reaches 0; return the corresponding value. 347 */ 348 for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) { 349 if (p->penalty > value) { 350 value = p->value; 351 penalty[op][operand]--; 352 if (--(p->penalty) <= 0) { 353 p = p->next; 354 (void)free((char *)*pp); 355 *pp = p; 356 } 357 return(value); 358 } 359 value -= p->penalty; 360 } 361 /* 362 * We can only get here if the value from the penalty[] array doesn't 363 * correspond to the actual sum of penalties in the list. Provide an 364 * obscure message. 365 */ 366 errx(1, "arithmetic: bug: inconsistent penalties."); 367 /* NOTREACHED */ 368 } 369 370 /* Return an index for the character op, which is one of [+-x/]. */ 371 static int 372 opnum(op) 373 int op; 374 { 375 char *p; 376 377 if (op == 0 || (p = strchr(keylist, op)) == NULL) 378 errx(1, "arithmetic: bug: op %c not in keylist %s", 379 op, keylist); 380 return(p - keylist); 381 } 382 383 /* Print usage message and quit. */ 384 static void 385 usage() 386 { 387 (void)fprintf(stderr, "Usage: %s [-o +-x/] [-r range]\n", 388 getprogname()); 389 exit(1); 390 } 391