1 /* $NetBSD: arithmetic.c,v 1.17 2001/02/19 22:41:45 cgd 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. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 #include <sys/cdefs.h> 40 #ifndef lint 41 __COPYRIGHT("@(#) Copyright (c) 1989, 1993\n\ 42 The Regents of the University of California. All rights reserved.\n"); 43 #endif /* not lint */ 44 45 #ifndef lint 46 #if 0 47 static char sccsid[] = "@(#)arithmetic.c 8.1 (Berkeley) 5/31/93"; 48 #else 49 __RCSID("$NetBSD: arithmetic.c,v 1.17 2001/02/19 22:41:45 cgd Exp $"); 50 #endif 51 #endif /* not lint */ 52 53 /* 54 * By Eamonn McManus, Trinity College Dublin <emcmanus@cs.tcd.ie>. 55 * 56 * The operation of this program mimics that of the standard Unix game 57 * `arithmetic'. I've made it as close as I could manage without examining 58 * the source code. The principal differences are: 59 * 60 * The method of biasing towards numbers that had wrong answers in the past 61 * is different; original `arithmetic' seems to retain the bias forever, 62 * whereas this program lets the bias gradually decay as it is used. 63 * 64 * Original `arithmetic' delays for some period (3 seconds?) after printing 65 * the score. I saw no reason for this delay, so I scrapped it. 66 * 67 * There is no longer a limitation on the maximum range that can be supplied 68 * to the program. The original program required it to be less than 100. 69 * Anomalous results may occur with this program if ranges big enough to 70 * allow overflow are given. 71 * 72 * I have obviously not attempted to duplicate bugs in the original. It 73 * would go into an infinite loop if invoked as `arithmetic / 0'. It also 74 * did not recognise an EOF in its input, and would continue trying to read 75 * after it. It did not check that the input was a valid number, treating any 76 * garbage as 0. Finally, it did not flush stdout after printing its prompt, 77 * so in the unlikely event that stdout was not a terminal, it would not work 78 * properly. 79 */ 80 81 #include <sys/types.h> 82 #include <err.h> 83 #include <ctype.h> 84 #include <signal.h> 85 #include <stdio.h> 86 #include <stdlib.h> 87 #include <string.h> 88 #include <time.h> 89 #include <unistd.h> 90 91 int getrandom __P((int, int, int)); 92 void intr __P((int)) __attribute__((__noreturn__)); 93 int main __P((int, char *[])); 94 int opnum __P((int)); 95 void penalise __P((int, int, int)); 96 int problem __P((void)); 97 void showstats __P((void)); 98 void usage __P((void)) __attribute__((__noreturn__)); 99 100 const char keylist[] = "+-x/"; 101 const char defaultkeys[] = "+-"; 102 const char *keys = defaultkeys; 103 int nkeys = sizeof(defaultkeys) - 1; 104 int rangemax = 10; 105 int nright, nwrong; 106 time_t qtime; 107 #define NQUESTS 20 108 109 /* 110 * Select keys from +-x/ to be asked addition, subtraction, multiplication, 111 * and division problems. More than one key may be given. The default is 112 * +-. Specify a range to confine the operands to 0 - range. Default upper 113 * bound is 10. After every NQUESTS questions, statistics on the performance 114 * so far are printed. 115 */ 116 int 117 main(argc, argv) 118 int argc; 119 char **argv; 120 { 121 int ch, cnt; 122 123 /* Revoke setgid privileges */ 124 setgid(getgid()); 125 126 while ((ch = getopt(argc, argv, "r:o:")) != -1) 127 switch(ch) { 128 case 'o': { 129 const char *p; 130 131 for (p = keys = optarg; *p; ++p) 132 if (!strchr(keylist, *p)) 133 errx(1, "arithmetic: unknown key."); 134 nkeys = p - optarg; 135 break; 136 } 137 case 'r': 138 if ((rangemax = atoi(optarg)) <= 0) 139 errx(1, "arithmetic: invalid range."); 140 break; 141 case '?': 142 default: 143 usage(); 144 } 145 if (argc -= optind) 146 usage(); 147 148 /* Seed the random-number generator. */ 149 srandom((int)time((time_t *)NULL)); 150 151 (void)signal(SIGINT, intr); 152 153 /* Now ask the questions. */ 154 for (;;) { 155 for (cnt = NQUESTS; cnt--;) 156 if (problem() == EOF) 157 exit(0); 158 showstats(); 159 } 160 /* NOTREACHED */ 161 } 162 163 /* Handle interrupt character. Print score and exit. */ 164 void 165 intr(dummy) 166 int dummy __attribute__((__unused__)); 167 { 168 showstats(); 169 exit(0); 170 } 171 172 /* Print score. Original `arithmetic' had a delay after printing it. */ 173 void 174 showstats() 175 { 176 if (nright + nwrong > 0) { 177 (void)printf("\n\nRights %d; Wrongs %d; Score %d%%", 178 nright, nwrong, (int)(100L * nright / (nright + nwrong))); 179 if (nright > 0) 180 (void)printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n", 181 (long)qtime, (float)qtime / nright); 182 } 183 (void)printf("\n"); 184 } 185 186 /* 187 * Pick a problem and ask it. Keeps asking the same problem until supplied 188 * with the correct answer, or until EOF or interrupt is typed. Problems are 189 * selected such that the right operand and either the left operand (for +, x) 190 * or the correct result (for -, /) are in the range 0 to rangemax. Each wrong 191 * answer causes the numbers in the problem to be penalised, so that they are 192 * more likely to appear in subsequent problems. 193 */ 194 int 195 problem() 196 { 197 char *p; 198 time_t start, finish; 199 int left, op, right, result; 200 char line[80]; 201 202 right = left = result = 0; 203 op = keys[random() % nkeys]; 204 if (op != '/') 205 right = getrandom(rangemax + 1, op, 1); 206 retry: 207 /* Get the operands. */ 208 switch (op) { 209 case '+': 210 left = getrandom(rangemax + 1, op, 0); 211 result = left + right; 212 break; 213 case '-': 214 result = getrandom(rangemax + 1, op, 0); 215 left = right + result; 216 break; 217 case 'x': 218 left = getrandom(rangemax + 1, op, 0); 219 result = left * right; 220 break; 221 case '/': 222 right = getrandom(rangemax, op, 1) + 1; 223 result = getrandom(rangemax + 1, op, 0); 224 left = right * result + random() % right; 225 break; 226 } 227 228 /* 229 * A very big maxrange could cause negative values to pop 230 * up, owing to overflow. 231 */ 232 if (result < 0 || left < 0) 233 goto retry; 234 235 (void)printf("%d %c %d = ", left, op, right); 236 (void)fflush(stdout); 237 (void)time(&start); 238 239 /* 240 * Keep looping until the correct answer is given, or until EOF or 241 * interrupt is typed. 242 */ 243 for (;;) { 244 if (!fgets(line, sizeof(line), stdin)) { 245 (void)printf("\n"); 246 return(EOF); 247 } 248 for (p = line; *p && isspace(*p); ++p); 249 if (!isdigit(*p)) { 250 (void)printf("Please type a number.\n"); 251 continue; 252 } 253 if (atoi(p) == result) { 254 (void)printf("Right!\n"); 255 ++nright; 256 break; 257 } 258 /* Wrong answer; penalise and ask again. */ 259 (void)printf("What?\n"); 260 ++nwrong; 261 penalise(right, op, 1); 262 if (op == 'x' || op == '+') 263 penalise(left, op, 0); 264 else 265 penalise(result, op, 0); 266 } 267 268 /* 269 * Accumulate the time taken. Obviously rounding errors happen here; 270 * however they should cancel out, because some of the time you are 271 * charged for a partially elapsed second at the start, and some of 272 * the time you are not charged for a partially elapsed second at the 273 * end. 274 */ 275 (void)time(&finish); 276 qtime += finish - start; 277 return(0); 278 } 279 280 /* 281 * Here is the code for accumulating penalties against the numbers for which 282 * a wrong answer was given. The right operand and either the left operand 283 * (for +, x) or the result (for -, /) are stored in a list for the particular 284 * operation, and each becomes more likely to appear again in that operation. 285 * Initially, each number is charged a penalty of WRONGPENALTY, giving it that 286 * many extra chances of appearing. Each time it is selected because of this, 287 * its penalty is decreased by one; it is removed when it reaches 0. 288 * 289 * The penalty[] array gives the sum of all penalties in the list for 290 * each operation and each operand. The penlist[] array has the lists of 291 * penalties themselves. 292 */ 293 294 int penalty[sizeof(keylist) - 1][2]; 295 struct penalty { 296 int value, penalty; /* Penalised value and its penalty. */ 297 struct penalty *next; 298 } *penlist[sizeof(keylist) - 1][2]; 299 300 #define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */ 301 302 /* 303 * Add a penalty for the number `value' to the list for operation `op', 304 * operand number `operand' (0 or 1). If we run out of memory, we just 305 * forget about the penalty (how likely is this, anyway?). 306 */ 307 void 308 penalise(value, op, operand) 309 int value, op, operand; 310 { 311 struct penalty *p; 312 313 op = opnum(op); 314 if ((p = (struct penalty *)malloc((u_int)sizeof(*p))) == NULL) 315 return; 316 p->next = penlist[op][operand]; 317 penlist[op][operand] = p; 318 penalty[op][operand] += p->penalty = WRONGPENALTY; 319 p->value = value; 320 } 321 322 /* 323 * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1) 324 * of operation `op'. The random number we generate is either used directly 325 * as a value, or represents a position in the penalty list. If the latter, 326 * we find the corresponding value and return that, decreasing its penalty. 327 */ 328 int 329 getrandom(maxval, op, operand) 330 int maxval, op, operand; 331 { 332 int value; 333 struct penalty **pp, *p; 334 335 op = opnum(op); 336 value = random() % (maxval + penalty[op][operand]); 337 338 /* 339 * 0 to maxval - 1 is a number to be used directly; bigger values 340 * are positions to be located in the penalty list. 341 */ 342 if (value < maxval) 343 return(value); 344 value -= maxval; 345 346 /* 347 * Find the penalty at position `value'; decrement its penalty and 348 * delete it if it reaches 0; return the corresponding value. 349 */ 350 for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) { 351 if (p->penalty > value) { 352 value = p->value; 353 penalty[op][operand]--; 354 if (--(p->penalty) <= 0) { 355 p = p->next; 356 (void)free((char *)*pp); 357 *pp = p; 358 } 359 return(value); 360 } 361 value -= p->penalty; 362 } 363 /* 364 * We can only get here if the value from the penalty[] array doesn't 365 * correspond to the actual sum of penalties in the list. Provide an 366 * obscure message. 367 */ 368 errx(1, "arithmetic: bug: inconsistent penalties."); 369 /* NOTREACHED */ 370 } 371 372 /* Return an index for the character op, which is one of [+-x/]. */ 373 int 374 opnum(op) 375 int op; 376 { 377 char *p; 378 379 if (op == 0 || (p = strchr(keylist, op)) == NULL) 380 errx(1, "arithmetic: bug: op %c not in keylist %s", 381 op, keylist); 382 return(p - keylist); 383 } 384 385 /* Print usage message and quit. */ 386 void 387 usage() 388 { 389 (void)fprintf(stderr, "Usage: %s [-o +-x/] [-r range]\n", 390 getprogname()); 391 exit(1); 392 } 393