1 /* $NetBSD: arithmetic.c,v 1.10 1998/02/03 05:33:32 perry 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 1.10 1998/02/03 05:33:32 perry 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)); 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)); 99 100 char keylist[] = "+-x/"; 101 char defaultkeys[] = "+-"; 102 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 extern char *optarg; 122 extern int optind; 123 int ch, cnt; 124 125 while ((ch = getopt(argc, argv, "r:o:")) != -1) 126 switch(ch) { 127 case 'o': { 128 char *p; 129 130 for (p = keys = optarg; *p; ++p) 131 if (!strchr(keylist, *p)) 132 errx(1, "arithmetic: unknown key."); 133 nkeys = p - optarg; 134 break; 135 } 136 case 'r': 137 if ((rangemax = atoi(optarg)) <= 0) 138 errx(1, "arithmetic: invalid range."); 139 break; 140 case '?': 141 default: 142 usage(); 143 } 144 if (argc -= optind) 145 usage(); 146 147 /* Seed the random-number generator. */ 148 srandom((int)time((time_t *)NULL)); 149 150 (void)signal(SIGINT, intr); 151 152 /* Now ask the questions. */ 153 for (;;) { 154 for (cnt = NQUESTS; cnt--;) 155 if (problem() == EOF) 156 exit(0); 157 showstats(); 158 } 159 /* NOTREACHED */ 160 } 161 162 /* Handle interrupt character. Print score and exit. */ 163 void 164 intr(dummy) 165 int dummy; 166 { 167 showstats(); 168 exit(0); 169 } 170 171 /* Print score. Original `arithmetic' had a delay after printing it. */ 172 void 173 showstats() 174 { 175 if (nright + nwrong > 0) { 176 (void)printf("\n\nRights %d; Wrongs %d; Score %d%%", 177 nright, nwrong, (int)(100L * nright / (nright + nwrong))); 178 if (nright > 0) 179 (void)printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n", 180 (long)qtime, (float)qtime / nright); 181 } 182 (void)printf("\n"); 183 } 184 185 /* 186 * Pick a problem and ask it. Keeps asking the same problem until supplied 187 * with the correct answer, or until EOF or interrupt is typed. Problems are 188 * selected such that the right operand and either the left operand (for +, x) 189 * or the correct result (for -, /) are in the range 0 to rangemax. Each wrong 190 * answer causes the numbers in the problem to be penalised, so that they are 191 * more likely to appear in subsequent problems. 192 */ 193 int 194 problem() 195 { 196 char *p; 197 time_t start, finish; 198 int left, op, right, result; 199 char line[80]; 200 201 right = left = result = 0; 202 op = keys[random() % nkeys]; 203 if (op != '/') 204 right = getrandom(rangemax + 1, op, 1); 205 retry: 206 /* Get the operands. */ 207 switch (op) { 208 case '+': 209 left = getrandom(rangemax + 1, op, 0); 210 result = left + right; 211 break; 212 case '-': 213 result = getrandom(rangemax + 1, op, 0); 214 left = right + result; 215 break; 216 case 'x': 217 left = getrandom(rangemax + 1, op, 0); 218 result = left * right; 219 break; 220 case '/': 221 right = getrandom(rangemax, op, 1) + 1; 222 result = getrandom(rangemax + 1, op, 0); 223 left = right * result + random() % right; 224 break; 225 } 226 227 /* 228 * A very big maxrange could cause negative values to pop 229 * up, owing to overflow. 230 */ 231 if (result < 0 || left < 0) 232 goto retry; 233 234 (void)printf("%d %c %d = ", left, op, right); 235 (void)fflush(stdout); 236 (void)time(&start); 237 238 /* 239 * Keep looping until the correct answer is given, or until EOF or 240 * interrupt is typed. 241 */ 242 for (;;) { 243 if (!fgets(line, sizeof(line), stdin)) { 244 (void)printf("\n"); 245 return(EOF); 246 } 247 for (p = line; *p && isspace(*p); ++p); 248 if (!isdigit(*p)) { 249 (void)printf("Please type a number.\n"); 250 continue; 251 } 252 if (atoi(p) == result) { 253 (void)printf("Right!\n"); 254 ++nright; 255 break; 256 } 257 /* Wrong answer; penalise and ask again. */ 258 (void)printf("What?\n"); 259 ++nwrong; 260 penalise(right, op, 1); 261 if (op == 'x' || op == '+') 262 penalise(left, op, 0); 263 else 264 penalise(result, op, 0); 265 } 266 267 /* 268 * Accumulate the time taken. Obviously rounding errors happen here; 269 * however they should cancel out, because some of the time you are 270 * charged for a partially elapsed second at the start, and some of 271 * the time you are not charged for a partially elapsed second at the 272 * end. 273 */ 274 (void)time(&finish); 275 qtime += finish - start; 276 return(0); 277 } 278 279 /* 280 * Here is the code for accumulating penalties against the numbers for which 281 * a wrong answer was given. The right operand and either the left operand 282 * (for +, x) or the result (for -, /) are stored in a list for the particular 283 * operation, and each becomes more likely to appear again in that operation. 284 * Initially, each number is charged a penalty of WRONGPENALTY, giving it that 285 * many extra chances of appearing. Each time it is selected because of this, 286 * its penalty is decreased by one; it is removed when it reaches 0. 287 * 288 * The penalty[] array gives the sum of all penalties in the list for 289 * each operation and each operand. The penlist[] array has the lists of 290 * penalties themselves. 291 */ 292 293 int penalty[sizeof(keylist) - 1][2]; 294 struct penalty { 295 int value, penalty; /* Penalised value and its penalty. */ 296 struct penalty *next; 297 } *penlist[sizeof(keylist) - 1][2]; 298 299 #define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */ 300 301 /* 302 * Add a penalty for the number `value' to the list for operation `op', 303 * operand number `operand' (0 or 1). If we run out of memory, we just 304 * forget about the penalty (how likely is this, anyway?). 305 */ 306 void 307 penalise(value, op, operand) 308 int value, op, operand; 309 { 310 struct penalty *p; 311 312 op = opnum(op); 313 if ((p = (struct penalty *)malloc((u_int)sizeof(*p))) == NULL) 314 return; 315 p->next = penlist[op][operand]; 316 penlist[op][operand] = p; 317 penalty[op][operand] += p->penalty = WRONGPENALTY; 318 p->value = value; 319 } 320 321 /* 322 * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1) 323 * of operation `op'. The random number we generate is either used directly 324 * as a value, or represents a position in the penalty list. If the latter, 325 * we find the corresponding value and return that, decreasing its penalty. 326 */ 327 int 328 getrandom(maxval, op, operand) 329 int maxval, op, operand; 330 { 331 int value; 332 struct penalty **pp, *p; 333 334 op = opnum(op); 335 value = random() % (maxval + penalty[op][operand]); 336 337 /* 338 * 0 to maxval - 1 is a number to be used directly; bigger values 339 * are positions to be located in the penalty list. 340 */ 341 if (value < maxval) 342 return(value); 343 value -= maxval; 344 345 /* 346 * Find the penalty at position `value'; decrement its penalty and 347 * delete it if it reaches 0; return the corresponding value. 348 */ 349 for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) { 350 if (p->penalty > value) { 351 value = p->value; 352 penalty[op][operand]--; 353 if (--(p->penalty) <= 0) { 354 p = p->next; 355 (void)free((char *)*pp); 356 *pp = p; 357 } 358 return(value); 359 } 360 value -= p->penalty; 361 } 362 /* 363 * We can only get here if the value from the penalty[] array doesn't 364 * correspond to the actual sum of penalties in the list. Provide an 365 * obscure message. 366 */ 367 errx(1, "arithmetic: bug: inconsistent penalties."); 368 /* NOTREACHED */ 369 } 370 371 /* Return an index for the character op, which is one of [+-x/]. */ 372 int 373 opnum(op) 374 int op; 375 { 376 char *p; 377 378 if (op == 0 || (p = strchr(keylist, op)) == NULL) 379 errx(1, "arithmetic: bug: op %c not in keylist %s", 380 op, keylist); 381 return(p - keylist); 382 } 383 384 /* Print usage message and quit. */ 385 void 386 usage() 387 { 388 extern char *__progname; /* from crt0.o */ 389 390 (void)fprintf(stderr, "usage: %s [-o +-x/] [-r range]\n", 391 __progname); 392 exit(1); 393 } 394