1 /* $OpenBSD: arithmetic.c,v 1.16 2007/03/20 03:43:50 tedu 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 #ifndef lint 36 static char copyright[] = 37 "@(#) Copyright (c) 1989, 1993\n\ 38 The Regents of the University of California. All rights reserved.\n"; 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 static char rcsid[] = "$OpenBSD: arithmetic.c,v 1.16 2007/03/20 03:43:50 tedu 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 int getrandom(int, int, int); 88 void intr(int); 89 int opnum(int); 90 void penalise(int, int, int); 91 int problem(void); 92 void showstats(void); 93 void usage(void); 94 95 const char keylist[] = "+-x/"; 96 const char defaultkeys[] = "+-"; 97 const char *keys = defaultkeys; 98 int nkeys = sizeof(defaultkeys) - 1; 99 int rangemax = 10; 100 int nright, nwrong; 101 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 extern char *optarg; 115 extern int optind; 116 int ch, cnt; 117 118 while ((ch = getopt(argc, argv, "hr:o:")) != -1) 119 switch(ch) { 120 case 'o': { 121 const char *p; 122 123 for (p = keys = optarg; *p; ++p) 124 if (!strchr(keylist, *p)) 125 errx(1, "unknown key."); 126 nkeys = p - optarg; 127 break; 128 } 129 case 'r': 130 if ((rangemax = atoi(optarg)) <= 0) 131 errx(1, "invalid range."); 132 break; 133 case '?': 134 case 'h': 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 intr(0); /* Print score and exit */ 151 showstats(); 152 } 153 /* NOTREACHED */ 154 } 155 156 /* Handle interrupt character. Print score and exit. */ 157 void 158 intr(int dummy) 159 { 160 showstats(); 161 exit(0); 162 } 163 164 /* Print score. Original `arithmetic' had a delay after printing it. */ 165 void 166 showstats(void) 167 { 168 if (nright + nwrong > 0) { 169 (void)printf("\n\nRights %d; Wrongs %d; Score %d%%", 170 nright, nwrong, (int)(100L * nright / (nright + nwrong))); 171 if (nright > 0) 172 (void)printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n", 173 (long)qtime, (float)qtime / nright); 174 } 175 (void)printf("\n"); 176 } 177 178 /* 179 * Pick a problem and ask it. Keeps asking the same problem until supplied 180 * with the correct answer, or until EOF or interrupt is typed. Problems are 181 * selected such that the right operand and either the left operand (for +, x) 182 * or the correct result (for -, /) are in the range 0 to rangemax. Each wrong 183 * answer causes the numbers in the problem to be penalised, so that they are 184 * more likely to appear in subsequent problems. 185 */ 186 int 187 problem(void) 188 { 189 char *p; 190 time_t start, finish; 191 int left, op, right, result; 192 char line[80]; 193 194 op = keys[random() % nkeys]; 195 if (op != '/') 196 right = getrandom(rangemax + 1, op, 1); 197 retry: 198 /* Get the operands. */ 199 switch (op) { 200 case '+': 201 left = getrandom(rangemax + 1, op, 0); 202 result = left + right; 203 break; 204 case '-': 205 result = getrandom(rangemax + 1, op, 0); 206 left = right + result; 207 break; 208 case 'x': 209 left = getrandom(rangemax + 1, op, 0); 210 result = left * right; 211 break; 212 case '/': 213 right = getrandom(rangemax, op, 1) + 1; 214 result = getrandom(rangemax + 1, op, 0); 215 left = right * result + random() % right; 216 break; 217 } 218 219 /* 220 * A very big maxrange could cause negative values to pop 221 * up, owing to overflow. 222 */ 223 if (result < 0 || left < 0) 224 goto retry; 225 226 (void)printf("%d %c %d = ", left, op, right); 227 (void)fflush(stdout); 228 (void)time(&start); 229 230 /* 231 * Keep looping until the correct answer is given, or until EOF or 232 * interrupt is typed. 233 */ 234 for (;;) { 235 if (!fgets(line, sizeof(line), stdin)) { 236 (void)printf("\n"); 237 return(EOF); 238 } 239 for (p = line; isspace(*p); ++p); 240 if (!isdigit(*p)) { 241 (void)printf("Please type a number.\n"); 242 continue; 243 } 244 if (atoi(p) == result) { 245 (void)printf("Right!\n"); 246 ++nright; 247 break; 248 } 249 /* Wrong answer; penalise and ask again. */ 250 (void)printf("What?\n"); 251 ++nwrong; 252 penalise(right, op, 1); 253 if (op == 'x' || op == '+') 254 penalise(left, op, 0); 255 else 256 penalise(result, op, 0); 257 } 258 259 /* 260 * Accumulate the time taken. Obviously rounding errors happen here; 261 * however they should cancel out, because some of the time you are 262 * charged for a partially elapsed second at the start, and some of 263 * the time you are not charged for a partially elapsed second at the 264 * end. 265 */ 266 (void)time(&finish); 267 qtime += finish - start; 268 return(0); 269 } 270 271 /* 272 * Here is the code for accumulating penalties against the numbers for which 273 * a wrong answer was given. The right operand and either the left operand 274 * (for +, x) or the result (for -, /) are stored in a list for the particular 275 * operation, and each becomes more likely to appear again in that operation. 276 * Initially, each number is charged a penalty of WRONGPENALTY, giving it that 277 * many extra chances of appearing. Each time it is selected because of this, 278 * its penalty is decreased by one; it is removed when it reaches 0. 279 * 280 * The penalty[] array gives the sum of all penalties in the list for 281 * each operation and each operand. The penlist[] array has the lists of 282 * penalties themselves. 283 */ 284 285 int penalty[sizeof(keylist) - 1][2]; 286 struct penalty { 287 int value, penalty; /* Penalised value and its penalty. */ 288 struct penalty *next; 289 } *penlist[sizeof(keylist) - 1][2]; 290 291 #define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */ 292 293 /* 294 * Add a penalty for the number `value' to the list for operation `op', 295 * operand number `operand' (0 or 1). If we run out of memory, we just 296 * forget about the penalty (how likely is this, anyway?). 297 */ 298 void 299 penalise(int value, int op, int operand) 300 { 301 struct penalty *p; 302 303 op = opnum(op); 304 if ((p = (struct penalty *)malloc((u_int)sizeof(*p))) == NULL) 305 return; 306 p->next = penlist[op][operand]; 307 penlist[op][operand] = p; 308 penalty[op][operand] += p->penalty = WRONGPENALTY; 309 p->value = value; 310 } 311 312 /* 313 * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1) 314 * of operation `op'. The random number we generate is either used directly 315 * as a value, or represents a position in the penalty list. If the latter, 316 * we find the corresponding value and return that, decreasing its penalty. 317 */ 318 int 319 getrandom(int maxval, int op, int operand) 320 { 321 int value; 322 struct penalty **pp, *p; 323 324 op = opnum(op); 325 value = random() % (maxval + penalty[op][operand]); 326 327 /* 328 * 0 to maxval - 1 is a number to be used directly; bigger values 329 * are positions to be located in the penalty list. 330 */ 331 if (value < maxval) 332 return(value); 333 value -= maxval; 334 335 /* 336 * Find the penalty at position `value'; decrement its penalty and 337 * delete it if it reaches 0; return the corresponding value. 338 */ 339 for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) { 340 if (p->penalty > value) { 341 value = p->value; 342 penalty[op][operand]--; 343 if (--(p->penalty) <= 0) { 344 p = p->next; 345 (void)free((char *)*pp); 346 *pp = p; 347 } 348 return(value); 349 } 350 value -= p->penalty; 351 } 352 /* 353 * We can only get here if the value from the penalty[] array doesn't 354 * correspond to the actual sum of penalties in the list. Provide an 355 * obscure message. 356 */ 357 errx(1, "bug: inconsistent penalties."); 358 /* NOTREACHED */ 359 } 360 361 /* Return an index for the character op, which is one of [+-x/]. */ 362 int 363 opnum(int op) 364 { 365 char *p; 366 367 if (op == 0 || (p = strchr(keylist, op)) == NULL) 368 errx(1, "bug: op %c not in keylist %s.", op, keylist); 369 return(p - keylist); 370 } 371 372 /* Print usage message and quit. */ 373 void 374 usage(void) 375 { 376 (void)fprintf(stderr, "usage: arithmetic [-o +-x/] [-r range]\n"); 377 exit(1); 378 } 379