1 /* $NetBSD: arithmetic.c,v 1.6 1996/03/21 18:30:19 jtc 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 #ifndef lint 40 static char copyright[] = 41 "@(#) 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 static char rcsid[] = "$NetBSD: arithmetic.c,v 1.6 1996/03/21 18:30:19 jtc 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 <signal.h> 83 #include <ctype.h> 84 #include <stdio.h> 85 #include <string.h> 86 #include <time.h> 87 88 char keylist[] = "+-x/"; 89 char defaultkeys[] = "+-"; 90 char *keys = defaultkeys; 91 int nkeys = sizeof(defaultkeys) - 1; 92 int rangemax = 10; 93 int nright, nwrong; 94 time_t qtime; 95 #define NQUESTS 20 96 97 /* 98 * Select keys from +-x/ to be asked addition, subtraction, multiplication, 99 * and division problems. More than one key may be given. The default is 100 * +-. Specify a range to confine the operands to 0 - range. Default upper 101 * bound is 10. After every NQUESTS questions, statistics on the performance 102 * so far are printed. 103 */ 104 int 105 main(argc, argv) 106 int argc; 107 char **argv; 108 { 109 extern char *optarg; 110 extern int optind; 111 int ch, cnt; 112 void intr(); 113 114 while ((ch = getopt(argc, argv, "r:o:")) != EOF) 115 switch(ch) { 116 case 'o': { 117 register char *p; 118 119 for (p = keys = optarg; *p; ++p) 120 if (!index(keylist, *p)) { 121 (void)fprintf(stderr, 122 "arithmetic: unknown key.\n"); 123 exit(1); 124 } 125 nkeys = p - optarg; 126 break; 127 } 128 case 'r': 129 if ((rangemax = atoi(optarg)) <= 0) { 130 (void)fprintf(stderr, 131 "arithmetic: invalid range.\n"); 132 exit(1); 133 } 134 break; 135 case '?': 136 default: 137 usage(); 138 } 139 if (argc -= optind) 140 usage(); 141 142 /* Seed the random-number generator. */ 143 srandom((int)time((time_t *)NULL)); 144 145 (void)signal(SIGINT, intr); 146 147 /* Now ask the questions. */ 148 for (;;) { 149 for (cnt = NQUESTS; cnt--;) 150 if (problem() == EOF) 151 exit(0); 152 showstats(); 153 } 154 /* NOTREACHED */ 155 } 156 157 /* Handle interrupt character. Print score and exit. */ 158 void 159 intr() 160 { 161 showstats(); 162 exit(0); 163 } 164 165 /* Print score. Original `arithmetic' had a delay after printing it. */ 166 showstats() 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 problem() 187 { 188 register char *p; 189 time_t start, finish; 190 int left, op, right, result; 191 char line[80]; 192 193 op = keys[random() % nkeys]; 194 if (op != '/') 195 right = getrandom(rangemax + 1, op, 1); 196 retry: 197 /* Get the operands. */ 198 switch (op) { 199 case '+': 200 left = getrandom(rangemax + 1, op, 0); 201 result = left + right; 202 break; 203 case '-': 204 result = getrandom(rangemax + 1, op, 0); 205 left = right + result; 206 break; 207 case 'x': 208 left = getrandom(rangemax + 1, op, 0); 209 result = left * right; 210 break; 211 case '/': 212 right = getrandom(rangemax, op, 1) + 1; 213 result = getrandom(rangemax + 1, op, 0); 214 left = right * result + random() % right; 215 break; 216 } 217 218 /* 219 * A very big maxrange could cause negative values to pop 220 * up, owing to overflow. 221 */ 222 if (result < 0 || left < 0) 223 goto retry; 224 225 (void)printf("%d %c %d = ", left, op, right); 226 (void)fflush(stdout); 227 (void)time(&start); 228 229 /* 230 * Keep looping until the correct answer is given, or until EOF or 231 * interrupt is typed. 232 */ 233 for (;;) { 234 if (!fgets(line, sizeof(line), stdin)) { 235 (void)printf("\n"); 236 return(EOF); 237 } 238 for (p = line; *p && isspace(*p); ++p); 239 if (!isdigit(*p)) { 240 (void)printf("Please type a number.\n"); 241 continue; 242 } 243 if (atoi(p) == result) { 244 (void)printf("Right!\n"); 245 ++nright; 246 break; 247 } 248 /* Wrong answer; penalise and ask again. */ 249 (void)printf("What?\n"); 250 ++nwrong; 251 penalise(right, op, 1); 252 if (op == 'x' || op == '+') 253 penalise(left, op, 0); 254 else 255 penalise(result, op, 0); 256 } 257 258 /* 259 * Accumulate the time taken. Obviously rounding errors happen here; 260 * however they should cancel out, because some of the time you are 261 * charged for a partially elapsed second at the start, and some of 262 * the time you are not charged for a partially elapsed second at the 263 * end. 264 */ 265 (void)time(&finish); 266 qtime += finish - start; 267 return(0); 268 } 269 270 /* 271 * Here is the code for accumulating penalties against the numbers for which 272 * a wrong answer was given. The right operand and either the left operand 273 * (for +, x) or the result (for -, /) are stored in a list for the particular 274 * operation, and each becomes more likely to appear again in that operation. 275 * Initially, each number is charged a penalty of WRONGPENALTY, giving it that 276 * many extra chances of appearing. Each time it is selected because of this, 277 * its penalty is decreased by one; it is removed when it reaches 0. 278 * 279 * The penalty[] array gives the sum of all penalties in the list for 280 * each operation and each operand. The penlist[] array has the lists of 281 * penalties themselves. 282 */ 283 284 int penalty[sizeof(keylist) - 1][2]; 285 struct penalty { 286 int value, penalty; /* Penalised value and its penalty. */ 287 struct penalty *next; 288 } *penlist[sizeof(keylist) - 1][2]; 289 290 #define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */ 291 292 /* 293 * Add a penalty for the number `value' to the list for operation `op', 294 * operand number `operand' (0 or 1). If we run out of memory, we just 295 * forget about the penalty (how likely is this, anyway?). 296 */ 297 penalise(value, op, operand) 298 int value, op, operand; 299 { 300 struct penalty *p; 301 char *malloc(); 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 getrandom(maxval, op, operand) 319 int maxval, op, operand; 320 { 321 int value; 322 register 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 (void)fprintf(stderr, "arithmetic: bug: inconsistent penalties\n"); 358 exit(1); 359 /* NOTREACHED */ 360 } 361 362 /* Return an index for the character op, which is one of [+-x/]. */ 363 opnum(op) 364 int op; 365 { 366 char *p; 367 368 if (op == 0 || (p = index(keylist, op)) == NULL) { 369 (void)fprintf(stderr, 370 "arithmetic: bug: op %c not in keylist %s\n", op, keylist); 371 exit(1); 372 } 373 return(p - keylist); 374 } 375 376 /* Print usage message and quit. */ 377 usage() 378 { 379 (void)fprintf(stderr, "usage: arithmetic [-o +-x/] [-r range]\n"); 380 exit(1); 381 } 382