1 /* 2 * Copyright (c) 1989 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Eamonn McManus of Trinity College Dublin. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 #ifndef lint 38 char copyright[] = 39 "@(#) Copyright (c) 1989 The Regents of the University of California.\n\ 40 All rights reserved.\n"; 41 #endif /* not lint */ 42 43 #ifndef lint 44 /*static char sccsid[] = "from: @(#)arithmetic.c 5.5 (Berkeley) 2/27/91";*/ 45 static char rcsid[] = "$Id: arithmetic.c,v 1.3 1993/08/01 18:57:22 mycroft Exp $"; 46 #endif /* not lint */ 47 48 /* 49 * By Eamonn McManus, Trinity College Dublin <emcmanus@cs.tcd.ie>. 50 * 51 * The operation of this program mimics that of the standard Unix game 52 * `arithmetic'. I've made it as close as I could manage without examining 53 * the source code. The principal differences are: 54 * 55 * The method of biasing towards numbers that had wrong answers in the past 56 * is different; original `arithmetic' seems to retain the bias forever, 57 * whereas this program lets the bias gradually decay as it is used. 58 * 59 * Original `arithmetic' delays for some period (3 seconds?) after printing 60 * the score. I saw no reason for this delay, so I scrapped it. 61 * 62 * There is no longer a limitation on the maximum range that can be supplied 63 * to the program. The original program required it to be less than 100. 64 * Anomalous results may occur with this program if ranges big enough to 65 * allow overflow are given. 66 * 67 * I have obviously not attempted to duplicate bugs in the original. It 68 * would go into an infinite loop if invoked as `arithmetic / 0'. It also 69 * did not recognise an EOF in its input, and would continue trying to read 70 * after it. It did not check that the input was a valid number, treating any 71 * garbage as 0. Finally, it did not flush stdout after printing its prompt, 72 * so in the unlikely event that stdout was not a terminal, it would not work 73 * properly. 74 */ 75 76 #include <sys/types.h> 77 #include <sys/signal.h> 78 #include <ctype.h> 79 #include <stdio.h> 80 #include <string.h> 81 #include <time.h> 82 83 char keylist[] = "+-x/"; 84 char defaultkeys[] = "+-"; 85 char *keys = defaultkeys; 86 int nkeys = sizeof(defaultkeys) - 1; 87 int rangemax = 10; 88 int nright, nwrong; 89 time_t qtime; 90 #define NQUESTS 20 91 92 /* 93 * Select keys from +-x/ to be asked addition, subtraction, multiplication, 94 * and division problems. More than one key may be given. The default is 95 * +-. Specify a range to confine the operands to 0 - range. Default upper 96 * bound is 10. After every NQUESTS questions, statistics on the performance 97 * so far are printed. 98 */ 99 void 100 main(argc, argv) 101 int argc; 102 char **argv; 103 { 104 extern char *optarg; 105 extern int optind; 106 int ch, cnt; 107 void intr(); 108 109 while ((ch = getopt(argc, argv, "r:o:")) != EOF) 110 switch(ch) { 111 case 'o': { 112 register char *p; 113 114 for (p = keys = optarg; *p; ++p) 115 if (!index(keylist, *p)) { 116 (void)fprintf(stderr, 117 "arithmetic: unknown key.\n"); 118 exit(1); 119 } 120 nkeys = p - optarg; 121 break; 122 } 123 case 'r': 124 if ((rangemax = atoi(optarg)) <= 0) { 125 (void)fprintf(stderr, 126 "arithmetic: invalid range.\n"); 127 exit(1); 128 } 129 break; 130 case '?': 131 default: 132 usage(); 133 } 134 if (argc -= optind) 135 usage(); 136 137 /* Seed the random-number generator. */ 138 srandom((int)time((time_t *)NULL)); 139 140 (void)signal(SIGINT, intr); 141 142 /* Now ask the questions. */ 143 for (;;) { 144 for (cnt = NQUESTS; cnt--;) 145 if (problem() == EOF) 146 exit(0); 147 showstats(); 148 } 149 /* NOTREACHED */ 150 } 151 152 /* Handle interrupt character. Print score and exit. */ 153 void 154 intr() 155 { 156 showstats(); 157 exit(0); 158 } 159 160 /* Print score. Original `arithmetic' had a delay after printing it. */ 161 showstats() 162 { 163 if (nright + nwrong > 0) { 164 (void)printf("\n\nRights %d; Wrongs %d; Score %d%%", 165 nright, nwrong, (int)(100L * nright / (nright + nwrong))); 166 if (nright > 0) 167 (void)printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n", 168 (long)qtime, (float)qtime / nright); 169 } 170 (void)printf("\n"); 171 } 172 173 /* 174 * Pick a problem and ask it. Keeps asking the same problem until supplied 175 * with the correct answer, or until EOF or interrupt is typed. Problems are 176 * selected such that the right operand and either the left operand (for +, x) 177 * or the correct result (for -, /) are in the range 0 to rangemax. Each wrong 178 * answer causes the numbers in the problem to be penalised, so that they are 179 * more likely to appear in subsequent problems. 180 */ 181 problem() 182 { 183 register char *p; 184 time_t start, finish; 185 int left, op, right, result; 186 char line[80]; 187 188 op = keys[random() % nkeys]; 189 if (op != '/') 190 right = getrandom(rangemax + 1, op, 1); 191 retry: 192 /* Get the operands. */ 193 switch (op) { 194 case '+': 195 left = getrandom(rangemax + 1, op, 0); 196 result = left + right; 197 break; 198 case '-': 199 result = getrandom(rangemax + 1, op, 0); 200 left = right + result; 201 break; 202 case 'x': 203 left = getrandom(rangemax + 1, op, 0); 204 result = left * right; 205 break; 206 case '/': 207 right = getrandom(rangemax, op, 1) + 1; 208 result = getrandom(rangemax + 1, op, 0); 209 left = right * result + random() % right; 210 break; 211 } 212 213 /* 214 * A very big maxrange could cause negative values to pop 215 * up, owing to overflow. 216 */ 217 if (result < 0 || left < 0) 218 goto retry; 219 220 (void)printf("%d %c %d = ", left, op, right); 221 (void)fflush(stdout); 222 (void)time(&start); 223 224 /* 225 * Keep looping until the correct answer is given, or until EOF or 226 * interrupt is typed. 227 */ 228 for (;;) { 229 if (!fgets(line, sizeof(line), stdin)) { 230 (void)printf("\n"); 231 return(EOF); 232 } 233 for (p = line; *p && isspace(*p); ++p); 234 if (!isdigit(*p)) { 235 (void)printf("Please type a number.\n"); 236 continue; 237 } 238 if (atoi(p) == result) { 239 (void)printf("Right!\n"); 240 ++nright; 241 break; 242 } 243 /* Wrong answer; penalise and ask again. */ 244 (void)printf("What?\n"); 245 ++nwrong; 246 penalise(right, op, 1); 247 if (op == 'x' || op == '+') 248 penalise(left, op, 0); 249 else 250 penalise(result, op, 0); 251 } 252 253 /* 254 * Accumulate the time taken. Obviously rounding errors happen here; 255 * however they should cancel out, because some of the time you are 256 * charged for a partially elapsed second at the start, and some of 257 * the time you are not charged for a partially elapsed second at the 258 * end. 259 */ 260 (void)time(&finish); 261 qtime += finish - start; 262 return(0); 263 } 264 265 /* 266 * Here is the code for accumulating penalties against the numbers for which 267 * a wrong answer was given. The right operand and either the left operand 268 * (for +, x) or the result (for -, /) are stored in a list for the particular 269 * operation, and each becomes more likely to appear again in that operation. 270 * Initially, each number is charged a penalty of WRONGPENALTY, giving it that 271 * many extra chances of appearing. Each time it is selected because of this, 272 * its penalty is decreased by one; it is removed when it reaches 0. 273 * 274 * The penalty[] array gives the sum of all penalties in the list for 275 * each operation and each operand. The penlist[] array has the lists of 276 * penalties themselves. 277 */ 278 279 int penalty[sizeof(keylist) - 1][2]; 280 struct penalty { 281 int value, penalty; /* Penalised value and its penalty. */ 282 struct penalty *next; 283 } *penlist[sizeof(keylist) - 1][2]; 284 285 #define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */ 286 287 /* 288 * Add a penalty for the number `value' to the list for operation `op', 289 * operand number `operand' (0 or 1). If we run out of memory, we just 290 * forget about the penalty (how likely is this, anyway?). 291 */ 292 penalise(value, op, operand) 293 int value, op, operand; 294 { 295 struct penalty *p; 296 char *malloc(); 297 298 op = opnum(op); 299 if ((p = (struct penalty *)malloc((u_int)sizeof(*p))) == NULL) 300 return; 301 p->next = penlist[op][operand]; 302 penlist[op][operand] = p; 303 penalty[op][operand] += p->penalty = WRONGPENALTY; 304 p->value = value; 305 } 306 307 /* 308 * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1) 309 * of operation `op'. The random number we generate is either used directly 310 * as a value, or represents a position in the penalty list. If the latter, 311 * we find the corresponding value and return that, decreasing its penalty. 312 */ 313 getrandom(maxval, op, operand) 314 int maxval, op, operand; 315 { 316 int value; 317 register struct penalty **pp, *p; 318 319 op = opnum(op); 320 value = random() % (maxval + penalty[op][operand]); 321 322 /* 323 * 0 to maxval - 1 is a number to be used directly; bigger values 324 * are positions to be located in the penalty list. 325 */ 326 if (value < maxval) 327 return(value); 328 value -= maxval; 329 330 /* 331 * Find the penalty at position `value'; decrement its penalty and 332 * delete it if it reaches 0; return the corresponding value. 333 */ 334 for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) { 335 if (p->penalty > value) { 336 value = p->value; 337 penalty[op][operand]--; 338 if (--(p->penalty) <= 0) { 339 p = p->next; 340 (void)free((char *)*pp); 341 *pp = p; 342 } 343 return(value); 344 } 345 value -= p->penalty; 346 } 347 /* 348 * We can only get here if the value from the penalty[] array doesn't 349 * correspond to the actual sum of penalties in the list. Provide an 350 * obscure message. 351 */ 352 (void)fprintf(stderr, "arithmetic: bug: inconsistent penalties\n"); 353 exit(1); 354 /* NOTREACHED */ 355 } 356 357 /* Return an index for the character op, which is one of [+-x/]. */ 358 opnum(op) 359 int op; 360 { 361 char *p; 362 363 if (op == 0 || (p = index(keylist, op)) == NULL) { 364 (void)fprintf(stderr, 365 "arithmetic: bug: op %c not in keylist %s\n", op, keylist); 366 exit(1); 367 } 368 return(p - keylist); 369 } 370 371 /* Print usage message and quit. */ 372 usage() 373 { 374 (void)fprintf(stderr, "usage: arithmetic [-o +-x/] [-r range]\n"); 375 exit(1); 376 } 377