1 /*- 2 * Copyright (c) 1989, 1993 3 * The Regents of the University of California. 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. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#) Copyright (c) 1989, 1993 The Regents of the University of California. All rights reserved. 33 * @(#)arithmetic.c 8.1 (Berkeley) 5/31/93 34 * $FreeBSD: src/games/arithmetic/arithmetic.c,v 1.10 1999/12/12 06:40:28 billf Exp $ 35 */ 36 37 /* 38 * By Eamonn McManus, Trinity College Dublin <emcmanus@cs.tcd.ie>. 39 * 40 * The operation of this program mimics that of the standard Unix game 41 * `arithmetic'. I've made it as close as I could manage without examining 42 * the source code. The principal differences are: 43 * 44 * The method of biasing towards numbers that had wrong answers in the past 45 * is different; original `arithmetic' seems to retain the bias forever, 46 * whereas this program lets the bias gradually decay as it is used. 47 * 48 * Original `arithmetic' delays for some period (3 seconds?) after printing 49 * the score. I saw no reason for this delay, so I scrapped it. 50 * 51 * There is no longer a limitation on the maximum range that can be supplied 52 * to the program. The original program required it to be less than 100. 53 * Anomalous results may occur with this program if ranges big enough to 54 * allow overflow are given. 55 * 56 * I have obviously not attempted to duplicate bugs in the original. It 57 * would go into an infinite loop if invoked as `arithmetic / 0'. It also 58 * did not recognise an EOF in its input, and would continue trying to read 59 * after it. It did not check that the input was a valid number, treating any 60 * garbage as 0. Finally, it did not flush stdout after printing its prompt, 61 * so in the unlikely event that stdout was not a terminal, it would not work 62 * properly. 63 */ 64 65 #include <sys/types.h> 66 #include <ctype.h> 67 #include <signal.h> 68 #include <stdio.h> 69 #include <stdlib.h> 70 #include <string.h> 71 #include <time.h> 72 #include <unistd.h> 73 74 int getrandom(int, int, int); 75 void intr(int); 76 int opnum(int); 77 void penalise(int, int, int); 78 int problem(void); 79 void showstats(void); 80 static void usage(void); 81 82 const char keylist[] = "+-x/"; 83 const char defaultkeys[] = "+-"; 84 const char *keys = defaultkeys; 85 int nkeys = sizeof(defaultkeys) - 1; 86 int rangemax = 10; 87 int nright, nwrong; 88 time_t qtime; 89 #define NQUESTS 20 90 91 /* 92 * Select keys from +-x/ to be asked addition, subtraction, multiplication, 93 * and division problems. More than one key may be given. The default is 94 * +-. Specify a range to confine the operands to 0 - range. Default upper 95 * bound is 10. After every NQUESTS questions, statistics on the performance 96 * so far are printed. 97 */ 98 int 99 main(int argc, char *argv[]) 100 { 101 int ch, cnt; 102 103 /* Revoke setgid privileges */ 104 setgid(getgid()); 105 106 while ((ch = getopt(argc, argv, "r:o:")) != -1) 107 switch(ch) { 108 case 'o': { 109 const char *p; 110 111 for (p = keys = optarg; *p; ++p) 112 if (!index(keylist, *p)) { 113 fprintf(stderr, 114 "arithmetic: unknown key.\n"); 115 exit(1); 116 } 117 nkeys = p - optarg; 118 break; 119 } 120 case 'r': 121 if ((rangemax = atoi(optarg)) <= 0) { 122 fprintf(stderr, 123 "arithmetic: invalid range.\n"); 124 exit(1); 125 } 126 break; 127 case '?': 128 default: 129 usage(); 130 } 131 if (argc -= optind) 132 usage(); 133 134 /* Seed the random-number generator. */ 135 srandomdev(); 136 137 signal(SIGINT, intr); 138 139 /* Now ask the questions. */ 140 for (;;) { 141 for (cnt = NQUESTS; cnt--;) 142 if (problem() == EOF) 143 exit(0); 144 showstats(); 145 } 146 /* NOTREACHED */ 147 } 148 149 /* Handle interrupt character. Print score and exit. */ 150 void 151 intr(__unused int sig) 152 { 153 showstats(); 154 exit(0); 155 } 156 157 /* Print score. Original `arithmetic' had a delay after printing it. */ 158 void 159 showstats(void) 160 { 161 if (nright + nwrong > 0) { 162 printf("\n\nRights %d; Wrongs %d; Score %d%%", 163 nright, nwrong, (int)(100L * nright / (nright + nwrong))); 164 if (nright > 0) 165 printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n", 166 (long)qtime, (float)qtime / nright); 167 } 168 printf("\n"); 169 } 170 171 /* 172 * Pick a problem and ask it. Keeps asking the same problem until supplied 173 * with the correct answer, or until EOF or interrupt is typed. Problems are 174 * selected such that the right operand and either the left operand (for +, x) 175 * or the correct result (for -, /) are in the range 0 to rangemax. Each wrong 176 * answer causes the numbers in the problem to be penalised, so that they are 177 * more likely to appear in subsequent problems. 178 */ 179 int 180 problem(void) 181 { 182 char *p; 183 time_t start, finish; 184 int left, op, right, result; 185 char line[80]; 186 187 left = 0; 188 right = 0; 189 result = 0; 190 op = keys[random() % nkeys]; 191 if (op != '/') 192 right = getrandom(rangemax + 1, op, 1); 193 retry: 194 /* Get the operands. */ 195 switch (op) { 196 case '+': 197 left = getrandom(rangemax + 1, op, 0); 198 result = left + right; 199 break; 200 case '-': 201 result = getrandom(rangemax + 1, op, 0); 202 left = right + result; 203 break; 204 case 'x': 205 left = getrandom(rangemax + 1, op, 0); 206 result = left * right; 207 break; 208 case '/': 209 right = getrandom(rangemax, op, 1) + 1; 210 result = getrandom(rangemax + 1, op, 0); 211 left = right * result + random() % right; 212 break; 213 } 214 215 /* 216 * A very big maxrange could cause negative values to pop 217 * up, owing to overflow. 218 */ 219 if (result < 0 || left < 0) 220 goto retry; 221 222 printf("%d %c %d = ", left, op, right); 223 fflush(stdout); 224 time(&start); 225 226 /* 227 * Keep looping until the correct answer is given, or until EOF or 228 * interrupt is typed. 229 */ 230 for (;;) { 231 if (!fgets(line, sizeof(line), stdin)) { 232 printf("\n"); 233 return(EOF); 234 } 235 for (p = line; *p && isspace(*p); ++p); 236 if (!isdigit(*p)) { 237 printf("Please type a number.\n"); 238 continue; 239 } 240 if (atoi(p) == result) { 241 printf("Right!\n"); 242 ++nright; 243 break; 244 } 245 /* Wrong answer; penalise and ask again. */ 246 printf("What?\n"); 247 ++nwrong; 248 penalise(right, op, 1); 249 if (op == 'x' || op == '+') 250 penalise(left, op, 0); 251 else 252 penalise(result, op, 0); 253 } 254 255 /* 256 * Accumulate the time taken. Obviously rounding errors happen here; 257 * however they should cancel out, because some of the time you are 258 * charged for a partially elapsed second at the start, and some of 259 * the time you are not charged for a partially elapsed second at the 260 * end. 261 */ 262 time(&finish); 263 qtime += finish - start; 264 return(0); 265 } 266 267 /* 268 * Here is the code for accumulating penalties against the numbers for which 269 * a wrong answer was given. The right operand and either the left operand 270 * (for +, x) or the result (for -, /) are stored in a list for the particular 271 * operation, and each becomes more likely to appear again in that operation. 272 * Initially, each number is charged a penalty of WRONGPENALTY, giving it that 273 * many extra chances of appearing. Each time it is selected because of this, 274 * its penalty is decreased by one; it is removed when it reaches 0. 275 * 276 * The penalty[] array gives the sum of all penalties in the list for 277 * each operation and each operand. The penlist[] array has the lists of 278 * penalties themselves. 279 */ 280 281 int penalty[sizeof(keylist) - 1][2]; 282 struct penalty { 283 int value, penalty; /* Penalised value and its penalty. */ 284 struct penalty *next; 285 } *penlist[sizeof(keylist) - 1][2]; 286 287 #define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */ 288 289 /* 290 * Add a penalty for the number `value' to the list for operation `op', 291 * operand number `operand' (0 or 1). If we run out of memory, we just 292 * forget about the penalty (how likely is this, anyway?). 293 */ 294 void 295 penalise(int value, int op, int operand) 296 { 297 struct penalty *p; 298 299 op = opnum(op); 300 if ((p = malloc(sizeof(*p))) == NULL) 301 return; 302 p->next = penlist[op][operand]; 303 penlist[op][operand] = p; 304 penalty[op][operand] += p->penalty = WRONGPENALTY; 305 p->value = value; 306 } 307 308 /* 309 * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1) 310 * of operation `op'. The random number we generate is either used directly 311 * as a value, or represents a position in the penalty list. If the latter, 312 * we find the corresponding value and return that, decreasing its penalty. 313 */ 314 int 315 getrandom(int maxval, int op, int operand) 316 { 317 int value; 318 struct penalty **pp, *p; 319 320 op = opnum(op); 321 value = random() % (maxval + penalty[op][operand]); 322 323 /* 324 * 0 to maxval - 1 is a number to be used directly; bigger values 325 * are positions to be located in the penalty list. 326 */ 327 if (value < maxval) 328 return(value); 329 value -= maxval; 330 331 /* 332 * Find the penalty at position `value'; decrement its penalty and 333 * delete it if it reaches 0; return the corresponding value. 334 */ 335 for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) { 336 if (p->penalty > value) { 337 value = p->value; 338 penalty[op][operand]--; 339 if (--(p->penalty) <= 0) { 340 p = p->next; 341 free((char *)*pp); 342 *pp = p; 343 } 344 return(value); 345 } 346 value -= p->penalty; 347 } 348 /* 349 * We can only get here if the value from the penalty[] array doesn't 350 * correspond to the actual sum of penalties in the list. Provide an 351 * obscure message. 352 */ 353 fprintf(stderr, "arithmetic: bug: inconsistent penalties\n"); 354 exit(1); 355 /* NOTREACHED */ 356 } 357 358 /* Return an index for the character op, which is one of [+-x/]. */ 359 int 360 opnum(int op) 361 { 362 char *p; 363 364 if (op == 0 || (p = index(keylist, op)) == NULL) { 365 fprintf(stderr, 366 "arithmetic: bug: op %c not in keylist %s\n", op, keylist); 367 exit(1); 368 } 369 return(p - keylist); 370 } 371 372 /* Print usage message and quit. */ 373 static void 374 usage(void) 375 { 376 fprintf(stderr, "usage: arithmetic [-o +-x/] [-r range]\n"); 377 exit(1); 378 } 379