1/* $NetBSD: arithmetic.c,v 1.26 2011/08/31 16:24:55 plunky 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#include <sys/cdefs.h> 36#ifndef lint 37__COPYRIGHT("@(#) Copyright (c) 1989, 1993\ 38 The Regents of the University of California. All rights reserved."); 39#endif /* not lint */ 40 41#ifndef lint 42#if 0 43static char sccsid[] = "@(#)arithmetic.c 8.1 (Berkeley) 5/31/93"; 44#else 45__RCSID("$NetBSD: arithmetic.c,v 1.26 2011/08/31 16:24:55 plunky 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 87static int getrandom(int, int, int); 88static void intr(int) __dead; 89static int opnum(int); 90static void penalise(int, int, int); 91static int problem(void); 92static void showstats(int); 93static void usage(void) __dead; 94 95static const char keylist[] = "+-x/"; 96static const char defaultkeys[] = "+-"; 97static const char *keys = defaultkeys; 98static int nkeys = sizeof(defaultkeys) - 1; 99static int rangemax = 10; 100static int nright, nwrong; 101static 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 */ 111int 112main(int argc, char **argv) 113{ 114 int ch, cnt; 115 116 /* Revoke setgid privileges */ 117 setgid(getgid()); 118 119 while ((ch = getopt(argc, argv, "r:o:")) != -1) 120 switch(ch) { 121 case 'o': { 122 const char *p; 123 124 for (p = keys = optarg; *p; ++p) 125 if (!strchr(keylist, *p)) 126 errx(1, "arithmetic: unknown key."); 127 nkeys = p - optarg; 128 break; 129 } 130 case 'r': 131 if ((rangemax = atoi(optarg)) <= 0) 132 errx(1, "arithmetic: invalid range."); 133 break; 134 case '?': 135 default: 136 usage(); 137 } 138 if (argc -= optind) 139 usage(); 140 141 /* Seed the random-number generator. */ 142 srandom((int)time(NULL)); 143 144 (void)signal(SIGINT, intr); 145 146 /* Now ask the questions. */ 147 for (;;) { 148 for (cnt = NQUESTS; cnt--;) 149 if (problem() == EOF) 150 exit(0); 151 showstats(0); 152 } 153 /* NOTREACHED */ 154} 155 156/* Handle interrupt character. Print score and exit. */ 157static void 158intr(int dummy __unused) 159{ 160 showstats(1); 161 exit(0); 162} 163 164/* Print score. Original `arithmetic' had a delay after printing it. */ 165static void 166showstats(int bool_sigint) 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 if(!bool_sigint) { 176 (void)printf("Press RETURN to continue...\n"); 177 while(!getchar()) ; 178 } 179 (void)printf("\n"); 180} 181 182/* 183 * Pick a problem and ask it. Keeps asking the same problem until supplied 184 * with the correct answer, or until EOF or interrupt is typed. Problems are 185 * selected such that the right operand and either the left operand (for +, x) 186 * or the correct result (for -, /) are in the range 0 to rangemax. Each wrong 187 * answer causes the numbers in the problem to be penalised, so that they are 188 * more likely to appear in subsequent problems. 189 */ 190static int 191problem(void) 192{ 193 char *p; 194 time_t start, finish; 195 int left, op, right, result; 196 char line[80]; 197 198 right = left = result = 0; 199 op = keys[random() % nkeys]; 200 if (op != '/') 201 right = getrandom(rangemax + 1, op, 1); 202retry: 203 /* Get the operands. */ 204 switch (op) { 205 case '+': 206 left = getrandom(rangemax + 1, op, 0); 207 result = left + right; 208 break; 209 case '-': 210 result = getrandom(rangemax + 1, op, 0); 211 left = right + result; 212 break; 213 case 'x': 214 left = getrandom(rangemax + 1, op, 0); 215 result = left * right; 216 break; 217 case '/': 218 right = getrandom(rangemax, op, 1) + 1; 219 result = getrandom(rangemax + 1, op, 0); 220 left = right * result + random() % right; 221 break; 222 } 223 224 /* 225 * A very big maxrange could cause negative values to pop 226 * up, owing to overflow. 227 */ 228 if (result < 0 || left < 0) 229 goto retry; 230 231 (void)printf("%d %c %d = ", left, op, right); 232 (void)fflush(stdout); 233 (void)time(&start); 234 235 /* 236 * Keep looping until the correct answer is given, or until EOF or 237 * interrupt is typed. 238 */ 239 for (;;) { 240 if (!fgets(line, sizeof(line), stdin)) { 241 (void)printf("\n"); 242 return(EOF); 243 } 244 for (p = line; *p && isspace((unsigned char)*p); ++p); 245 if (!isdigit((unsigned char)*p)) { 246 (void)printf("Please type a number.\n"); 247 continue; 248 } 249 if (atoi(p) == result) { 250 (void)printf("Right!\n"); 251 ++nright; 252 break; 253 } 254 /* Wrong answer; penalise and ask again. */ 255 (void)printf("What?\n"); 256 ++nwrong; 257 penalise(right, op, 1); 258 if (op == 'x' || op == '+') 259 penalise(left, op, 0); 260 else 261 penalise(result, op, 0); 262 } 263 264 /* 265 * Accumulate the time taken. Obviously rounding errors happen here; 266 * however they should cancel out, because some of the time you are 267 * charged for a partially elapsed second at the start, and some of 268 * the time you are not charged for a partially elapsed second at the 269 * end. 270 */ 271 (void)time(&finish); 272 qtime += finish - start; 273 return(0); 274} 275 276/* 277 * Here is the code for accumulating penalties against the numbers for which 278 * a wrong answer was given. The right operand and either the left operand 279 * (for +, x) or the result (for -, /) are stored in a list for the particular 280 * operation, and each becomes more likely to appear again in that operation. 281 * Initially, each number is charged a penalty of WRONGPENALTY, giving it that 282 * many extra chances of appearing. Each time it is selected because of this, 283 * its penalty is decreased by one; it is removed when it reaches 0. 284 * 285 * The penalty[] array gives the sum of all penalties in the list for 286 * each operation and each operand. The penlist[] array has the lists of 287 * penalties themselves. 288 */ 289 290static int penalty[sizeof(keylist) - 1][2]; 291static struct penalty { 292 int value, penalty; /* Penalised value and its penalty. */ 293 struct penalty *next; 294} *penlist[sizeof(keylist) - 1][2]; 295 296#define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */ 297 298/* 299 * Add a penalty for the number `value' to the list for operation `op', 300 * operand number `operand' (0 or 1). If we run out of memory, we just 301 * forget about the penalty (how likely is this, anyway?). 302 */ 303static void 304penalise(int value, int op, int operand) 305{ 306 struct penalty *p; 307 308 op = opnum(op); 309 if ((p = malloc(sizeof(*p))) == NULL) 310 return; 311 p->next = penlist[op][operand]; 312 penlist[op][operand] = p; 313 penalty[op][operand] += p->penalty = WRONGPENALTY; 314 p->value = value; 315} 316 317/* 318 * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1) 319 * of operation `op'. The random number we generate is either used directly 320 * as a value, or represents a position in the penalty list. If the latter, 321 * we find the corresponding value and return that, decreasing its penalty. 322 */ 323static int 324getrandom(int maxval, int op, int operand) 325{ 326 int value; 327 struct penalty **pp, *p; 328 329 op = opnum(op); 330 value = random() % (maxval + penalty[op][operand]); 331 332 /* 333 * 0 to maxval - 1 is a number to be used directly; bigger values 334 * are positions to be located in the penalty list. 335 */ 336 if (value < maxval) 337 return(value); 338 value -= maxval; 339 340 /* 341 * Find the penalty at position `value'; decrement its penalty and 342 * delete it if it reaches 0; return the corresponding value. 343 */ 344 for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) { 345 if (p->penalty > value) { 346 value = p->value; 347 penalty[op][operand]--; 348 if (--(p->penalty) <= 0) { 349 p = p->next; 350 (void)free((char *)*pp); 351 *pp = p; 352 } 353 return(value); 354 } 355 value -= p->penalty; 356 } 357 /* 358 * We can only get here if the value from the penalty[] array doesn't 359 * correspond to the actual sum of penalties in the list. Provide an 360 * obscure message. 361 */ 362 errx(1, "arithmetic: bug: inconsistent penalties."); 363 /* NOTREACHED */ 364} 365 366/* Return an index for the character op, which is one of [+-x/]. */ 367static int 368opnum(int op) 369{ 370 char *p; 371 372 if (op == 0 || (p = strchr(keylist, op)) == NULL) 373 errx(1, "arithmetic: bug: op %c not in keylist %s", 374 op, keylist); 375 return(p - keylist); 376} 377 378/* Print usage message and quit. */ 379static void 380usage(void) 381{ 382 (void)fprintf(stderr, "Usage: %s [-o +-x/] [-r range]\n", 383 getprogname()); 384 exit(1); 385} 386