games/arithmetic/arithmetic.c

   1 /*      $NetBSD: arithmetic.c,v 1.27 2012/06/19 05:46:08 dholland 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
  43 static char sccsid[] = "@(#)arithmetic.c        8.1 (Berkeley) 5/31/93";
  44 #else
  45 __RCSID("$NetBSD: arithmetic.c,v 1.27 2012/06/19 05:46:08 dholland 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 static int      getrandom(int, int, int);
  88 static void     intr(int) __dead;
  89 static int      opnum(int);
  90 static void     penalise(int, int, int);
  91 static int      problem(void);
  92 static void     showstats(int);
  93 static void     usage(void) __dead;
  94
  95 static const char keylist[] = "+-x/";
  96 static const char defaultkeys[] = "+-";
  97 static const char *keys = defaultkeys;
  98 static int nkeys = sizeof(defaultkeys) - 1;
  99 static int rangemax = 10;
 100 static int nright, nwrong;
 101 static 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         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. */
 157 static void
 158 intr(int dummy __unused)
 159 {
 160         showstats(1);
 161         exit(0);
 162 }
 163
 164 /* Print score.  Original `arithmetic' had a delay after printing it. */
 165 static void
 166 showstats(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  */
 190 static int
 191 problem(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);
 202 retry:
 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
 290 static int penalty[sizeof(keylist) - 1][2];
 291 static 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  */
 303 static void
 304 penalise(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  */
 323 static int
 324 getrandom(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/]. */
 367 static int
 368 opnum(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. */
 379 static void
 380 usage(void)
 381 {
 382         (void)fprintf(stderr, "Usage: %s [-o +-x/] [-r range]\n",
 383                 getprogname());
 384         exit(1);
 385 }