1: /*      $NetBSD: arithmetic.c,v 1.21 2004/11/05 21:30:31 dsl 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\n\
   38:         The Regents of the University of California.  All rights reserved.\n");
   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 1.21 2004/11/05 21:30:31 dsl 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: int     getrandom(int, int, int);
   88: void    intr(int) __attribute__((__noreturn__));
   89: int     main(int, char *[]);
   90: int     opnum(int);
   91: void    penalise(int, int, int);
   92: int     problem(void);
   93: void    showstats(int);
   94: void    usage(void) __attribute__((__noreturn__));
   95: 
   96: const char keylist[] = "+-x/";
   97: const char defaultkeys[] = "+-";
   98: const char *keys = defaultkeys;
   99: int nkeys = sizeof(defaultkeys) - 1;
  100: int rangemax = 10;
  101: int nright, nwrong;
  102: time_t qtime;
  103: #define NQUESTS 20
  104: 
  105: /*
  106:  * Select keys from +-x/ to be asked addition, subtraction, multiplication,
  107:  * and division problems.  More than one key may be given.  The default is
  108:  * +-.  Specify a range to confine the operands to 0 - range.  Default upper
  109:  * bound is 10.  After every NQUESTS questions, statistics on the performance
  110:  * so far are printed.
  111:  */
  112: int
  113: main(argc, argv)
  114:         int argc;
  115:         char **argv;
  116: {
  117:         int ch, cnt;
  118: 
  119:         /* Revoke setgid privileges */
  120:         setregid(getgid(), getgid());
  121: 
  122:         while ((ch = getopt(argc, argv, "r:o:")) != -1)
  123:                 switch(ch) {
  124:                 case 'o': {
  125:                         const char *p;
  126: 
  127:                         for (p = keys = optarg; *p; ++p)
  128:                                 if (!strchr(keylist, *p))
  129:                                         errx(1, "arithmetic: unknown key.");
  130:                         nkeys = p - optarg;
  131:                         break;
  132:                 }
  133:                 case 'r':
  134:                         if ((rangemax = atoi(optarg)) <= 0)
  135:                                 errx(1, "arithmetic: invalid range.");
  136:                         break;
  137:                 case '?':
  138:                 default:
  139:                         usage();
  140:                 }
  141:         if (argc -= optind)
  142:                 usage();
  143: 
  144:         /* Seed the random-number generator. */
  145:         srandom((int)time((time_t *)NULL));
  146: 
  147:         (void)signal(SIGINT, intr);
  148: 
  149:         /* Now ask the questions. */
  150:         for (;;) {
  151:                 for (cnt = NQUESTS; cnt--;)
  152:                         if (problem() == EOF)
  153:                                 exit(0);
  154:                 showstats(0);
  155:         }
  156:         /* NOTREACHED */
  157: }
  158: 
  159: /* Handle interrupt character.  Print score and exit. */
  160: void
  161: intr(dummy)
  162:         int dummy __attribute__((__unused__));
  163: {
  164:         showstats(1);
  165:         exit(0);
  166: }
  167: 
  168: /* Print score.  Original `arithmetic' had a delay after printing it. */
  169: void
  170: showstats(bool_sigint)
  171:         int bool_sigint;
  172: {
  173:         if (nright + nwrong > 0) {
  174:                 (void)printf("\n\nRights %d; Wrongs %d; Score %d%%",
  175:                     nright, nwrong, (int)(100L * nright / (nright + nwrong)));
  176:                 if (nright > 0)
  177:         (void)printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n",
  178:                             (long)qtime, (float)qtime / nright);
  179:         }
  180:         if(!bool_sigint) {
  181:                 (void)printf("Press RETURN to continue...\n");
  182:                 while(!getchar()) ;
  183:         }
  184:         (void)printf("\n");
  185: }
  186: 
  187: /*
  188:  * Pick a problem and ask it.  Keeps asking the same problem until supplied
  189:  * with the correct answer, or until EOF or interrupt is typed.  Problems are
  190:  * selected such that the right operand and either the left operand (for +, x)
  191:  * or the correct result (for -, /) are in the range 0 to rangemax.  Each wrong
  192:  * answer causes the numbers in the problem to be penalised, so that they are
  193:  * more likely to appear in subsequent problems.
  194:  */
  195: int
  196: problem()
  197: {
  198:         char *p;
  199:         time_t start, finish;
  200:         int left, op, right, result;
  201:         char line[80];
  202: 
  203:         right = left = result = 0;
  204:         op = keys[random() % nkeys];
  205:         if (op != '/')
  206:                 right = getrandom(rangemax + 1, op, 1);
  207: retry:
  208:         /* Get the operands. */
  209:         switch (op) {
  210:         case '+':
  211:                 left = getrandom(rangemax + 1, op, 0);
  212:                 result = left + right;
  213:                 break;
  214:         case '-':
  215:                 result = getrandom(rangemax + 1, op, 0);
  216:                 left = right + result;
  217:                 break;
  218:         case 'x':
  219:                 left = getrandom(rangemax + 1, op, 0);
  220:                 result = left * right;
  221:                 break;
  222:         case '/':
  223:                 right = getrandom(rangemax, op, 1) + 1;
  224:                 result = getrandom(rangemax + 1, op, 0);
  225:                 left = right * result + random() % right;
  226:                 break;
  227:         }
  228: 
  229:         /*
  230:          * A very big maxrange could cause negative values to pop
  231:          * up, owing to overflow.
  232:          */
  233:         if (result < 0 || left < 0)
  234:                 goto retry;
  235: 
  236:         (void)printf("%d %c %d =   ", left, op, right);
  237:         (void)fflush(stdout);
  238:         (void)time(&start);
  239: 
  240:         /*
  241:          * Keep looping until the correct answer is given, or until EOF or
  242:          * interrupt is typed.
  243:          */
  244:         for (;;) {
  245:                 if (!fgets(line, sizeof(line), stdin)) {
  246:                         (void)printf("\n");
  247:                         return(EOF);
  248:                 }
  249:                 for (p = line; *p && isspace((unsigned char)*p); ++p);
  250:                 if (!isdigit((unsigned char)*p)) {
  251:                         (void)printf("Please type a number.\n");
  252:                         continue;
  253:                 }
  254:                 if (atoi(p) == result) {
  255:                         (void)printf("Right!\n");
  256:                         ++nright;
  257:                         break;
  258:                 }
  259:                 /* Wrong answer; penalise and ask again. */
  260:                 (void)printf("What?\n");
  261:                 ++nwrong;
  262:                 penalise(right, op, 1);
  263:                 if (op == 'x' || op == '+')
  264:                         penalise(left, op, 0);
  265:                 else
  266:                         penalise(result, op, 0);
  267:         }
  268: 
  269:         /*
  270:          * Accumulate the time taken.  Obviously rounding errors happen here;
  271:          * however they should cancel out, because some of the time you are
  272:          * charged for a partially elapsed second at the start, and some of
  273:          * the time you are not charged for a partially elapsed second at the
  274:          * end.
  275:          */
  276:         (void)time(&finish);
  277:         qtime += finish - start;
  278:         return(0);
  279: }
  280: 
  281: /*
  282:  * Here is the code for accumulating penalties against the numbers for which
  283:  * a wrong answer was given.  The right operand and either the left operand
  284:  * (for +, x) or the result (for -, /) are stored in a list for the particular
  285:  * operation, and each becomes more likely to appear again in that operation.
  286:  * Initially, each number is charged a penalty of WRONGPENALTY, giving it that
  287:  * many extra chances of appearing.  Each time it is selected because of this,
  288:  * its penalty is decreased by one; it is removed when it reaches 0.
  289:  *
  290:  * The penalty[] array gives the sum of all penalties in the list for
  291:  * each operation and each operand.  The penlist[] array has the lists of
  292:  * penalties themselves.
  293:  */
  294: 
  295: int penalty[sizeof(keylist) - 1][2];
  296: struct penalty {
  297:         int value, penalty;    /* Penalised value and its penalty. */
  298:         struct penalty *next;
  299: } *penlist[sizeof(keylist) - 1][2];
  300: 
  301: #define WRONGPENALTY    5  /* Perhaps this should depend on maxrange. */
  302: 
  303: /*
  304:  * Add a penalty for the number `value' to the list for operation `op',
  305:  * operand number `operand' (0 or 1).  If we run out of memory, we just
  306:  * forget about the penalty (how likely is this, anyway?).
  307:  */
  308: void
  309: penalise(value, op, operand)
  310:         int value, op, operand;
  311: {
  312:         struct penalty *p;
  313: 
  314:         op = opnum(op);
  315:         if ((p = (struct penalty *)malloc((u_int)sizeof(*p))) == NULL)
  316:                 return;
  317:         p->next = penlist[op][operand];
  318:         penlist[op][operand] = p;
  319:         penalty[op][operand] += p->penalty = WRONGPENALTY;
  320:         p->value = value;
  321: }
  322: 
  323: /*
  324:  * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1)
  325:  * of operation `op'.  The random number we generate is either used directly
  326:  * as a value, or represents a position in the penalty list.  If the latter,
  327:  * we find the corresponding value and return that, decreasing its penalty.
  328:  */
  329: int
  330: getrandom(maxval, op, operand)
  331:         int maxval, op, operand;
  332: {
  333:         int value;
  334:         struct penalty **pp, *p;
  335: 
  336:         op = opnum(op);
  337:         value = random() % (maxval + penalty[op][operand]);
  338: 
  339:         /*
  340:          * 0 to maxval - 1 is a number to be used directly; bigger values
  341:          * are positions to be located in the penalty list.
  342:          */
  343:         if (value < maxval)
  344:                 return(value);
  345:         value -= maxval;
  346: 
  347:         /*
  348:          * Find the penalty at position `value'; decrement its penalty and
  349:          * delete it if it reaches 0; return the corresponding value.
  350:          */
  351:         for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) {
  352:                 if (p->penalty > value) {
  353:                         value = p->value;
  354:                         penalty[op][operand]--;
  355:                         if (--(p->penalty) <= 0) {
  356:                                 p = p->next;
  357:                                 (void)free((char *)*pp);
  358:                                 *pp = p;
  359:                         }
  360:                         return(value);
  361:                 }
  362:                 value -= p->penalty;
  363:         }
  364:         /*
  365:          * We can only get here if the value from the penalty[] array doesn't
  366:          * correspond to the actual sum of penalties in the list.  Provide an
  367:          * obscure message.
  368:          */
  369:         errx(1, "arithmetic: bug: inconsistent penalties.");
  370:         /* NOTREACHED */
  371: }
  372: 
  373: /* Return an index for the character op, which is one of [+-x/]. */
  374: int
  375: opnum(op)
  376:         int op;
  377: {
  378:         char *p;
  379: 
  380:         if (op == 0 || (p = strchr(keylist, op)) == NULL)
  381:                 errx(1, "arithmetic: bug: op %c not in keylist %s",
  382:                     op, keylist);
  383:         return(p - keylist);
  384: }
  385: 
  386: /* Print usage message and quit. */
  387: void
  388: usage()
  389: {
  390:         (void)fprintf(stderr, "Usage: %s [-o +-x/] [-r range]\n",
  391:                 getprogname());
  392:         exit(1);
  393: }