375 lines
11 KiB
C
375 lines
11 KiB
C
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/*
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* Copyright (c) 1989, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Eamonn McManus of Trinity College Dublin.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef lint
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static char copyright[] =
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"@(#) Copyright (c) 1989, 1993\n\
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The Regents of the University of California. All rights reserved.\n";
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#endif /* not lint */
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#ifndef lint
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static char sccsid[] = "@(#)arithmetic.c 8.1 (Berkeley) 5/31/93";
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#endif /* not lint */
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/*
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* By Eamonn McManus, Trinity College Dublin <emcmanus@cs.tcd.ie>.
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*
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* The operation of this program mimics that of the standard Unix game
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* `arithmetic'. I've made it as close as I could manage without examining
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* the source code. The principal differences are:
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*
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* The method of biasing towards numbers that had wrong answers in the past
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* is different; original `arithmetic' seems to retain the bias forever,
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* whereas this program lets the bias gradually decay as it is used.
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*
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* Original `arithmetic' delays for some period (3 seconds?) after printing
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* the score. I saw no reason for this delay, so I scrapped it.
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*
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* There is no longer a limitation on the maximum range that can be supplied
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* to the program. The original program required it to be less than 100.
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* Anomalous results may occur with this program if ranges big enough to
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* allow overflow are given.
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*
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* I have obviously not attempted to duplicate bugs in the original. It
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* would go into an infinite loop if invoked as `arithmetic / 0'. It also
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* did not recognise an EOF in its input, and would continue trying to read
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* after it. It did not check that the input was a valid number, treating any
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* garbage as 0. Finally, it did not flush stdout after printing its prompt,
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* so in the unlikely event that stdout was not a terminal, it would not work
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* properly.
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*/
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#include <sys/types.h>
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#include <sys/signal.h>
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#include <ctype.h>
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#include <stdio.h>
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#include <string.h>
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char keylist[] = "+-x/";
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char defaultkeys[] = "+-";
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char *keys = defaultkeys;
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int nkeys = sizeof(defaultkeys) - 1;
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int rangemax = 10;
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int nright, nwrong;
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time_t qtime;
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#define NQUESTS 20
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/*
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* Select keys from +-x/ to be asked addition, subtraction, multiplication,
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* and division problems. More than one key may be given. The default is
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* +-. Specify a range to confine the operands to 0 - range. Default upper
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* bound is 10. After every NQUESTS questions, statistics on the performance
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* so far are printed.
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*/
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void
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main(argc, argv)
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int argc;
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char **argv;
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{
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extern char *optarg;
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extern int optind;
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int ch, cnt;
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void intr();
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while ((ch = getopt(argc, argv, "r:o:")) != EOF)
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switch(ch) {
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case 'o': {
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register char *p;
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for (p = keys = optarg; *p; ++p)
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if (!index(keylist, *p)) {
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(void)fprintf(stderr,
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"arithmetic: unknown key.\n");
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exit(1);
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}
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nkeys = p - optarg;
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break;
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}
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case 'r':
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if ((rangemax = atoi(optarg)) <= 0) {
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(void)fprintf(stderr,
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"arithmetic: invalid range.\n");
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exit(1);
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}
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break;
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case '?':
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default:
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usage();
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}
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if (argc -= optind)
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usage();
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/* Seed the random-number generator. */
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srandom((int)time((time_t *)NULL));
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(void)signal(SIGINT, intr);
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/* Now ask the questions. */
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for (;;) {
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for (cnt = NQUESTS; cnt--;)
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if (problem() == EOF)
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exit(0);
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showstats();
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}
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/* NOTREACHED */
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}
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/* Handle interrupt character. Print score and exit. */
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void
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intr()
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{
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showstats();
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exit(0);
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}
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/* Print score. Original `arithmetic' had a delay after printing it. */
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showstats()
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{
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if (nright + nwrong > 0) {
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(void)printf("\n\nRights %d; Wrongs %d; Score %d%%",
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nright, nwrong, (int)(100L * nright / (nright + nwrong)));
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if (nright > 0)
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(void)printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n",
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(long)qtime, (float)qtime / nright);
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}
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(void)printf("\n");
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}
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/*
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* Pick a problem and ask it. Keeps asking the same problem until supplied
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* with the correct answer, or until EOF or interrupt is typed. Problems are
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* selected such that the right operand and either the left operand (for +, x)
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* or the correct result (for -, /) are in the range 0 to rangemax. Each wrong
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* answer causes the numbers in the problem to be penalised, so that they are
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* more likely to appear in subsequent problems.
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*/
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problem()
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{
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register char *p;
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time_t start, finish;
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int left, op, right, result;
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char line[80];
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op = keys[random() % nkeys];
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if (op != '/')
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right = getrandom(rangemax + 1, op, 1);
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retry:
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/* Get the operands. */
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switch (op) {
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case '+':
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left = getrandom(rangemax + 1, op, 0);
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result = left + right;
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break;
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case '-':
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result = getrandom(rangemax + 1, op, 0);
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left = right + result;
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break;
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case 'x':
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left = getrandom(rangemax + 1, op, 0);
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result = left * right;
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break;
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case '/':
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right = getrandom(rangemax, op, 1) + 1;
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result = getrandom(rangemax + 1, op, 0);
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left = right * result + random() % right;
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break;
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}
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/*
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* A very big maxrange could cause negative values to pop
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* up, owing to overflow.
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*/
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if (result < 0 || left < 0)
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goto retry;
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(void)printf("%d %c %d = ", left, op, right);
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(void)fflush(stdout);
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(void)time(&start);
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/*
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* Keep looping until the correct answer is given, or until EOF or
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* interrupt is typed.
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*/
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for (;;) {
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if (!fgets(line, sizeof(line), stdin)) {
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(void)printf("\n");
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return(EOF);
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}
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for (p = line; *p && isspace(*p); ++p);
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if (!isdigit(*p)) {
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(void)printf("Please type a number.\n");
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continue;
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}
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if (atoi(p) == result) {
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(void)printf("Right!\n");
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++nright;
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break;
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}
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/* Wrong answer; penalise and ask again. */
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(void)printf("What?\n");
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++nwrong;
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penalise(right, op, 1);
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if (op == 'x' || op == '+')
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penalise(left, op, 0);
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else
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penalise(result, op, 0);
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}
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/*
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* Accumulate the time taken. Obviously rounding errors happen here;
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* however they should cancel out, because some of the time you are
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* charged for a partially elapsed second at the start, and some of
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* the time you are not charged for a partially elapsed second at the
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* end.
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*/
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(void)time(&finish);
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qtime += finish - start;
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return(0);
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}
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/*
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* Here is the code for accumulating penalties against the numbers for which
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* a wrong answer was given. The right operand and either the left operand
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* (for +, x) or the result (for -, /) are stored in a list for the particular
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* operation, and each becomes more likely to appear again in that operation.
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* Initially, each number is charged a penalty of WRONGPENALTY, giving it that
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* many extra chances of appearing. Each time it is selected because of this,
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* its penalty is decreased by one; it is removed when it reaches 0.
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*
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* The penalty[] array gives the sum of all penalties in the list for
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* each operation and each operand. The penlist[] array has the lists of
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* penalties themselves.
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*/
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int penalty[sizeof(keylist) - 1][2];
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struct penalty {
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int value, penalty; /* Penalised value and its penalty. */
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struct penalty *next;
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} *penlist[sizeof(keylist) - 1][2];
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#define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */
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/*
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* Add a penalty for the number `value' to the list for operation `op',
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* operand number `operand' (0 or 1). If we run out of memory, we just
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* forget about the penalty (how likely is this, anyway?).
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*/
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penalise(value, op, operand)
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int value, op, operand;
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{
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struct penalty *p;
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char *malloc();
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op = opnum(op);
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if ((p = (struct penalty *)malloc((u_int)sizeof(*p))) == NULL)
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return;
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p->next = penlist[op][operand];
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penlist[op][operand] = p;
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penalty[op][operand] += p->penalty = WRONGPENALTY;
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p->value = value;
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}
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/*
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* Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1)
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* of operation `op'. The random number we generate is either used directly
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* as a value, or represents a position in the penalty list. If the latter,
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* we find the corresponding value and return that, decreasing its penalty.
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*/
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getrandom(maxval, op, operand)
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int maxval, op, operand;
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{
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int value;
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register struct penalty **pp, *p;
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op = opnum(op);
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value = random() % (maxval + penalty[op][operand]);
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/*
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* 0 to maxval - 1 is a number to be used directly; bigger values
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* are positions to be located in the penalty list.
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*/
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if (value < maxval)
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return(value);
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value -= maxval;
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/*
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* Find the penalty at position `value'; decrement its penalty and
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* delete it if it reaches 0; return the corresponding value.
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*/
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for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) {
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if (p->penalty > value) {
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value = p->value;
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penalty[op][operand]--;
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if (--(p->penalty) <= 0) {
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p = p->next;
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(void)free((char *)*pp);
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*pp = p;
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}
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return(value);
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}
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value -= p->penalty;
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}
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/*
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* We can only get here if the value from the penalty[] array doesn't
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* correspond to the actual sum of penalties in the list. Provide an
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* obscure message.
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*/
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(void)fprintf(stderr, "arithmetic: bug: inconsistent penalties\n");
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exit(1);
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/* NOTREACHED */
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}
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/* Return an index for the character op, which is one of [+-x/]. */
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opnum(op)
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int op;
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{
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char *p;
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if (op == 0 || (p = index(keylist, op)) == NULL) {
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(void)fprintf(stderr,
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"arithmetic: bug: op %c not in keylist %s\n", op, keylist);
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exit(1);
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}
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return(p - keylist);
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}
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/* Print usage message and quit. */
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usage()
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{
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(void)fprintf(stderr, "usage: arithmetic [-o +-x/] [-r range]\n");
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exit(1);
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}
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