--- /dev/null
+.\" $NetBSD: arithmetic.6,v 1.12 2009/03/11 13:00:37 joerg Exp $
+.\"
+.\" Copyright (c) 1989, 1993
+.\" The Regents of the University of California. All rights reserved.
+.\"
+.\" This code is derived from software contributed to Berkeley by
+.\" Eamonn McManus of Trinity College Dublin.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\" notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\" notice, this list of conditions and the following disclaimer in the
+.\" documentation and/or other materials provided with the distribution.
+.\" 3. Neither the name of the University nor the names of its contributors
+.\" may be used to endorse or promote products derived from this software
+.\" without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" @(#)arithmetic.6 8.1 (Berkeley) 5/31/93
+.\"
+.Dd May 31, 1993
+.Dt ARITHMETIC 6
+.Os
+.Sh NAME
+.Nm arithmetic
+.Nd quiz on simple arithmetic
+.Sh SYNOPSIS
+.Nm
+.Op Fl o Ar +\-x/
+.Op Fl r Ar range
+.Sh DESCRIPTION
+.Nm
+asks you to solve problems in simple arithmetic.
+Each question must be answered correctly before going on to the next.
+After every 20 problems, it prints the score so far and the time taken.
+You can quit at any time by typing the interrupt or end-of-file character.
+.Pp
+The options are as follows:
+.Bl -tag -width indent
+.It Fl o
+By default,
+.Nm
+asks questions on addition of numbers from 0 to 10, and corresponding
+subtraction.
+By supplying one or more of the characters
+.Ar +\-x/ ,
+you can ask for problems in addition, subtraction, multiplication, and
+division, respectively.
+If you give one of these characters more than once, that kind of problem
+will be asked correspondingly more often.
+.It Fl r
+If a
+.Ar range
+is supplied,
+.Nm
+selects the numbers in its problems in the following way.
+For addition and multiplication, the numbers to be added or multiplied
+are between 0 and
+.Ar range ,
+inclusive.
+For subtraction and division, both the required result and the number to
+divide by or subtract will be between 0 and
+.Ar range .
+(Of course,
+.Nm
+will not ask you to divide by 0.)
+The default
+.Ar range
+is 10.
+.El
+.Pp
+When you get a problem wrong,
+.Nm
+will remember the numbers involved, and will tend to select those numbers
+more often than others, in problems of the same sort.
+Eventually it will forgive and forget.
+.Pp
+.Nm
+cannot be persuaded to tell you the right answer.
+You must work it out for yourself.
+.Sh DIAGNOSTICS
+.Dq What?
+if you get a question wrong.
+.Dq Right!
+if you get it right.
+.Dq Please type a number.
+if
+.Nm
+doesn't understand what you typed.
+.Sh SEE ALSO
+.Xr bc 1 ,
+.Xr dc 1
--- /dev/null
+/* $NetBSD: arithmetic.c,v 1.27 2012/06/19 05:46:08 dholland Exp $ */
+
+/*
+ * Copyright (c) 1989, 1993
+ * The Regents of the University of California. All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Eamonn McManus of Trinity College Dublin.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+#ifndef lint
+__COPYRIGHT("@(#) Copyright (c) 1989, 1993\
+ The Regents of the University of California. All rights reserved.");
+#endif /* not lint */
+
+#ifndef lint
+#if 0
+static char sccsid[] = "@(#)arithmetic.c 8.1 (Berkeley) 5/31/93";
+#else
+__RCSID("$NetBSD: arithmetic.c,v 1.27 2012/06/19 05:46:08 dholland Exp $");
+#endif
+#endif /* not lint */
+
+/*
+ * By Eamonn McManus, Trinity College Dublin <emcmanus@cs.tcd.ie>.
+ *
+ * The operation of this program mimics that of the standard Unix game
+ * `arithmetic'. I've made it as close as I could manage without examining
+ * the source code. The principal differences are:
+ *
+ * The method of biasing towards numbers that had wrong answers in the past
+ * is different; original `arithmetic' seems to retain the bias forever,
+ * whereas this program lets the bias gradually decay as it is used.
+ *
+ * Original `arithmetic' delays for some period (3 seconds?) after printing
+ * the score. I saw no reason for this delay, so I scrapped it.
+ *
+ * There is no longer a limitation on the maximum range that can be supplied
+ * to the program. The original program required it to be less than 100.
+ * Anomalous results may occur with this program if ranges big enough to
+ * allow overflow are given.
+ *
+ * I have obviously not attempted to duplicate bugs in the original. It
+ * would go into an infinite loop if invoked as `arithmetic / 0'. It also
+ * did not recognise an EOF in its input, and would continue trying to read
+ * after it. It did not check that the input was a valid number, treating any
+ * garbage as 0. Finally, it did not flush stdout after printing its prompt,
+ * so in the unlikely event that stdout was not a terminal, it would not work
+ * properly.
+ */
+
+#include <sys/types.h>
+#include <err.h>
+#include <ctype.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+static int getrandom(int, int, int);
+static void intr(int) __dead;
+static int opnum(int);
+static void penalise(int, int, int);
+static int problem(void);
+static void showstats(int);
+static void usage(void) __dead;
+
+static const char keylist[] = "+-x/";
+static const char defaultkeys[] = "+-";
+static const char *keys = defaultkeys;
+static int nkeys = sizeof(defaultkeys) - 1;
+static int rangemax = 10;
+static int nright, nwrong;
+static time_t qtime;
+#define NQUESTS 20
+
+/*
+ * Select keys from +-x/ to be asked addition, subtraction, multiplication,
+ * and division problems. More than one key may be given. The default is
+ * +-. Specify a range to confine the operands to 0 - range. Default upper
+ * bound is 10. After every NQUESTS questions, statistics on the performance
+ * so far are printed.
+ */
+int
+main(int argc, char **argv)
+{
+ int ch, cnt;
+
+ /* Revoke setgid privileges */
+ setgid(getgid());
+
+ while ((ch = getopt(argc, argv, "r:o:")) != -1)
+ switch(ch) {
+ case 'o': {
+ const char *p;
+
+ for (p = keys = optarg; *p; ++p)
+ if (!strchr(keylist, *p))
+ errx(1, "arithmetic: unknown key.");
+ nkeys = p - optarg;
+ break;
+ }
+ case 'r':
+ if ((rangemax = atoi(optarg)) <= 0)
+ errx(1, "arithmetic: invalid range.");
+ break;
+ case '?':
+ default:
+ usage();
+ }
+ if (argc -= optind)
+ usage();
+
+ /* Seed the random-number generator. */
+ srandom((int)time(NULL));
+
+ (void)signal(SIGINT, intr);
+
+ /* Now ask the questions. */
+ for (;;) {
+ for (cnt = NQUESTS; cnt--;)
+ if (problem() == EOF)
+ exit(0);
+ showstats(0);
+ }
+ /* NOTREACHED */
+}
+
+/* Handle interrupt character. Print score and exit. */
+static void
+intr(int dummy __unused)
+{
+ showstats(1);
+ exit(0);
+}
+
+/* Print score. Original `arithmetic' had a delay after printing it. */
+static void
+showstats(int bool_sigint)
+{
+ if (nright + nwrong > 0) {
+ (void)printf("\n\nRights %d; Wrongs %d; Score %d%%",
+ nright, nwrong, (int)(100L * nright / (nright + nwrong)));
+ if (nright > 0)
+ (void)printf("\nTotal time %ld seconds; %.1f seconds per problem\n\n",
+ (long)qtime, (float)qtime / nright);
+ }
+ if(!bool_sigint) {
+ (void)printf("Press RETURN to continue...\n");
+ while(!getchar()) ;
+ }
+ (void)printf("\n");
+}
+
+/*
+ * Pick a problem and ask it. Keeps asking the same problem until supplied
+ * with the correct answer, or until EOF or interrupt is typed. Problems are
+ * selected such that the right operand and either the left operand (for +, x)
+ * or the correct result (for -, /) are in the range 0 to rangemax. Each wrong
+ * answer causes the numbers in the problem to be penalised, so that they are
+ * more likely to appear in subsequent problems.
+ */
+static int
+problem(void)
+{
+ char *p;
+ time_t start, finish;
+ int left, op, right, result;
+ char line[80];
+
+ right = left = result = 0;
+ op = keys[random() % nkeys];
+ if (op != '/')
+ right = getrandom(rangemax + 1, op, 1);
+retry:
+ /* Get the operands. */
+ switch (op) {
+ case '+':
+ left = getrandom(rangemax + 1, op, 0);
+ result = left + right;
+ break;
+ case '-':
+ result = getrandom(rangemax + 1, op, 0);
+ left = right + result;
+ break;
+ case 'x':
+ left = getrandom(rangemax + 1, op, 0);
+ result = left * right;
+ break;
+ case '/':
+ right = getrandom(rangemax, op, 1) + 1;
+ result = getrandom(rangemax + 1, op, 0);
+ left = right * result + random() % right;
+ break;
+ }
+
+ /*
+ * A very big maxrange could cause negative values to pop
+ * up, owing to overflow.
+ */
+ if (result < 0 || left < 0)
+ goto retry;
+
+ (void)printf("%d %c %d = ", left, op, right);
+ (void)fflush(stdout);
+ (void)time(&start);
+
+ /*
+ * Keep looping until the correct answer is given, or until EOF or
+ * interrupt is typed.
+ */
+ for (;;) {
+ if (!fgets(line, sizeof(line), stdin)) {
+ (void)printf("\n");
+ return(EOF);
+ }
+ for (p = line; *p && isspace((unsigned char)*p); ++p);
+ if (!isdigit((unsigned char)*p)) {
+ (void)printf("Please type a number.\n");
+ continue;
+ }
+ if (atoi(p) == result) {
+ (void)printf("Right!\n");
+ ++nright;
+ break;
+ }
+ /* Wrong answer; penalise and ask again. */
+ (void)printf("What?\n");
+ ++nwrong;
+ penalise(right, op, 1);
+ if (op == 'x' || op == '+')
+ penalise(left, op, 0);
+ else
+ penalise(result, op, 0);
+ }
+
+ /*
+ * Accumulate the time taken. Obviously rounding errors happen here;
+ * however they should cancel out, because some of the time you are
+ * charged for a partially elapsed second at the start, and some of
+ * the time you are not charged for a partially elapsed second at the
+ * end.
+ */
+ (void)time(&finish);
+ qtime += finish - start;
+ return(0);
+}
+
+/*
+ * Here is the code for accumulating penalties against the numbers for which
+ * a wrong answer was given. The right operand and either the left operand
+ * (for +, x) or the result (for -, /) are stored in a list for the particular
+ * operation, and each becomes more likely to appear again in that operation.
+ * Initially, each number is charged a penalty of WRONGPENALTY, giving it that
+ * many extra chances of appearing. Each time it is selected because of this,
+ * its penalty is decreased by one; it is removed when it reaches 0.
+ *
+ * The penalty[] array gives the sum of all penalties in the list for
+ * each operation and each operand. The penlist[] array has the lists of
+ * penalties themselves.
+ */
+
+static int penalty[sizeof(keylist) - 1][2];
+static struct penalty {
+ int value, penalty; /* Penalised value and its penalty. */
+ struct penalty *next;
+} *penlist[sizeof(keylist) - 1][2];
+
+#define WRONGPENALTY 5 /* Perhaps this should depend on maxrange. */
+
+/*
+ * Add a penalty for the number `value' to the list for operation `op',
+ * operand number `operand' (0 or 1). If we run out of memory, we just
+ * forget about the penalty (how likely is this, anyway?).
+ */
+static void
+penalise(int value, int op, int operand)
+{
+ struct penalty *p;
+
+ op = opnum(op);
+ if ((p = malloc(sizeof(*p))) == NULL)
+ return;
+ p->next = penlist[op][operand];
+ penlist[op][operand] = p;
+ penalty[op][operand] += p->penalty = WRONGPENALTY;
+ p->value = value;
+}
+
+/*
+ * Select a random value from 0 to maxval - 1 for operand `operand' (0 or 1)
+ * of operation `op'. The random number we generate is either used directly
+ * as a value, or represents a position in the penalty list. If the latter,
+ * we find the corresponding value and return that, decreasing its penalty.
+ */
+static int
+getrandom(int maxval, int op, int operand)
+{
+ int value;
+ struct penalty **pp, *p;
+
+ op = opnum(op);
+ value = random() % (maxval + penalty[op][operand]);
+
+ /*
+ * 0 to maxval - 1 is a number to be used directly; bigger values
+ * are positions to be located in the penalty list.
+ */
+ if (value < maxval)
+ return(value);
+ value -= maxval;
+
+ /*
+ * Find the penalty at position `value'; decrement its penalty and
+ * delete it if it reaches 0; return the corresponding value.
+ */
+ for (pp = &penlist[op][operand]; (p = *pp) != NULL; pp = &p->next) {
+ if (p->penalty > value) {
+ value = p->value;
+ penalty[op][operand]--;
+ if (--(p->penalty) <= 0) {
+ p = p->next;
+ (void)free((char *)*pp);
+ *pp = p;
+ }
+ return(value);
+ }
+ value -= p->penalty;
+ }
+ /*
+ * We can only get here if the value from the penalty[] array doesn't
+ * correspond to the actual sum of penalties in the list. Provide an
+ * obscure message.
+ */
+ errx(1, "arithmetic: bug: inconsistent penalties.");
+ /* NOTREACHED */
+}
+
+/* Return an index for the character op, which is one of [+-x/]. */
+static int
+opnum(int op)
+{
+ char *p;
+
+ if (op == 0 || (p = strchr(keylist, op)) == NULL)
+ errx(1, "arithmetic: bug: op %c not in keylist %s",
+ op, keylist);
+ return(p - keylist);
+}
+
+/* Print usage message and quit. */
+static void
+usage(void)
+{
+ (void)fprintf(stderr, "Usage: %s [-o +-x/] [-r range]\n",
+ getprogname());
+ exit(1);
+}