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Diffstat (limited to 'games/factor/factor.c')
| -rw-r--r-- | games/factor/factor.c | 201 |
1 files changed, 201 insertions, 0 deletions
diff --git a/games/factor/factor.c b/games/factor/factor.c new file mode 100644 index 0000000..562e4b2 --- /dev/null +++ b/games/factor/factor.c @@ -0,0 +1,201 @@ +/* + * Copyright (c) 1989, 1993 + * The Regents of the University of California. All rights reserved. + * + * This code is derived from software contributed to Berkeley by + * Landon Curt Noll. + * + * 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. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 4. 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. + */ + +#ifndef lint +static char copyright[] = +"@(#) Copyright (c) 1989, 1993\n\ + The Regents of the University of California. All rights reserved.\n"; +#endif /* not lint */ + +#ifndef lint +static char sccsid[] = "@(#)factor.c 8.3 (Berkeley) 3/30/94"; +#endif /* not lint */ + +/* + * factor - factor a number into primes + * + * By: Landon Curt Noll chongo@toad.com, ...!{sun,tolsoft}!hoptoad!chongo + * + * chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\ + * + * usage: + * factor [number] ... + * + * The form of the output is: + * + * number: factor1 factor1 factor2 factor3 factor3 factor3 ... + * + * where factor1 < factor2 < factor3 < ... + * + * If no args are given, the list of numbers are read from stdin. + */ + +#include <err.h> +#include <ctype.h> +#include <errno.h> +#include <limits.h> +#include <stdio.h> +#include <stdlib.h> + +#include "primes.h" + +/* + * prime[i] is the (i-1)th prime. + * + * We are able to sieve 2^32-1 because this byte table yields all primes + * up to 65537 and 65537^2 > 2^32-1. + */ +extern ubig prime[]; +extern ubig *pr_limit; /* largest prime in the prime array */ + +void pr_fact __P((ubig)); /* print factors of a value */ +void usage __P((void)); + +int +main(argc, argv) + int argc; + char *argv[]; +{ + ubig val; + int ch; + char *p, buf[100]; /* > max number of digits. */ + + while ((ch = getopt(argc, argv, "")) != EOF) + switch (ch) { + case '?': + default: + usage(); + } + argc -= optind; + argv += optind; + + /* No args supplied, read numbers from stdin. */ + if (argc == 0) + for (;;) { + if (fgets(buf, sizeof(buf), stdin) == NULL) { + if (ferror(stdin)) + err(1, "stdin"); + exit (0); + } + for (p = buf; isblank(*p); ++p); + if (*p == '\n' || *p == '\0') + continue; + if (*p == '-') + errx(1, "negative numbers aren't permitted."); + errno = 0; + val = strtoul(buf, &p, 10); + if (errno) + err(1, "%s", buf); + if (*p != '\n') + errx(1, "%s: illegal numeric format.", buf); + pr_fact(val); + } + /* Factor the arguments. */ + else + for (; *argv != NULL; ++argv) { + if (argv[0][0] == '-') + errx(1, "negative numbers aren't permitted."); + errno = 0; + val = strtoul(argv[0], &p, 10); + if (errno) + err(1, "%s", argv[0]); + if (*p != '\0') + errx(1, "%s: illegal numeric format.", argv[0]); + pr_fact(val); + } + exit(0); +} + +/* + * pr_fact - print the factors of a number + * + * If the number is 0 or 1, then print the number and return. + * If the number is < 0, print -1, negate the number and continue + * processing. + * + * Print the factors of the number, from the lowest to the highest. + * A factor will be printed numtiple times if it divides the value + * multiple times. + * + * Factors are printed with leading tabs. + */ +void +pr_fact(val) + ubig val; /* Factor this value. */ +{ + ubig *fact; /* The factor found. */ + + /* Firewall - catch 0 and 1. */ + if (val == 0) /* Historical practice; 0 just exits. */ + exit(0); + if (val == 1) { + (void)printf("1: 1\n"); + return; + } + + /* Factor value. */ + (void)printf("%lu:", val); + for (fact = &prime[0]; val > 1; ++fact) { + /* Look for the smallest factor. */ + do { + if (val % (long)*fact == 0) + break; + } while (++fact <= pr_limit); + + /* Watch for primes larger than the table. */ + if (fact > pr_limit) { + (void)printf(" %lu", val); + break; + } + + /* Divide factor out until none are left. */ + do { + (void)printf(" %lu", *fact); + val /= (long)*fact; + } while ((val % (long)*fact) == 0); + + /* Let the user know we're doing something. */ + (void)fflush(stdout); + } + (void)putchar('\n'); +} + +void +usage() +{ + (void)fprintf(stderr, "usage: factor [value ...]\n"); + exit (0); +} |
