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88 lines
1.5 KiB
88 lines
1.5 KiB
/* factor.c - Factor integers
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*
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* Copyright 2014 Rob Landley <rob@landley.net>
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*
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* No standard, but it's in coreutils
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USE_FACTOR(NEWTOY(factor, 0, TOYFLAG_USR|TOYFLAG_BIN))
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config FACTOR
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bool "factor"
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default y
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help
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usage: factor NUMBER...
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Factor integers.
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*/
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#include "toys.h"
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static void factor(char *s)
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{
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unsigned long long l, ll;
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for (;;) {
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char *err = s;
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int dash = 0;
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while(isspace(*s)) s++;
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if (*s=='-') dash = *s++;
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if (!*s) return;
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errno = 0;
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l = strtoull(s, &s, 0);
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if (errno || (*s && !isspace(*s))) {
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error_msg("%s: not integer", err);
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while (*s && !isspace(*s)) s++;
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continue;
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}
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printf("-%llu:"+!dash, l);
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// Negative numbers have -1 as a factor
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if (dash) printf(" -1");
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// Nothing below 4 has factors
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if (l < 4) {
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printf(" %llu\n", l);
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continue;
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}
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// Special case factors of 2
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while (l && !(l&1)) {
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printf(" 2");
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l >>= 1;
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}
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// test odd numbers until square is > remainder or integer wrap.
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for (ll=3; ;ll += 2) {
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long lll = ll*ll;
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if (lll>l || lll<ll) {
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if (l>1) printf(" %llu", l);
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break;
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}
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while (!(l%ll)) {
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printf(" %llu", ll);
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l /= ll;
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}
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}
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xputc('\n');
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}
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}
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void factor_main(void)
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{
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if (toys.optc) {
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char **ss;
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for (ss = toys.optargs; *ss; ss++) factor(*ss);
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} else for (;;) {
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char *s = 0;
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size_t len = 0;
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if (-1 == getline(&s, &len, stdin)) break;
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factor(s);
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}
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}
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