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