diff options
author | Rob Landley <rob@landley.net> | 2014-08-01 09:08:00 -0500 |
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committer | Rob Landley <rob@landley.net> | 2014-08-01 09:08:00 -0500 |
commit | 2a53f53d74167353cf434af59392c72a885cb7f6 (patch) | |
tree | fa64de3c8103b9779d84edfb334973e03265555e /toys | |
parent | b3c2d1cd4ef97f200bb7b668ae4c3be06d59063c (diff) | |
download | toybox-2a53f53d74167353cf434af59392c72a885cb7f6.tar.gz |
Add factor.
I was reading http://www.muppetlabs.com/~breadbox/txt/rsa.html and it mentioned
"factor" and I noticed it was in coreutils. I'm not sure why it's in coreutils,
but it's pretty trivial, so...
Diffstat (limited to 'toys')
-rw-r--r-- | toys/other/factor.c | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/toys/other/factor.c b/toys/other/factor.c new file mode 100644 index 00000000..e3992a8b --- /dev/null +++ b/toys/other/factor.c @@ -0,0 +1,77 @@ +/* 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) +{ + long l, ll; + + l = strtol(s, &s, 0); + if (*s) { + error_msg("%s: not integer"); + return; + } + + printf("%ld:", l); + + // Negative numbers have -1 as a factor + if (l < 0) { + printf(" -1"); + l *= -1; + } + + // Deal with 0 and 1 (and 2 since we're here) + if (l < 3) { + printf(" %ld\n", l); + return; + } + + // Special case factors of 2 + while (l && !(l&1)) { + printf(" 2"); + l >>= 1; + } + + // test odd numbers. + for (ll=3; ;ll += 2) { + if (ll*ll>l) { + if (l>1) printf(" %ld", l); + break; + } + while (!(l%ll)) { + printf(" %ld", 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); + } +} |