Mercurial > hg > toybox
view toys/other/factor.c @ 1410:ee0109c35b34 draft
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...
author | Rob Landley <rob@landley.net> |
---|---|
date | Fri, 01 Aug 2014 09:08:00 -0500 |
parents | |
children | dd336488a69b |
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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) { 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); } }