1 /* factor.c - Factor integers
2 *
3 * Copyright 2014 Rob Landley <rob@landley.net>
4 *
5 * No standard, but it's in coreutils
6
7 USE_FACTOR(NEWTOY(factor, 0, TOYFLAG_USR|TOYFLAG_BIN))
8
9 config FACTOR
10 bool "factor"
11 default y
12 help
13 usage: factor NUMBER...
14
15 Factor integers.
16 */
17
18 #include "toys.h"
19
factor(char * s)20 static void factor(char *s)
21 {
22 unsigned long l, ll;
23
24 for (;;) {
25 char *err = s;
26
27 while(isspace(*s)) s++;
28 if (!*s) return;
29
30 l = strtoul(s, &s, 0);
31 if (*s && !isspace(*s)) {
32 error_msg("%s: not integer", err);
33
34 return;
35 }
36
37 printf("%lu:", l);
38
39 // Negative numbers have -1 as a factor
40 if (l < 0) {
41 printf(" -1");
42 l *= -1;
43 }
44
45 // Nothing below 4 has factors
46 if (l < 4) {
47 printf(" %lu\n", l);
48 continue;
49 }
50
51 // Special case factors of 2
52 while (l && !(l&1)) {
53 printf(" 2");
54 l >>= 1;
55 }
56
57 // test odd numbers.
58 for (ll=3; ;ll += 2) {
59 long lll = ll*ll;
60
61 if (lll>l || lll<ll) {
62 if (l>1) printf(" %lu", l);
63 break;
64 }
65 while (!(l%ll)) {
66 printf(" %lu", ll);
67 l /= ll;
68 }
69 }
70 xputc('\n');
71 }
72 }
73
factor_main(void)74 void factor_main(void)
75 {
76 if (toys.optc) {
77 char **ss;
78
79 for (ss = toys.optargs; *ss; ss++) factor(*ss);
80 } else for (;;) {
81 char *s = 0;
82 size_t len = 0;
83
84 if (-1 == getline(&s, &len, stdin)) break;
85 factor(s);
86 }
87 }
88