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1410
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1 /* factor.c - Factor integers
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2 *
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3 * Copyright 2014 Rob Landley <rob@landley.net>
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4 *
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5 * No standard, but it's in coreutils
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6
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7 USE_FACTOR(NEWTOY(factor, 0, TOYFLAG_USR|TOYFLAG_BIN))
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8
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9 config FACTOR
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10 bool "factor"
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11 default y
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12 help
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13 usage: factor NUMBER...
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14
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15 Factor integers.
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16 */
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17
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18 #include "toys.h"
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19
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20 static void factor(char *s)
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21 {
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22 long l, ll;
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23
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24 l = strtol(s, &s, 0);
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25 if (*s) {
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26 error_msg("%s: not integer");
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27 return;
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28 }
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29
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30 printf("%ld:", l);
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31
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32 // Negative numbers have -1 as a factor
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33 if (l < 0) {
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34 printf(" -1");
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35 l *= -1;
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36 }
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37
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38 // Deal with 0 and 1 (and 2 since we're here)
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39 if (l < 3) {
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40 printf(" %ld\n", l);
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41 return;
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42 }
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43
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44 // Special case factors of 2
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45 while (l && !(l&1)) {
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46 printf(" 2");
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47 l >>= 1;
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48 }
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49
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50 // test odd numbers.
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51 for (ll=3; ;ll += 2) {
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52 if (ll*ll>l) {
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53 if (l>1) printf(" %ld", l);
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54 break;
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55 }
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56 while (!(l%ll)) {
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57 printf(" %ld", ll);
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58 l /= ll;
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59 }
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60 }
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61 xputc('\n');
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62 }
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63
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64 void factor_main(void)
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65 {
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66 if (toys.optc) {
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67 char **ss;
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68
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69 for (ss = toys.optargs; *ss; ss++) factor(*ss);
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70 } else for (;;) {
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71 char *s = 0;
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72 size_t len = 0;
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73
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74 if (-1 == getline(&s, &len, stdin)) break;
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75 factor(s);
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76 }
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77 }
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