1 /* factor.c - Factor integers 2 * 3 * Copyright 2014 Rob Landley <rob (at) 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 20 static void factor(char *s) 21 { 22 unsigned long long l, ll; 23 24 for (;;) { 25 char *err = s; 26 int dash = 0; 27 28 while(isspace(*s)) s++; 29 if (*s=='-') dash = *s++; 30 if (!*s) return; 31 32 l = strtoull(s, &s, 0); 33 if (*s && !isspace(*s)) { 34 error_msg("%s: not integer", err); 35 while (*s && !isspace(*s)) s++; 36 continue; 37 } 38 39 printf("-%llu:"+!dash, l); 40 41 // Negative numbers have -1 as a factor 42 if (dash) printf(" -1"); 43 44 // Nothing below 4 has factors 45 if (l < 4) { 46 printf(" %llu\n", l); 47 continue; 48 } 49 50 // Special case factors of 2 51 while (l && !(l&1)) { 52 printf(" 2"); 53 l >>= 1; 54 } 55 56 // test odd numbers until square is > remainder or integer wrap. 57 for (ll=3; ;ll += 2) { 58 long lll = ll*ll; 59 60 if (lll>l || lll<ll) { 61 if (l>1) printf(" %llu", l); 62 break; 63 } 64 while (!(l%ll)) { 65 printf(" %llu", ll); 66 l /= ll; 67 } 68 } 69 xputc('\n'); 70 } 71 } 72 73 void factor_main(void) 74 { 75 if (toys.optc) { 76 char **ss; 77 78 for (ss = toys.optargs; *ss; ss++) factor(*ss); 79 } else for (;;) { 80 char *s = 0; 81 size_t len = 0; 82 83 if (-1 == getline(&s, &len, stdin)) break; 84 factor(s); 85 } 86 } 87
