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 errno = 0; 33 l = strtoull(s, &s, 0); 34 if (errno || (*s && !isspace(*s))) { 35 error_msg("%s: not integer", err); 36 while (*s && !isspace(*s)) s++; 37 continue; 38 } 39 40 printf("-%llu:"+!dash, l); 41 42 // Negative numbers have -1 as a factor 43 if (dash) printf(" -1"); 44 45 // Nothing below 4 has factors 46 if (l < 4) { 47 printf(" %llu\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 until square is > remainder or integer wrap. 58 for (ll=3; ;ll += 2) { 59 long lll = ll*ll; 60 61 if (lll>l || lll<ll) { 62 if (l>1) printf(" %llu", l); 63 break; 64 } 65 while (!(l%ll)) { 66 printf(" %llu", ll); 67 l /= ll; 68 } 69 } 70 xputc('\n'); 71 } 72 } 73 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
