9base

revived minimalist port of Plan 9 userland to Unix
git clone git://git.suckless.org/9base
Log | Files | Refs | README | LICENSE

factor.c (1348B)

      1 #include <u.h>
      2 #include <libc.h>
      3 #include <bio.h>
      4 
      5 #define	whsiz	(sizeof(wheel)/sizeof(wheel[0]))
      6 
      7 double	wheel[] =
      8 {
      9 	 2,10, 2, 4, 2, 4, 6, 2, 6, 4,
     10 	 2, 4, 6, 6, 2, 6, 4, 2, 6, 4,
     11 	 6, 8, 4, 2, 4, 2, 4, 8, 6, 4,
     12 	 6, 2, 4, 6, 2, 6, 6, 4, 2, 4,
     13 	 6, 2, 6, 4, 2, 4, 2,10,
     14 };
     15 
     16 Biobuf	bin;
     17 
     18 void	factor(double);
     19 
     20 void
     21 main(int argc, char *argv[])
     22 {
     23 	double n;
     24 	int i;
     25 	char *l;
     26 
     27 	if(argc > 1) {
     28 		for(i=1; i<argc; i++) {
     29 			n = atof(argv[i]);
     30 			factor(n);
     31 		}
     32 		exits(0);
     33 	}
     34 
     35 	Binit(&bin, 0, OREAD);
     36 	for(;;) {
     37 		l = Brdline(&bin, '\n');
     38 		if(l ==  0)
     39 			break;
     40 		n = atof(l);
     41 		if(n <= 0)
     42 			break;
     43 		factor(n);
     44 	}
     45 	exits(0);
     46 }
     47 
     48 void
     49 factor(double n)
     50 {
     51 	double quot, d, s;
     52 	int i;
     53 
     54 	print("%.0f\n", n);
     55 	if(n == 0)
     56 		return;
     57 	s = sqrt(n) + 1;
     58 	while(modf(n/2, &quot) == 0) {
     59 		print("     2\n");
     60 		n = quot;
     61 		s = sqrt(n) + 1;
     62 	}
     63 	while(modf(n/3, &quot) == 0) {
     64 		print("     3\n");
     65 		n = quot;
     66 		s = sqrt(n) + 1;
     67 	}
     68 	while(modf(n/5, &quot) == 0) {
     69 		print("     5\n");
     70 		n = quot;
     71 		s = sqrt(n) + 1;
     72 	}
     73 	while(modf(n/7, &quot) == 0) {
     74 		print("     7\n");
     75 		n = quot;
     76 		s = sqrt(n) + 1;
     77 	}
     78 	d = 1;
     79 	for(i=1;;) {
     80 		d += wheel[i];
     81 		while(modf(n/d, &quot) == 0) {
     82 			print("     %.0f\n", d);
     83 			n = quot;
     84 			s = sqrt(n) + 1;
     85 		}
     86 		i++;
     87 		if(i >= whsiz) {
     88 			i = 0;
     89 			if(d > s)
     90 				break;
     91 		}
     92 	}
     93 	if(n > 1)
     94 		print("     %.0f\n",n);
     95 	print("\n");
     96 }