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WebSVN – planix.SVN – Blame – /os/branches/feature_unix/sys/src/cmd/factor.c – Rev 2

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#include <u.h>
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#include <libc.h>
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#include <bio.h>
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#define	whsiz	(sizeof(wheel)/sizeof(wheel[0]))
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double	wheel[] =
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{
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	 2,10, 2, 4, 2, 4, 6, 2, 6, 4,
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	 2, 4, 6, 6, 2, 6, 4, 2, 6, 4,
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	 6, 8, 4, 2, 4, 2, 4, 8, 6, 4,
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	 6, 2, 4, 6, 2, 6, 6, 4, 2, 4,
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	 6, 2, 6, 4, 2, 4, 2,10,
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};
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Biobuf	bin;
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void	factor(double);
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void
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main(int argc, char *argv[])
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{
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	double n;
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	int i;
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	char *l;
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	if(argc > 1) {
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		for(i=1; i<argc; i++) {
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			n = atof(argv[i]);
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			factor(n);
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		}
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		exits(0);
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	}
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	Binit(&bin, 0, OREAD);
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	for(;;) {
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		l = Brdline(&bin, '\n');
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		if(l ==  0)
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			break;
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		n = atof(l);
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		if(n <= 0)
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			break;
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		factor(n);
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	}
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	exits(0);
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}
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void
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factor(double n)
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{
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	double quot, d, s;
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	int i;
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	print("%.0f\n", n);
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	if(n == 0)
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		return;
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	s = sqrt(n) + 1;
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	while(modf(n/2, &quot) == 0) {
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		print("     2\n");
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		n = quot;
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		s = sqrt(n) + 1;
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	}
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	while(modf(n/3, &quot) == 0) {
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		print("     3\n");
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		n = quot;
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		s = sqrt(n) + 1;
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	}
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	while(modf(n/5, &quot) == 0) {
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		print("     5\n");
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		n = quot;
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		s = sqrt(n) + 1;
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	}
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	while(modf(n/7, &quot) == 0) {
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		print("     7\n");
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		n = quot;
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		s = sqrt(n) + 1;
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	}
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	d = 1;
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	for(i=1;;) {
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		d += wheel[i];
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		while(modf(n/d, &quot) == 0) {
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			print("     %.0f\n", d);
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			n = quot;
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			s = sqrt(n) + 1;
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		}
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		i++;
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		if(i >= whsiz) {
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			i = 0;
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			if(d > s)
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				break;
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		}
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	}
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	if(n > 1)
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		print("     %.0f\n",n);
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	print("\n");
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}