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Initial import from FreeBSD RELENG_4:
[dragonfly.git]
/
contrib
/
groff
/
src
/
libs
/
libgroff
/
prime.cc
1
#include <math.h>
2
3
int is_prime(unsigned n)
4
{
5
if (n <= 3)
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return 1;
7
if (!(n & 1))
8
return 0;
9
if (n % 3 == 0)
10
return 0;
11
unsigned lim = unsigned(sqrt((double)n));
12
unsigned d = 5;
13
for (;;) {
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if (d > lim)
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break;
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if (n % d == 0)
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return 0;
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d += 2;
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if (d > lim)
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break;
21
if (n % d == 0)
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return 0;
23
d += 4;
24
}
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return 1;
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}