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/* Copyright (C) 2014 Free Software Foundation, Inc.
This file is part of groff.
groff is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation, either version 2 of the License, or
(at your option) any later version.
groff is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
The GNU General Public License version 2 (GPL2) is available in the
internet at <http://www.gnu.org/licenses/gpl-2.0.txt>. */
#include <math.h>
int is_prime(unsigned n)
{
if (n <= 3)
return 1;
if (!(n & 1))
return 0;
if (n % 3 == 0)
return 0;
unsigned lim = unsigned(sqrt((double)n));
unsigned d = 5;
for (;;) {
if (d > lim)
break;
if (n % d == 0)
return 0;
d += 2;
if (d > lim)
break;
if (n % d == 0)
return 0;
d += 4;
}
return 1;
}
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