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/* Copyright (C) 2014-2020 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>. */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <assert.h>
#include <math.h>
bool is_prime(unsigned n)
{
assert(n > 1);
if (n <= 3)
return true;
if (!(n & 1))
return false;
if (n % 3 == 0)
return false;
unsigned lim = unsigned(sqrt((double)n));
unsigned d = 5;
for (;;) {
if (d > lim)
break;
if (n % d == 0)
return false;
d += 2;
if (d > lim)
break;
if (n % d == 0)
return false;
d += 4;
}
return true;
}
// Local Variables:
// fill-column: 72
// mode: C++
// End:
// vim: set cindent noexpandtab shiftwidth=2 textwidth=72:
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