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/*
Copyright (C) 2009 William Hart
This file is part of FLINT.
FLINT is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 3 of the License, or
(at your option) any later version. See <https://www.gnu.org/licenses/>.
*/
#include "ulong_extras.h"
ulong
n_mod2_precomp(ulong a, ulong n, double npre)
{
ulong quot;
slong rem;
if (a < n)
return a;
if ((slong) n < WORD(0))
return a - n;
if (n == 1)
{
quot = a;
rem = 0;
} else
{
quot = (ulong) ((double) a * npre);
rem = a - quot * n;
}
if (rem < (slong) (-n))
quot -= (ulong) ((double) (-rem) * npre);
else if (rem >= (slong) n)
quot += (ulong) ((double) rem * npre);
else if (rem < WORD(0))
return rem + n;
else
return rem;
rem = a - quot * n;
if (rem >= (slong) n)
return rem - n;
else if (rem < WORD(0))
return rem + n;
else
return rem;
}