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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 "gmpcompat.h"
#include "ulong_extras.h"
#include "fmpz.h"
int
fmpz_divides(fmpz_t q, const fmpz_t g, const fmpz_t h)
{
fmpz c1 = *g;
fmpz c2 = *h;
int res, negate = 0;
if (fmpz_is_zero(h))
{
res = fmpz_is_zero(g);
fmpz_zero(q);
return res;
}
if (!COEFF_IS_MPZ(c1)) /* g is small */
{
if (!COEFF_IS_MPZ(c2)) /* h is also small */
{
ulong qz;
if (c1 < 0)
{
c1 = -c1;
negate ^= 1;
}
if (c2 < 0)
{
c2 = -c2;
negate ^= 1;
}
res = n_divides(&qz, c1, c2);
fmpz_set_ui(q, qz);
if (negate)
fmpz_neg(q, q);
return res;
}
else /* h is large and g is small */
{
res = fmpz_is_zero(g);
fmpz_zero(q);
return res;
}
}
else /* g is large */
{
mpz_ptr mq;
if (!COEFF_IS_MPZ(c2)) /* h is small */
{
ulong r;
mq = _fmpz_promote(q);
if (c2 < 0)
{
c2 = -c2;
negate ^= 1;
}
r = flint_mpz_tdiv_q_ui(mq, COEFF_TO_PTR(c1), c2);
res = (r == 0);
if (negate)
mpz_neg(mq, mq);
if (!res)
mpz_set_ui(mq, 0);
_fmpz_demote_val(q);
}
else /* both are large */
{
fmpz_t r;
fmpz_init(r);
fmpz_tdiv_qr(q, r, g, h);
res = fmpz_is_zero(r);
if (!res)
fmpz_zero(q);
fmpz_clear(r);
}
return res;
}
}