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/*=============================================================================
This file is part of FLINT.
FLINT 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.
FLINT 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.
You should have received a copy of the GNU General Public License
along with FLINT; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2011 Fredrik Johansson
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "nmod_vec.h"
#include "nmod_poly.h"
mp_limb_t
_nmod_poly_div_root(mp_ptr Q, mp_srcptr A, slong len, mp_limb_t c, nmod_t mod)
{
mp_limb_t r, t;
slong i;
if (len < 2)
return UWORD(0);
t = A[len - 2];
r = Q[len - 2] = A[len - 1];
for (i = len - 2; i > 0; i--)
{
r = nmod_add(nmod_mul(r, c, mod), t, mod);
t = A[i-1];
Q[i-1] = r;
}
r = nmod_add(nmod_mul(r, c, mod), t, mod);
return r;
}
mp_limb_t
nmod_poly_div_root(nmod_poly_t Q,
const nmod_poly_t A, mp_limb_t c)
{
mp_limb_t rem;
slong len = A->length;
if (len == 0)
{
nmod_poly_zero(Q);
return UWORD(0);
}
if (len == 1)
{
rem = A->coeffs[0];
nmod_poly_zero(Q);
return rem;
}
if (c == 0)
{
rem = A->coeffs[0];
nmod_poly_shift_right(Q, A, 1);
return rem;
}
nmod_poly_fit_length(Q, len - 1);
rem = _nmod_poly_div_root(Q->coeffs, A->coeffs, len, c, Q->mod);
Q->length = len - 1;
return rem;
}
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