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/*
Copyright (C) 2013 Fredrik Johansson
This file is part of Arb.
Arb 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 2.1 of the License, or
(at your option) any later version. See <http://www.gnu.org/licenses/>.
*/
#include "arb_poly.h"
void
_arb_poly_evaluate2_horner(arb_t y, arb_t z, arb_srcptr poly,
slong len, const arb_t x, slong prec)
{
if (len == 0)
{
arb_zero(y);
arb_zero(z);
}
else if (len == 1)
{
arb_set_round(y, poly + 0, prec);
arb_zero(z);
}
else if (arb_is_zero(x))
{
arb_set_round(y, poly + 0, prec);
arb_set_round(z, poly + 1, prec);
}
else if (len == 2)
{
arb_mul(y, x, poly + 1, prec);
arb_add(y, y, poly + 0, prec);
arb_set_round(z, poly + 1, prec);
}
else
{
arb_t t, u, v;
slong i;
arb_init(t);
arb_init(u);
arb_init(v);
arb_set_round(u, poly + len - 1, prec);
arb_zero(v);
for (i = len - 2; i >= 0; i--)
{
arb_mul(t, v, x, prec);
arb_add(v, u, t, prec);
arb_mul(t, u, x, prec);
arb_add(u, t, poly + i, prec);
}
arb_swap(y, u);
arb_swap(z, v);
arb_clear(t);
arb_clear(u);
arb_clear(v);
}
}
void
arb_poly_evaluate2_horner(arb_t r, arb_t s, const arb_poly_t f, const arb_t a, slong prec)
{
_arb_poly_evaluate2_horner(r, s, f->coeffs, f->length, a, prec);
}
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