arb/arb_poly/div_root.c
2015-11-05 17:59:29 +00:00

60 lines
1.7 KiB
C

/*=============================================================================
This file is part of ARB.
ARB 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.
ARB 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 ARB; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2011 William Hart
Copyright (C) 2012 Fredrik Johansson
******************************************************************************/
#include "arb_poly.h"
void
_arb_poly_div_root(arb_ptr Q, arb_t R, arb_srcptr A,
slong len, const arb_t c, slong prec)
{
arb_t r, t;
slong i;
if (len < 2)
{
arb_zero(R);
return;
}
arb_init(r);
arb_init(t);
arb_set(t, A + len - 2);
arb_set(Q + len - 2, A + len - 1);
arb_set(r, Q + len - 2);
/* TODO: avoid the extra assignments (but still support aliasing) */
for (i = len - 2; i > 0; i--)
{
arb_mul(r, r, c, prec);
arb_add(r, r, t, prec);
arb_set(t, A + i - 1);
arb_set(Q + i - 1, r);
}
arb_mul(r, r, c, prec);
arb_add(R, r, t, prec);
}