/*
    Copyright (C) 2016 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_taylor_shift_horner(arb_ptr poly, const arb_t c, slong n, slong prec)
{
    slong i, j;

    if (arb_is_one(c))
    {
        for (i = n - 2; i >= 0; i--)
            for (j = i; j < n - 1; j++)
                arb_add(poly + j, poly + j, poly + j + 1, prec);
    }
    else if (arb_equal_si(c, -1))
    {
        for (i = n - 2; i >= 0; i--)
            for (j = i; j < n - 1; j++)
                arb_sub(poly + j, poly + j, poly + j + 1, prec);
    }
    else if (!arb_is_zero(c))
    {
        for (i = n - 2; i >= 0; i--)
            for (j = i; j < n - 1; j++)
                arb_addmul(poly + j, poly + j + 1, c, prec);
    }
}

void
arb_poly_taylor_shift_horner(arb_poly_t g, const arb_poly_t f,
    const arb_t c, slong prec)
{
    if (f != g)
        arb_poly_set_round(g, f, prec);

    _arb_poly_taylor_shift_horner(g->coeffs, c, g->length, prec);
}