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/*
Copyright (C) 2014 Fredrik Johansson
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 "acb.h"
void
acb_chebyshev_t_ui(acb_t y, ulong n, const acb_t x, slong prec)
{
int i, r;
if (n <= 1)
{
if (n == 0)
acb_one(y);
else
acb_set_round(y, x, prec);
return;
}
r = flint_ctz(n);
if ((n >> r) == 1)
{
acb_mul(y, x, x, prec);
acb_mul_2exp_si(y, y, 1);
acb_sub_ui(y, y, 1, prec);
r -= 1;
}
else
{
/* we only need one value, so break out final iteration */
acb_t t, u;
acb_init(t);
acb_init(u);
acb_chebyshev_t2_ui(t, u, (n >> (r + 1)) + 1, x, prec);
acb_mul(t, t, u, prec);
acb_mul_2exp_si(t, t, 1);
acb_sub(y, t, x, prec);
acb_clear(t);
acb_clear(u);
}
for (i = 0; i < r; i++)
{
acb_mul(y, y, y, prec);
acb_mul_2exp_si(y, y, 1);
acb_sub_ui(y, y, 1, prec);
}
}