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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_u_ui(acb_t y, ulong n, const acb_t x, slong prec)
{
acb_t a, b;
if (n <= 1)
{
if (n == 0)
{
acb_one(y);
}
else
{
acb_set_round(y, x, prec);
acb_mul_2exp_si(y, y, 1);
}
return;
}
acb_init(a);
acb_init(b);
acb_chebyshev_u2_ui(a, b, n / 2, x, prec);
if (n % 2 == 0)
{
acb_add(y, a, b, prec);
acb_sub(b, a, b, prec);
acb_mul(y, y, b, prec);
}
else
{
acb_submul(b, a, x, prec);
acb_mul(y, a, b, prec);
acb_mul_2exp_si(y, y, 1);
acb_neg(y, y);
}
acb_clear(a);
acb_clear(b);
}