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https://github.com/vale981/arb
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51 lines
1.2 KiB
C
51 lines
1.2 KiB
C
/*
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Copyright (C) 2014 Fredrik Johansson
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This file is part of Arb.
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Arb is free software: you can redistribute it and/or modify it under
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the terms of the GNU Lesser General Public License (LGPL) as published
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by the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version. See <http://www.gnu.org/licenses/>.
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*/
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#include "acb.h"
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void
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acb_chebyshev_t2_ui(acb_t a, acb_t b, ulong n, const acb_t x, slong prec)
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{
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int i;
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acb_set_round(a, x, prec);
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acb_one(b);
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if (n <= 1)
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{
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if (n == 0)
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acb_swap(a, b);
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return;
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}
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for (i = FLINT_BIT_COUNT(n - 1) - 1; i >= 0; i--)
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{
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if (((n - 1) >> i) & 1)
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{
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acb_mul(b, b, a, prec);
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acb_mul_2exp_si(b, b, 1);
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acb_sub(b, b, x, prec);
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acb_mul(a, a, a, prec);
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acb_mul_2exp_si(a, a, 1);
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acb_sub_ui(a, a, 1, prec);
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}
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else
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{
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acb_mul(a, a, b, prec);
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acb_mul_2exp_si(a, a, 1);
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acb_sub(a, a, x, prec);
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acb_mul(b, b, b, prec);
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acb_mul_2exp_si(b, b, 1);
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acb_sub_ui(b, b, 1, prec);
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}
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}
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}
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