mirror of
https://github.com/vale981/arb
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55 lines
1.1 KiB
C
55 lines
1.1 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_u_ui(acb_t y, ulong n, const acb_t x, slong prec)
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{
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acb_t a, b;
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if (n <= 1)
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{
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if (n == 0)
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{
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acb_one(y);
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}
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else
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{
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acb_set_round(y, x, prec);
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acb_mul_2exp_si(y, y, 1);
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}
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return;
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}
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acb_init(a);
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acb_init(b);
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acb_chebyshev_u2_ui(a, b, n / 2, x, prec);
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if (n % 2 == 0)
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{
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acb_add(y, a, b, prec);
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acb_sub(b, a, b, prec);
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acb_mul(y, y, b, prec);
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}
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else
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{
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acb_submul(b, a, x, prec);
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acb_mul(y, a, b, prec);
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acb_mul_2exp_si(y, y, 1);
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acb_neg(y, y);
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}
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acb_clear(a);
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acb_clear(b);
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}
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