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101 lines
2.6 KiB
C
101 lines
2.6 KiB
C
/* Return arc hyperbole cosine for double value.
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Copyright (C) 1997-2012 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <complex.h>
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#include <math.h>
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#include <math_private.h>
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__complex__ double
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__cacosh (__complex__ double x)
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{
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__complex__ double res;
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int rcls = fpclassify (__real__ x);
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int icls = fpclassify (__imag__ x);
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if (rcls <= FP_INFINITE || icls <= FP_INFINITE)
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{
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if (icls == FP_INFINITE)
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{
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__real__ res = HUGE_VAL;
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if (rcls == FP_NAN)
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__imag__ res = __nan ("");
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else
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__imag__ res = __copysign ((rcls == FP_INFINITE
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? (__real__ x < 0.0
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? M_PI - M_PI_4 : M_PI_4)
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: M_PI_2), __imag__ x);
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}
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else if (rcls == FP_INFINITE)
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{
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__real__ res = HUGE_VAL;
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if (icls >= FP_ZERO)
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__imag__ res = __copysign (signbit (__real__ x) ? M_PI : 0.0,
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__imag__ x);
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else
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__imag__ res = __nan ("");
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}
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else
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{
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__real__ res = __nan ("");
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__imag__ res = __nan ("");
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}
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}
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else if (rcls == FP_ZERO && icls == FP_ZERO)
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{
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__real__ res = 0.0;
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__imag__ res = __copysign (M_PI_2, __imag__ x);
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}
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/* The factor 16 is just a guess. */
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else if (16.0 * fabs (__imag__ x) < fabs (__real__ x))
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{
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/* Kahan's formula which avoid cancellation through subtraction in
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some cases. */
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res = 2.0 * __clog (__csqrt ((x + 1.0) / 2.0) + __csqrt ((x - 1.0) / 2.0));
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if (signbit (__real__ res))
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__real__ res = 0.0;
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}
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else
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{
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__complex__ double y;
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__real__ y = (__real__ x - __imag__ x) * (__real__ x + __imag__ x) - 1.0;
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__imag__ y = 2.0 * __real__ x * __imag__ x;
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y = __csqrt (y);
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if (signbit (__real__ x))
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y = -y;
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__real__ y += __real__ x;
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__imag__ y += __imag__ x;
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res = __clog (y);
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}
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return res;
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}
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weak_alias (__cacosh, cacosh)
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#ifdef NO_LONG_DOUBLE
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strong_alias (__cacosh, __cacoshl)
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weak_alias (__cacosh, cacoshl)
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#endif
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