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/* Return arc hyperbole cosine for long double value.
Copyright (C) 1997-2012 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <complex.h>
#include <math.h>
#include <math_private.h>
__complex__ long double
__cacoshl (__complex__ long double x)
{
__complex__ long double res;
int rcls = fpclassify (__real__ x);
int icls = fpclassify (__imag__ x);
if (rcls <= FP_INFINITE || icls <= FP_INFINITE)
{
if (icls == FP_INFINITE)
{
__real__ res = HUGE_VALL;
if (rcls == FP_NAN)
__imag__ res = __nanl ("");
else
__imag__ res = __copysignl ((rcls == FP_INFINITE
? (__real__ x < 0.0
? M_PIl - M_PI_4l : M_PI_4l)
: M_PI_2l), __imag__ x);
}
else if (rcls == FP_INFINITE)
{
__real__ res = HUGE_VALL;
if (icls >= FP_ZERO)
__imag__ res = __copysignl (signbit (__real__ x) ? M_PIl : 0.0,
__imag__ x);
else
__imag__ res = __nanl ("");
}
else
{
__real__ res = __nanl ("");
__imag__ res = __nanl ("");
}
}
else if (rcls == FP_ZERO && icls == FP_ZERO)
{
__real__ res = 0.0;
__imag__ res = __copysignl (M_PI_2l, __imag__ x);
}
/* The factor 16 is just a guess. */
else if (16.0L * fabsl (__imag__ x) < fabsl (__real__ x))
{
/* Kahan's formula which avoid cancellation through subtraction in
some cases. */
res = 2.0L * __clogl (__csqrtl ((x + 1.0L) / 2.0L)
+ __csqrtl ((x - 1.0L) / 2.0L));
if (signbit (__real__ res))
__real__ res = 0.0L;
}
else
{
__complex__ long double y;
__real__ y = (__real__ x - __imag__ x) * (__real__ x + __imag__ x) - 1.0;
__imag__ y = 2.0 * __real__ x * __imag__ x;
y = __csqrtl (y);
if (signbit (__real__ x))
y = -y;
__real__ y += __real__ x;
__imag__ y += __imag__ x;
res = __clogl (y);
}
return res;
}
weak_alias (__cacoshl, cacoshl)
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