Retro68/gcc/libquadmath/math/cacoshq.c

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/* Return arc hyperbole cosine for __float128 value.
Copyright (C) 1997, 1998, 2006 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, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include "quadmath-imp.h"
__complex128
cacoshq (__complex128 x)
{
__complex128 res;
int rcls = fpclassifyq (__real__ x);
int icls = fpclassifyq (__imag__ x);
if (rcls <= QUADFP_INFINITE || icls <= QUADFP_INFINITE)
{
if (icls == QUADFP_INFINITE)
{
__real__ res = HUGE_VALQ;
if (rcls == QUADFP_NAN)
__imag__ res = nanq ("");
else
__imag__ res = copysignq ((rcls == QUADFP_INFINITE
? (__real__ x < 0.0
? M_PIq - M_PI_4q : M_PI_4q)
: M_PI_2q), __imag__ x);
}
else if (rcls == QUADFP_INFINITE)
{
__real__ res = HUGE_VALQ;
if (icls >= QUADFP_ZERO)
__imag__ res = copysignq (signbitq (__real__ x) ? M_PIq : 0.0,
__imag__ x);
else
__imag__ res = nanq ("");
}
else
{
__real__ res = nanq ("");
__imag__ res = nanq ("");
}
}
else if (rcls == QUADFP_ZERO && icls == QUADFP_ZERO)
{
__real__ res = 0.0;
__imag__ res = copysignq (M_PI_2q, __imag__ x);
}
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/* The factor 16 is just a guess. */
else if (16.0Q * fabsq (__imag__ x) < fabsq (__real__ x))
{
/* Kahan's formula which avoid cancellation through subtraction in
some cases. */
res = 2.0Q * clogq (csqrtq ((x + 1.0Q) / 2.0Q)
+ csqrtq ((x - 1.0Q) / 2.0Q));
if (signbitq (__real__ res))
__real__ res = 0.0Q;
}
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else
{
__complex128 y;
__real__ y = (__real__ x - __imag__ x) * (__real__ x + __imag__ x) - 1.0;
__imag__ y = 2.0 * __real__ x * __imag__ x;
y = csqrtq (y);
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if (signbitq (x))
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y = -y;
__real__ y += __real__ x;
__imag__ y += __imag__ x;
res = clogq (y);
}
return res;
}