1/* Return arc hyperbole cosine for double value.
2   Copyright (C) 1997 Free Software Foundation, Inc.
3   This file is part of the GNU C Library.
4   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
5
6   The GNU C Library is free software; you can redistribute it and/or
7   modify it under the terms of the GNU Lesser General Public
8   License as published by the Free Software Foundation; either
9   version 2.1 of the License, or (at your option) any later version.
10
11   The GNU C Library is distributed in the hope that it will be useful,
12   but WITHOUT ANY WARRANTY; without even the implied warranty of
13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14   Lesser General Public License for more details.
15
16   You should have received a copy of the GNU Lesser General Public
17   License along with the GNU C Library; if not, write to the Free
18   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
19   02111-1307 USA.  */
20
21#include <complex.h>
22#include <math.h>
23
24
25__complex__ double
26__cacosh (__complex__ double x)
27{
28  __complex__ double res;
29  int rcls = fpclassify (__real__ x);
30  int icls = fpclassify (__imag__ x);
31
32  if (rcls <= FP_INFINITE || icls <= FP_INFINITE)
33    {
34      if (icls == FP_INFINITE)
35	{
36	  __real__ res = HUGE_VAL;
37
38	  if (rcls == FP_NAN)
39	    __imag__ res = nan ("");
40	  else
41	    __imag__ res = copysign ((rcls == FP_INFINITE
42					? (__real__ x < 0.0
43					   ? M_PI - M_PI_4 : M_PI_4)
44					: M_PI_2), __imag__ x);
45	}
46      else if (rcls == FP_INFINITE)
47	{
48	  __real__ res = HUGE_VAL;
49
50	  if (icls >= FP_ZERO)
51	    __imag__ res = copysign (signbit (__real__ x) ? M_PI : 0.0,
52				       __imag__ x);
53	  else
54	    __imag__ res = nan ("");
55	}
56      else
57	{
58	  __real__ res = nan ("");
59	  __imag__ res = nan ("");
60	}
61    }
62  else if (rcls == FP_ZERO && icls == FP_ZERO)
63    {
64      __real__ res = 0.0;
65      __imag__ res = copysign (M_PI_2, __imag__ x);
66    }
67  else
68    {
69      __complex__ double y;
70
71      __real__ y = (__real__ x - __imag__ x) * (__real__ x + __imag__ x) - 1.0;
72      __imag__ y = 2.0 * __real__ x * __imag__ x;
73
74      y = __csqrt (y);
75
76      __real__ y += __real__ x;
77      __imag__ y += __imag__ x;
78
79      res = __clog (y);
80    }
81
82  return res;
83}
84weak_alias (__cacosh, cacosh)
85#ifdef NO_LONG_DOUBLE
86strong_alias (__cacosh, __cacoshl)
87weak_alias (__cacosh, cacoshl)
88#endif
89