1/* Return arc hyperbole cosine for __float128 value.
2 Copyright (C) 1997, 1998, 2006 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 "quadmath-imp.h"
22
23
24__complex128
25cacoshq (__complex128 x)
26{
27 __complex128 res;
28 int rcls = fpclassifyq (__real__ x);
29 int icls = fpclassifyq (__imag__ x);
30
31 if (rcls <= QUADFP_INFINITE || icls <= QUADFP_INFINITE)
32 {
33 if (icls == QUADFP_INFINITE)
34 {
35 __real__ res = HUGE_VALQ;
36
37 if (rcls == QUADFP_NAN)
38 __imag__ res = nanq ("");
39 else
40 __imag__ res = copysignq ((rcls == QUADFP_INFINITE
41 ? (__real__ x < 0.0
42 ? M_PIq - M_PI_4q : M_PI_4q)
43 : M_PI_2q), __imag__ x);
44 }
45 else if (rcls == QUADFP_INFINITE)
46 {
47 __real__ res = HUGE_VALQ;
48
49 if (icls >= QUADFP_ZERO)
50 __imag__ res = copysignq (signbitq (__real__ x) ? M_PIq : 0.0,
51 __imag__ x);
52 else
53 __imag__ res = nanq ("");
54 }
55 else
56 {
57 __real__ res = nanq ("");
58 __imag__ res = nanq ("");
59 }
60 }
61 else if (rcls == QUADFP_ZERO && icls == QUADFP_ZERO)
62 {
63 __real__ res = 0.0;
64 __imag__ res = copysignq (M_PI_2q, __imag__ x);
65 }
66 /* The factor 16 is just a guess. */
67 else if (16.0Q * fabsq (__imag__ x) < fabsq (__real__ x))
68 {
69 /* Kahan's formula which avoid cancellation through subtraction in
70 some cases. */
71 res = 2.0Q * clogq (csqrtq ((x + 1.0Q) / 2.0Q)
72 + csqrtq ((x - 1.0Q) / 2.0Q));
73 if (signbitq (__real__ res))
74 __real__ res = 0.0Q;
75 }
76 else
77 {
78 __complex128 y;
79
80 __real__ y = (__real__ x - __imag__ x) * (__real__ x + __imag__ x) - 1.0;
81 __imag__ y = 2.0 * __real__ x * __imag__ x;
82
83 y = csqrtq (y);
84
85 if (signbitq (x))
86 y = -y;
87
88 __real__ y += __real__ x;
89 __imag__ y += __imag__ x;
90
91 res = clogq (y);
92 }
93
94 return res;
95}
96