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 |
25 | cacoshq (__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 | |