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b12676a5 | 1 | /* Return arc hyperbole cosine for __float128 value. |
92920cc6 | 2 | Copyright (C) 1997, 1998, 2006 Free Software Foundation, Inc. |
b12676a5 | 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 | } | |
4a2f7ea2 | 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 (signbit (__real__ res)) | |
74 | __real__ res = 0.0Q; | |
75 | } | |
b12676a5 | 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 | ||
4a2f7ea2 | 85 | if (signbitq (x)) |
b12676a5 | 86 | y = -y; |
87 | ||
88 | __real__ y += __real__ x; | |
89 | __imag__ y += __imag__ x; | |
90 | ||
91 | res = clogq (y); | |
b12676a5 | 92 | } |
93 | ||
94 | return res; | |
95 | } |