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[glibc/history.git] / math / s_cacosh.c
blobada7ca5af6163a903cc831e3ad56949afda59920
1 /* Return arc hyperbole cosine for double value.
2 Copyright (C) 1997, 2006 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
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.
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.
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. */
21 #include <complex.h>
22 #include <math.h>
25 __complex__ double
26 __cacosh (__complex__ double x)
28 __complex__ double res;
29 int rcls = fpclassify (__real__ x);
30 int icls = fpclassify (__imag__ x);
32 if (rcls <= FP_INFINITE || icls <= FP_INFINITE)
34 if (icls == FP_INFINITE)
36 __real__ res = HUGE_VAL;
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);
46 else if (rcls == FP_INFINITE)
48 __real__ res = HUGE_VAL;
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 ("");
56 else
58 __real__ res = __nan ("");
59 __imag__ res = __nan ("");
62 else if (rcls == FP_ZERO && icls == FP_ZERO)
64 __real__ res = 0.0;
65 __imag__ res = __copysign (M_PI_2, __imag__ x);
67 else
69 __complex__ double y;
71 __real__ y = (__real__ x - __imag__ x) * (__real__ x + __imag__ x) - 1.0;
72 __imag__ y = 2.0 * __real__ x * __imag__ x;
74 y = __csqrt (y);
76 if (__real__ x < 0.0)
77 y = -y;
79 __real__ y += __real__ x;
80 __imag__ y += __imag__ x;
82 res = __clog (y);
84 /* We have to use the positive branch. */
85 if (__real__ res < 0.0)
86 res = -res;
89 return res;
91 weak_alias (__cacosh, cacosh)
92 #ifdef NO_LONG_DOUBLE
93 strong_alias (__cacosh, __cacoshl)
94 weak_alias (__cacosh, cacoshl)
95 #endif