1 /* Return arc hyperbole cosine for float value.
2 Copyright (C) 1997, 2006, 2011 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, see
18 <http://www.gnu.org/licenses/>. */
23 #include <math_private.h>
26 __cacoshf (__complex__
float x
)
28 __complex__
float 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_VALF
;
39 __imag__ res
= __nanf ("");
41 __imag__ res
= __copysignf ((rcls
== FP_INFINITE
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_VALF
;
51 __imag__ res
= __copysignf (signbit (__real__ x
) ? M_PI
: 0.0,
54 __imag__ res
= __nanf ("");
58 __real__ res
= __nanf ("");
59 __imag__ res
= __nanf ("");
62 else if (rcls
== FP_ZERO
&& icls
== FP_ZERO
)
65 __imag__ res
= __copysignf (M_PI_2
, __imag__ x
);
67 /* The factor 16 is just a guess. */
68 else if (16.0 * fabsf (__imag__ x
) < fabsf (__real__ x
))
69 /* Kahan's formula which avoid cancellation through subtraction in
71 res
= 2.0 * __clogf (__csqrtf ((x
+ 1.0) / 2.0)
72 + __csqrtf ((x
- 1.0) / 2.0));
77 __real__ y
= (__real__ x
- __imag__ x
) * (__real__ x
+ __imag__ x
) - 1.0;
78 __imag__ y
= 2.0 * __real__ x
* __imag__ x
;
82 if (signbit (__real__ x
))
85 __real__ y
+= __real__ x
;
86 __imag__ y
+= __imag__ x
;
94 weak_alias (__cacoshf
, cacoshf
)