blob: dd681c847c3d9dbac554ab5a917d38ddd307baa2 (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
|
/* s_atanhl.c -- long double version of s_atan.c.
* Conversion to long double by Ulrich Drepper,
* Cygnus Support, drepper@cygnus.com.
*/
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
#if defined(LIBM_SCCS) && !defined(lint)
static char rcsid[] = "$NetBSD: $";
#endif
/* __ieee754_atanhl(x)
* Method :
* 1.Reduced x to positive by atanh(-x) = -atanh(x)
* 2.For x>=0.5
* 1 2x x
* atanhl(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
* 2 1 - x 1 - x
*
* For x<0.5
* atanhl(x) = 0.5*log1pl(2x+2x*x/(1-x))
*
* Special cases:
* atanhl(x) is NaN if |x| > 1 with signal;
* atanhl(NaN) is that NaN with no signal;
* atanhl(+-1) is +-INF with signal.
*
*/
#include "math.h"
#include "math_private.h"
#ifdef __STDC__
static const long double one = 1.0L, huge = 1e4900L;
#else
static long double one = 1.0L, huge = 1e4900L;
#endif
#ifdef __STDC__
static const long double zero = 0.0L;
#else
static double long zero = 0.0L;
#endif
#ifdef __STDC__
long double __ieee754_atanhl(long double x)
#else
long double __ieee754_atanhl(x)
long double x;
#endif
{
long double t;
u_int32_t jx, ix;
ieee854_long_double_shape_type u;
u.value = x;
jx = u.parts32.w0;
ix = jx & 0x7fffffff;
u.parts32.w0 = ix;
if (ix >= 0x3fff0000) /* |x| >= 1.0 or infinity or NaN */
{
if (u.value == one)
return x/zero;
else
return (x-x)/(x-x);
}
if(ix<0x3fc60000 && (huge+x)>zero) return x; /* x < 2^-57 */
if(ix<0x3ffe0000) { /* x < 0.5 */
t = u.value+u.value;
t = 0.5*__log1pl(t+t*u.value/(one-u.value));
} else
t = 0.5*__log1pl((u.value+u.value)/(one-u.value));
if(jx & 0x80000000) return -t; else return t;
}
|
