]>
Commit | Line | Data |
---|---|---|
f964490f RM |
1 | /* @(#)e_atanh.c 5.1 93/09/24 */ |
2 | /* | |
3 | * ==================================================== | |
4 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. | |
5 | * | |
6 | * Developed at SunPro, a Sun Microsystems, Inc. business. | |
7 | * Permission to use, copy, modify, and distribute this | |
8 | * software is freely granted, provided that this notice | |
9 | * is preserved. | |
10 | * ==================================================== | |
11 | */ | |
12 | ||
f964490f RM |
13 | /* __ieee754_atanh(x) |
14 | * Method : | |
15 | * 1.Reduced x to positive by atanh(-x) = -atanh(x) | |
16 | * 2.For x>=0.5 | |
17 | * 1 2x x | |
18 | * atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------) | |
19 | * 2 1 - x 1 - x | |
20 | * | |
0ac5ae23 | 21 | * For x<0.5 |
f964490f RM |
22 | * atanh(x) = 0.5*log1p(2x+2x*x/(1-x)) |
23 | * | |
24 | * Special cases: | |
25 | * atanh(x) is NaN if |x| > 1 with signal; | |
26 | * atanh(NaN) is that NaN with no signal; | |
27 | * atanh(+-1) is +-INF with signal. | |
28 | * | |
29 | */ | |
30 | ||
31 | #include "math.h" | |
32 | #include "math_private.h" | |
33 | ||
f964490f | 34 | static const long double one = 1.0L, huge = 1e300L; |
f964490f | 35 | |
f964490f | 36 | static const long double zero = 0.0L; |
f964490f | 37 | |
0ac5ae23 UD |
38 | long double |
39 | __ieee754_atanhl(long double x) | |
f964490f RM |
40 | { |
41 | long double t; | |
42 | int64_t hx,ix; | |
43 | u_int64_t lx; | |
44 | GET_LDOUBLE_WORDS64(hx,lx,x); | |
45 | ix = hx&0x7fffffffffffffffLL; | |
46 | if (ix >= 0x3ff0000000000000LL) { /* |x|>=1 */ | |
47 | if (ix > 0x3ff0000000000000LL) | |
0ac5ae23 | 48 | return (x-x)/(x-x); |
f964490f RM |
49 | t = fabsl (x); |
50 | if (t > one) | |
51 | return (x-x)/(x-x); | |
52 | if (t == one) | |
53 | return x/zero; | |
54 | } | |
55 | if(ix<0x3e20000000000000LL&&(huge+x)>zero) return x; /* x<2**-29 */ | |
56 | x = fabsl (x); | |
57 | if(ix<0x3fe0000000000000LL) { /* x < 0.5 */ | |
58 | t = x+x; | |
59 | t = 0.5*__log1pl(t+t*x/(one-x)); | |
60 | } else | |
61 | t = 0.5*__log1pl((x+x)/(one-x)); | |
62 | if(hx>=0) return t; else return -t; | |
63 | } | |
0ac5ae23 | 64 | strong_alias (__ieee754_atanhl, __atanhl_finite) |