1 | /* s_atanhl.c -- long double version of s_atan.c. |
2 | * Conversion to long double by Ulrich Drepper, |
3 | * Cygnus Support, drepper@cygnus.com. |
4 | */ |
5 | |
6 | /* |
7 | * ==================================================== |
8 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
9 | * |
10 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
11 | * Permission to use, copy, modify, and distribute this |
12 | * software is freely granted, provided that this notice |
13 | * is preserved. |
14 | * ==================================================== |
15 | */ |
16 | |
17 | /* __ieee754_atanhl(x) |
18 | * Method : |
19 | * 1.Reduced x to positive by atanh(-x) = -atanh(x) |
20 | * 2.For x>=0.5 |
21 | * 1 2x x |
22 | * atanhl(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------) |
23 | * 2 1 - x 1 - x |
24 | * |
25 | * For x<0.5 |
26 | * atanhl(x) = 0.5*log1pl(2x+2x*x/(1-x)) |
27 | * |
28 | * Special cases: |
29 | * atanhl(x) is NaN if |x| > 1 with signal; |
30 | * atanhl(NaN) is that NaN with no signal; |
31 | * atanhl(+-1) is +-INF with signal. |
32 | * |
33 | */ |
34 | |
35 | #include <float.h> |
36 | #include <math.h> |
37 | #include <math_private.h> |
38 | |
39 | static const long double one = 1.0, huge = 1e4900L; |
40 | |
41 | static const long double zero = 0.0; |
42 | |
43 | long double |
44 | __ieee754_atanhl(long double x) |
45 | { |
46 | long double t; |
47 | int32_t ix; |
48 | uint32_t se,i0,i1; |
49 | GET_LDOUBLE_WORDS(se,i0,i1,x); |
50 | ix = se&0x7fff; |
51 | if ((ix+((((i0&0x7fffffff)|i1)|(-((i0&0x7fffffff)|i1)))>>31))>0x3fff) |
52 | /* |x|>1 */ |
53 | return (x-x)/(x-x); |
54 | if(ix==0x3fff) |
55 | return x/zero; |
56 | if(ix<0x3fdf) { |
57 | math_force_eval(huge+x); |
58 | math_check_force_underflow (x); |
59 | return x; /* x<2**-32 */ |
60 | } |
61 | SET_LDOUBLE_EXP(x,ix); |
62 | if(ix<0x3ffe) { /* x < 0.5 */ |
63 | t = x+x; |
64 | t = 0.5*__log1pl(t+t*x/(one-x)); |
65 | } else |
66 | t = 0.5*__log1pl((x+x)/(one-x)); |
67 | if(se<=0x7fff) return t; else return -t; |
68 | } |
69 | strong_alias (__ieee754_atanhl, __atanhl_finite) |
70 | |