projects / thirdparty / glibc.git / blame
| Commit | Line | Data |
|---|---|---|
| dd98116c AJ |
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 | ||
| dd98116c AJ |
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 | * | |
| 0ac5ae23 | 25 | * For x<0.5 |
| dd98116c AJ |
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 "math.h" | |
| 36 | #include "math_private.h" | |
| 37 | ||
| dd98116c | 38 | static const long double one = 1.0L, huge = 1e4900L; |
| dd98116c | 39 | |
| dd98116c | 40 | static const long double zero = 0.0L; |
| dd98116c | 41 | |
| 0ac5ae23 UD |
42 | long double |
| 43 | __ieee754_atanhl(long double x) | |
| dd98116c AJ |
44 | { |
| 45 | long double t; | |
| 46 | u_int32_t jx, ix; | |
| 47 | ieee854_long_double_shape_type u; | |
| 48 | ||
| 49 | u.value = x; | |
| 50 | jx = u.parts32.w0; | |
| 51 | ix = jx & 0x7fffffff; | |
| 52 | u.parts32.w0 = ix; | |
| 53 | if (ix >= 0x3fff0000) /* |x| >= 1.0 or infinity or NaN */ | |
| 54 | { | |
| 55 | if (u.value == one) | |
| 56 | return x/zero; | |
| 57 | else | |
| 58 | return (x-x)/(x-x); | |
| 59 | } | |
| 60 | if(ix<0x3fc60000 && (huge+x)>zero) return x; /* x < 2^-57 */ | |
| 61 | ||
| 62 | if(ix<0x3ffe0000) { /* x < 0.5 */ | |
| 63 | t = u.value+u.value; | |
| 64 | t = 0.5*__log1pl(t+t*u.value/(one-u.value)); | |
| 65 | } else | |
| 66 | t = 0.5*__log1pl((u.value+u.value)/(one-u.value)); | |
| 67 | if(jx & 0x80000000) return -t; else return t; | |
| 68 | } | |
| 0ac5ae23 | 69 | strong_alias (__ieee754_atanhl, __atanhl_finite) |