0,0 → 1,75 |
/* Copyright (C) 1994 DJ Delorie, see COPYING.DJ for details */ |
/* @(#)e_atanh.c 5.1 93/09/24 */ |
/* |
* ==================================================== |
* 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[] = "$Id: e_atanh.c,v 1.6 1994/08/18 23:05:12 jtc Exp $"; |
#endif |
|
/* __ieee754_atanh(x) |
* Method : |
* 1.Reduced x to positive by atanh(-x) = -atanh(x) |
* 2.For x>=0.5 |
* 1 2x x |
* atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------) |
* 2 1 - x 1 - x |
* |
* For x<0.5 |
* atanh(x) = 0.5*log1p(2x+2x*x/(1-x)) |
* |
* Special cases: |
* atanh(x) is NaN if |x| > 1 with signal; |
* atanh(NaN) is that NaN with no signal; |
* atanh(+-1) is +-INF with signal. |
* |
*/ |
|
#include "math.h" |
#include "math_private.h" |
|
#ifdef __STDC__ |
static const double one = 1.0, huge = 1e300; |
#else |
static double one = 1.0, huge = 1e300; |
#endif |
|
#ifdef __STDC__ |
static const double zero = 0.0; |
#else |
static double zero = 0.0; |
#endif |
|
#ifdef __STDC__ |
double __ieee754_atanh(double x) |
#else |
double __ieee754_atanh(x) |
double x; |
#endif |
{ |
double t; |
int32_t hx,ix; |
u_int32_t lx; |
EXTRACT_WORDS(hx,lx,x); |
ix = hx&0x7fffffff; |
if ((ix|((lx|(-lx))>>31))>0x3ff00000) /* |x|>1 */ |
return (x-x)/(x-x); |
if(ix==0x3ff00000) |
return x/zero; |
if(ix<0x3e300000&&(huge+x)>zero) return x; /* x<2**-28 */ |
SET_HIGH_WORD(x,ix); |
if(ix<0x3fe00000) { /* x < 0.5 */ |
t = x+x; |
t = 0.5*log1p(t+t*x/(one-x)); |
} else |
t = 0.5*log1p((x+x)/(one-x)); |
if(hx>=0) return t; else return -t; |
} |