mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-30 08:40:07 +00:00
65 lines
1.7 KiB
C
65 lines
1.7 KiB
C
/* @(#)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.
|
|
* ====================================================
|
|
*/
|
|
|
|
/* __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>
|
|
|
|
static const long double one = 1.0L, huge = 1e300L;
|
|
|
|
static const long double zero = 0.0L;
|
|
|
|
long double
|
|
__ieee754_atanhl(long double x)
|
|
{
|
|
long double t;
|
|
int64_t hx,ix;
|
|
u_int64_t lx __attribute__ ((unused));
|
|
GET_LDOUBLE_WORDS64(hx,lx,x);
|
|
ix = hx&0x7fffffffffffffffLL;
|
|
if (ix >= 0x3ff0000000000000LL) { /* |x|>=1 */
|
|
if (ix > 0x3ff0000000000000LL)
|
|
return (x-x)/(x-x);
|
|
t = fabsl (x);
|
|
if (t > one)
|
|
return (x-x)/(x-x);
|
|
if (t == one)
|
|
return x/zero;
|
|
}
|
|
if(ix<0x3e20000000000000LL&&(huge+x)>zero) return x; /* x<2**-29 */
|
|
x = fabsl (x);
|
|
if(ix<0x3fe0000000000000LL) { /* x < 0.5 */
|
|
t = x+x;
|
|
t = 0.5*__log1pl(t+t*x/(one-x));
|
|
} else
|
|
t = 0.5*__log1pl((x+x)/(one-x));
|
|
if(hx>=0) return t; else return -t;
|
|
}
|
|
strong_alias (__ieee754_atanhl, __atanhl_finite)
|