mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-23 13:30:06 +00:00
68 lines
1.8 KiB
C
68 lines
1.8 KiB
C
/* s_atanhl.c -- long double version of s_atan.c.
|
|
* Conversion to long double by Ulrich Drepper,
|
|
* Cygnus Support, drepper@cygnus.com.
|
|
*/
|
|
|
|
/*
|
|
* ====================================================
|
|
* 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_atanhl(x)
|
|
* Method :
|
|
* 1.Reduced x to positive by atanh(-x) = -atanh(x)
|
|
* 2.For x>=0.5
|
|
* 1 2x x
|
|
* atanhl(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
|
|
* 2 1 - x 1 - x
|
|
*
|
|
* For x<0.5
|
|
* atanhl(x) = 0.5*log1pl(2x+2x*x/(1-x))
|
|
*
|
|
* Special cases:
|
|
* atanhl(x) is NaN if |x| > 1 with signal;
|
|
* atanhl(NaN) is that NaN with no signal;
|
|
* atanhl(+-1) is +-INF with signal.
|
|
*
|
|
*/
|
|
|
|
#include "math.h"
|
|
#include "math_private.h"
|
|
|
|
static const long double one = 1.0, huge = 1e4900L;
|
|
|
|
static const long double zero = 0.0;
|
|
|
|
long double
|
|
__ieee754_atanhl(long double x)
|
|
{
|
|
long double t;
|
|
int32_t ix;
|
|
u_int32_t se,i0,i1;
|
|
GET_LDOUBLE_WORDS(se,i0,i1,x);
|
|
ix = se&0x7fff;
|
|
if ((ix+((((i0&0x7fffffff)|i1)|(-((i0&0x7fffffff)|i1)))>>31))>0x3fff)
|
|
/* |x|>1 */
|
|
return (x-x)/(x-x);
|
|
if(ix==0x3fff)
|
|
return x/zero;
|
|
if(ix<0x3fe3) {
|
|
math_force_eval(huge+x);
|
|
return x; /* x<2**-28 */
|
|
}
|
|
SET_LDOUBLE_EXP(x,ix);
|
|
if(ix<0x3ffe) { /* 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(se<=0x7fff) return t; else return -t;
|
|
}
|
|
strong_alias (__ieee754_atanhl, __atanhl_finite)
|