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/* 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 <float.h>
#include <math.h>
#include <math-barriers.h>
#include <math_private.h>
#include <math-underflow.h>
#include <libm-alias-finite.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;
uint32_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<0x3fdf) {
math_force_eval(huge+x);
math_check_force_underflow (x);
return x; /* x<2**-32 */
}
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;
}
libm_alias_finite (__ieee754_atanhl, __atanhl)
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