/* @(#)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 <float.h>

#include <math.h>

#include <math_private.h>

#include <math-underflow.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;

	double xhi;

	xhi = ldbl_high (x);

	EXTRACT_WORDS64 (hx, xhi);

	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<0x3c70000000000000LL&&(huge+x)>zero)	/* x<2**-56 */

	  {

	    math_check_force_underflow (x);

	    return x;

	  }

	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)