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/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2011 Nexenta Systems, Inc. All rights reserved.
*/
/*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#pragma weak atanhl = __atanhl
#include "libm.h"
#include "libm_synonyms.h"
#define GENERIC long double
#define ATANH atanhl
/* ATANH(x)
* 1 2x x
* ATANH(x) = --- * LOG(1 + -------) = 0.5 * LOG1P(2 * --------)
* 2 1 - x 1 - x
* Note: to guarantee ATANH(-x) = -ATANH(x), we use
* sign(x) |x|
* ATANH(x) = ------- * LOG1P(2*-------).
* 2 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.
*
*/
#define FABS fabsl
#define LOG1P log1pl
#define COPYSIGN copysignl
extern GENERIC FABS(),LOG1P(),COPYSIGN();
static GENERIC
zero = (GENERIC) 0.0,
half = (GENERIC) 0.5,
one = (GENERIC) 1.0;
GENERIC ATANH(x)
GENERIC x;
{
GENERIC t;
t = FABS(x);
if (t == one) return x/zero;
t = t/(one-t);
return COPYSIGN(half,x)*LOG1P(t+t);
}
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