/****************************************************************************/
/*	Copyright (c) 2009, Bendor Research Pty. Ltd. All rights reserved.		*/
/*	This software is released under the GNU General Public License, version	*/
/*	3, with the exemptions that 1) the header files installed by this 	 	*/
/*	package can be included in closed-source code and 2) the libraries		*/
/*	built by this package can be statically linked into a closed-source 	*/
/*	binary. See the file LICENSE for the details.							*/
/*	This software is provided "AS IS", without any warranty or guarantee.	*/
/*	By using this software you acknowledge that neither Bendor Research nor	*/
/*	any of its personnel or affiliates can be held liable for any damages,	*/
/*	including, but not limited to, loss of business, loss of money, loss of */
/*	life, loss of reputation, arising out of this software being faulty or	*/
/*	not performing as advertised, even if Bendor Research was aware of such	*/
/*	faults in the software. You use this software at your own risk, any and */
/*	all liabilities that arise out of your using this software are strictly	*/
/*	yours.																	*/
/****************************************************************************/

#include <math.h>

/****************************************************************************/
/*					Public API functions									*/
/****************************************************************************/

/** @addtogroup func */
/** @{ */

/**
*	Inverse hyperbolic tangent function.
*
*	@param	x		The function argument
*
*	@retval	NaN			The argument was NaN or not in [-1,+1].
*	@retval	+INF		The argument was +1
*	@retval -INF		The argument was -1
*	@retval	atanh(x)	Otherwise
*/

double	atanh( double x )
{
	// Sanity check, range check and special values

	if ( isnan( x ) || x < -1.0 || x > +1.0 ) return( nan( 0 ) );
	if ( x == -1.0 ) return( -infinity() );
	if ( x == +1.0 ) return( +infinity() );
	if ( x ==  0.0 ) return( 0.0 );
	return( ldexp( log( ( 1 + x ) / ( 1 - x ) ), -1 ) );
}

/** @} */

