/****************************************************************************/
/*	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 */
/** @{ */

/**
*	Hyperbolic tangent function.
*
*	@param	x		The function argument
*
*	@retval	NaN			The argument was NaN
*	@retval	+1			The argument was +INF
*	@retval -1			The argument was -INF
*	@retval	tanh(x)		Otherwise
*/

float	tanhf( float x )
{
	// Sanity check, range check and special values

	if ( isnan( x ) ) return( x );
	if ( x > +8.5 ) return( +1.0f );
	if ( x < -8.5 ) return( -1.0f );
	if ( x == 0 ) return( 0.0 );

	// We utilise the following identity:
	//
	//			 e^x - e^-x		e^2x - 1
	// tanh(x) = ----------  =  --------
	//			 e^x + e^-x		e^2x + 1

	x = expf( ldexpf( x, 1 ) );
	return( ( x - 1.0f ) / ( x + 1.0f ) );
}

/** @} */

