/* s_tanhl.c -- long double version of s_tanh.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.

 * ====================================================

 */

#if defined(LIBM_SCCS) && !defined(lint)

static char rcsid[] = "$NetBSD: $";

#endif

/* tanhl(x)

 * Return the Hyperbolic Tangent of x

 *

 * Method :

 *				        x    -x

 *				       e  - e

 *	0. tanhl(x) is defined to be -----------

 *				        x    -x

 *				       e  + e

 *	1. reduce x to non-negative by tanhl(-x) = -tanhl(x).

 *	2.  0      <= x <= 2**-55 : tanhl(x) := x*(one+x)

 *					         -t

 *	    2**-55 <  x <=  1     : tanhl(x) := -----; t = expm1l(-2x)

 *					        t + 2

 *						      2

 *	    1      <= x <=  23.0  : tanhl(x) := 1-  ----- ; t=expm1l(2x)

 *						    t + 2

 *	    23.0   <  x <= INF    : tanhl(x) := 1.

 *

 * Special cases:

 *	tanhl(NaN) is NaN;

 *	only tanhl(0)=0 is exact for finite argument.

 */

#include <float.h>

#include <math.h>

#include <math_private.h>

#include <math-underflow.h>

#include <libm-alias-ldouble.h>

static const long double one=1.0, two=2.0, tiny = 1.0e-4900L;

long double __tanhl(long double x)

{

	long double t,z;

	int32_t se;

	uint32_t j0,j1,ix;

    /* High word of |x|. */

	GET_LDOUBLE_WORDS(se,j0,j1,x);

	ix = se&0x7fff;

    /* x is INF or NaN */

	if(ix==0x7fff) {

	    /* for NaN it's not important which branch: tanhl(NaN) = NaN */

	    if (se&0x8000) return one/x-one;	/* tanhl(-inf)= -1; */

	    else           return one/x+one;	/* tanhl(+inf)=+1 */

	}

    /* |x| < 23 */

	if (ix < 0x4003 || (ix == 0x4003 && j0 < 0xb8000000u)) {/* |x|<23 */

	    if ((ix|j0|j1) == 0)

		return x;		/* x == +- 0 */

	    if (ix<0x3fc8)		/* |x|<2**-55 */

	      {

		math_check_force_underflow (x);

		return x*(one+tiny);	/* tanh(small) = small */

	      }

	    if (ix>=0x3fff) {	/* |x|>=1  */

		t = __expm1l(two*fabsl(x));

		z = one - two/(t+two);

	    } else {

	        t = __expm1l(-two*fabsl(x));

	        z= -t/(t+two);

	    }

    /* |x| > 23, return +-1 */

	} else {

	    z = one - tiny;		/* raised inexact flag */

	}

	return (se&0x8000)? -z: z;

}

libm_alias_ldouble (__tanh, tanh)