/* @(#)e_sinh.c 1.3 95/01/18 */

/*

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

 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.

 *

 * Developed at SunSoft, a Sun Microsystems, Inc. business.

 * Permission to use, copy, modify, and distribute this

 * software is freely granted, provided that this notice 

 * is preserved.

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

 */

/* __ieee754_sinh(x)

 * Method : 

 * mathematically sinh(x) if defined to be (exp(x)-exp(-x))/2

 *	1. Replace x by |x| (sinh(-x) = -sinh(x)). 

 *	2. 

 *		                                    E + E/(E+1)

 *	    0        <= x <= 22     :  sinh(x) := --------------, E=expm1(x)

 *			       			        2

 *

 *	    22       <= x <= lnovft :  sinh(x) := exp(x)/2 

 *	    lnovft   <= x <= ln2ovft:  sinh(x) := exp(x/2)/2 * exp(x/2)

 *	    ln2ovft  <  x	    :  sinh(x) := x*shuge (overflow)

 *

 * Special cases:

 *	sinh(x) is |x| if x is +INF, -INF, or NaN.

 *	only sinh(0)=0 is exact for finite x.

 */

#include "fdlibm.h"

#ifdef __STDC__

static const double one = 1.0, shuge = 1.0e307;

#else

static double one = 1.0, shuge = 1.0e307;

#endif

#ifdef __STDC__

	double __ieee754_sinh(double x)

#else

	double __ieee754_sinh(x)

	double x;

#endif

{	

	double t,w,h;

	int ix,jx;

	unsigned lx;

    /* High word of |x|. */

	jx = __HI(x);

	ix = jx&0x7fffffff;

    /* x is INF or NaN */

	if(ix>=0x7ff00000) return x+x;	

	h = 0.5;

	if (jx<0) h = -h;

    /* |x| in [0,22], return sign(x)*0.5*(E+E/(E+1))) */

	if (ix < 0x40360000) {		/* |x|<22 */

	    if (ix<0x3e300000) 		/* |x|<2**-28 */

		if(shuge+x>one) return x;/* sinh(tiny) = tiny with inexact */

	    t = expm1(fabs(x));

	    if(ix<0x3ff00000) return h*(2.0*t-t*t/(t+one));

	    return h*(t+t/(t+one));

	}

    /* |x| in [22, log(maxdouble)] return 0.5*exp(|x|) */

	if (ix < 0x40862E42)  return h*__ieee754_exp(fabs(x));

    /* |x| in [log(maxdouble), overflowthresold] */

	lx = *( (((*(unsigned*)&one)>>29)) + (unsigned*)&x);

	if (ix<0x408633CE || (ix==0x408633ce)&&(lx<=(unsigned)0x8fb9f87d)) {

	    w = __ieee754_exp(0.5*fabs(x));

	    t = h*w;

	    return t*w;

	}

    /* |x| > overflowthresold, sinh(x) overflow */

	return x*shuge;

}