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//===========================================================================
//
//      s_asinh.c
//
//      Part of the standard mathematical function library
//
//===========================================================================
// ####ECOSGPLCOPYRIGHTBEGIN####                                            
// -------------------------------------------                              
// This file is part of eCos, the Embedded Configurable Operating System.   
// Copyright (C) 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
//
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// for more details.                                                        
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//
// As a special exception, if other files instantiate templates or use      
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// General Public License v2.                                               
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// on this file might be covered by the GNU General Public License.         
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// ####ECOSGPLCOPYRIGHTEND####                                              
//===========================================================================
//#####DESCRIPTIONBEGIN####
//
// Author(s):   jlarmour
// Contributors:  jlarmour
// Date:        1998-02-13
// Purpose:     
// Description: 
// Usage:       
//
//####DESCRIPTIONEND####
//
//===========================================================================
 
// CONFIGURATION
 
#include <pkgconf/libm.h>   // Configuration header
 
// Include the Math library?
#ifdef CYGPKG_LIBM     
 
// Derived from code with the following copyright
 
 
/* @(#)s_asinh.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.
 * ====================================================
 */
 
/* asinh(x)
 * Method :
 *      Based on 
 *              asinh(x) = sign(x) * log [ |x| + sqrt(x*x+1) ]
 *      we have
 *      asinh(x) := x  if  1+x*x=1,
 *               := sign(x)*(log(x)+ln2)) for large |x|, else
 *               := sign(x)*log(2|x|+1/(|x|+sqrt(x*x+1))) if|x|>2, else
 *               := sign(x)*log1p(|x| + x^2/(1 + sqrt(1+x^2)))  
 */
 
#include "mathincl/fdlibm.h"
 
static const double 
one =  1.00000000000000000000e+00, /* 0x3FF00000, 0x00000000 */
ln2 =  6.93147180559945286227e-01, /* 0x3FE62E42, 0xFEFA39EF */
huge=  1.00000000000000000000e+300; 
 
        double asinh(double x)
{       
        double t,w;
        int hx,ix;
        hx = CYG_LIBM_HI(x);
        ix = hx&0x7fffffff;
        if(ix>=0x7ff00000) return x+x;  /* x is inf or NaN */
        if(ix< 0x3e300000) {    /* |x|<2**-28 */
            if(huge+x>one) return x;    /* return x inexact except 0 */
        } 
        if(ix>0x41b00000) {     /* |x| > 2**28 */
            w = __ieee754_log(fabs(x))+ln2;
        } else if (ix>0x40000000) {     /* 2**28 > |x| > 2.0 */
            t = fabs(x);
            w = __ieee754_log(2.0*t+one/(sqrt(x*x+one)+t));
        } else {                /* 2.0 > |x| > 2**-28 */
            t = x*x;
            w =log1p(fabs(x)+t/(one+sqrt(one+t)));
        }
        if(hx>0) return w; else return -w;
}
 
#endif // ifdef CYGPKG_LIBM     
 
// EOF s_asinh.c