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//===========================================================================

//

//      e_atanh.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 Red Hat, Inc.

//

// eCos is free software; you can redistribute it and/or modify it under

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// or inline functions from this file, or you compile this file and link it

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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

/* @(#)e_atanh.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_atanh(x)

 * Method :

 *    1.Reduced x to positive by atanh(-x) = -atanh(x)

 *    2.For x>=0.5

 *                  1              2x                          x

 *      atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)

 *                  2             1 - x                      1 - x

 *

 *      For x<0.5

 *      atanh(x) = 0.5*log1p(2x+2x*x/(1-x))

 *

 * Special cases:

 *      atanh(x) is NaN if |x| > 1 with signal;

 *      atanh(NaN) is that NaN with no signal;

 *      atanh(+-1) is +-INF with signal.

 *

 */

#include "mathincl/fdlibm.h"

static const double one = 1.0, huge = 1e300;

static double zero = 0.0;

        double __ieee754_atanh(double x)

{

        double t;

        int hx,ix;

        unsigned lx;

        hx = CYG_LIBM_HI(x);            /* high word */

        lx = CYG_LIBM_LO(x);            /* low word */

        ix = hx&0x7fffffff;

        if ((ix|((lx|(-lx))>>31))>0x3ff00000) /* |x|>1 */

            return (x-x)/(x-x);

        if(ix==0x3ff00000)

            return x/zero;

        if(ix<0x3e300000&&(huge+x)>zero) return x;      /* x<2**-28 */

        CYG_LIBM_HI(x) = ix;            /* x <- |x| */

        if(ix<0x3fe00000) {             /* x < 0.5 */

            t = x+x;

            t = 0.5*log1p(t+t*x/(one-x));

        } else

            t = 0.5*log1p((x+x)/(one-x));

        if(hx>=0) return t; else return -t;

}

#endif // ifdef CYGPKG_LIBM     

// EOF e_atanh.c