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/* @(#)w_log.c 5.1 93/09/24 */

/*

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

 * 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.

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

 */

/*

FUNCTION

       <<log>>, <<logf>>---natural logarithms

INDEX

    log

INDEX

    logf

ANSI_SYNOPSIS

       #include <math.h>

       double log(double <[x]>);

       float logf(float <[x]>);

TRAD_SYNOPSIS

       #include <math.h>

       double log(<[x]>);

       double <[x]>;

       float logf(<[x]>);

       float <[x]>;

DESCRIPTION

Return the natural logarithm of <[x]>, that is, its logarithm base e

(where e is the base of the natural system of logarithms, 2.71828@dots{}).

<<log>> and <<logf>> are identical save for the return and argument types.

You can use the (non-ANSI) function <<matherr>> to specify error

handling for these functions.

RETURNS

Normally, returns the calculated value.  When <[x]> is zero, the

returned value is <<-HUGE_VAL>> and <<errno>> is set to <<ERANGE>>.

When <[x]> is negative, the returned value is NaN (not a number) and

<<errno>> is set to <<EDOM>>.  You can control the error behavior via

<<matherr>>.

PORTABILITY

<<log>> is ANSI. <<logf>> is an extension.

*/

/*

 * wrapper log(x)

 */

#include "fdlibm.h"

#include <errno.h>

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__

        double log(double x)            /* wrapper log */

#else

        double log(x)                   /* wrapper log */

        double x;

#endif

{

#ifdef _IEEE_LIBM

        return __ieee754_log(x);

#else

        double z;

        struct exception exc;

        z = __ieee754_log(x);

        if(_LIB_VERSION == _IEEE_ || isnan(x) || x > 0.0) return z;

#ifndef HUGE_VAL 

#define HUGE_VAL inf

        double inf = 0.0;

        SET_HIGH_WORD(inf,0x7ff00000);  /* set inf to infinite */

#endif

        exc.name = "log";

        exc.err = 0;

        exc.arg1 = x;

        exc.arg2 = x;

        if (_LIB_VERSION == _SVID_)

           exc.retval = -HUGE;

        else

           exc.retval = -HUGE_VAL;

        if(x==0.0) {

            /* log(0) */

            exc.type = SING;

            if (_LIB_VERSION == _POSIX_)

               errno = ERANGE;

            else if (!matherr(&exc)) {

               errno = ERANGE;

            }

        } else {

            /* log(x<0) */

            exc.type = DOMAIN;

            if (_LIB_VERSION == _POSIX_)

               errno = EDOM;

            else if (!matherr(&exc)) {

               errno = EDOM;

            }

            exc.retval = nan("");

        }

        if (exc.err != 0)

           errno = exc.err;

        return exc.retval;

#endif

}

#endif /* defined(_DOUBLE_IS_32BITS) */