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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
SYNOPSIS
#include <math.h>
double log(double <[x]>);
float logf(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"
#if __OBSOLETE_MATH
#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) */
#endif /* __OBSOLETE_MATH */
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