forked from KolibriOS/kolibrios
117 lines
2.5 KiB
C
117 lines
2.5 KiB
C
|
|
/* @(#)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) */
|