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/* @(#)w_exp.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
<<exp>>, <<expf>>---exponential
INDEX
exp
INDEX
expf
ANSI_SYNOPSIS
#include <math.h>
double exp(double <[x]>);
float expf(float <[x]>);
TRAD_SYNOPSIS
#include <math.h>
double exp(<[x]>);
double <[x]>;
float expf(<[x]>);
float <[x]>;
DESCRIPTION
<<exp>> and <<expf>> calculate the exponential of <[x]>, that is,
@ifnottex
e raised to the power <[x]> (where e
@end ifnottex
@tex
$e^x$ (where $e$
@end tex
is the base of the natural system of logarithms, approximately 2.71828).
You can use the (non-ANSI) function <<matherr>> to specify
error handling for these functions.
RETURNS
On success, <<exp>> and <<expf>> return the calculated value.
If the result underflows, the returned value is <<0>>. If the
result overflows, the returned value is <<HUGE_VAL>>. In
either case, <<errno>> is set to <<ERANGE>>.
PORTABILITY
<<exp>> is ANSI C. <<expf>> is an extension.
*/
/*
* wrapper exp(x)
*/
#include "fdlibm.h"
#include <errno.h>
#ifndef _DOUBLE_IS_32BITS
#ifdef __STDC__
static const double
#else
static double
#endif
o_threshold= 7.09782712893383973096e+02, /* 0x40862E42, 0xFEFA39EF */
u_threshold= -7.45133219101941108420e+02; /* 0xc0874910, 0xD52D3051 */
#ifdef __STDC__
double exp(double x) /* wrapper exp */
#else
double exp(x) /* wrapper exp */
double x;
#endif
{
#ifdef _IEEE_LIBM
return __ieee754_exp(x);
#else
double z;
struct exception exc;
z = __ieee754_exp(x);
if(_LIB_VERSION == _IEEE_) return z;
if(finite(x)) {
if(x>o_threshold) {
/* exp(finite) overflow */
#ifndef HUGE_VAL
#define HUGE_VAL inf
double inf = 0.0;
SET_HIGH_WORD(inf,0x7ff00000); /* set inf to infinite */
#endif
exc.type = OVERFLOW;
exc.name = "exp";
exc.err = 0;
exc.arg1 = exc.arg2 = x;
if (_LIB_VERSION == _SVID_)
exc.retval = HUGE;
else
exc.retval = HUGE_VAL;
if (_LIB_VERSION == _POSIX_)
errno = ERANGE;
else if (!matherr(&exc)) {
errno = ERANGE;
}
if (exc.err != 0)
errno = exc.err;
return exc.retval;
} else if(x<u_threshold) {
/* exp(finite) underflow */
exc.type = UNDERFLOW;
exc.name = "exp";
exc.err = 0;
exc.arg1 = exc.arg2 = x;
exc.retval = 0.0;
if (_LIB_VERSION == _POSIX_)
errno = ERANGE;
else if (!matherr(&exc)) {
errno = ERANGE;
}
if (exc.err != 0)
errno = exc.err;
return exc.retval;
}
}
return z;
#endif
}
#endif /* defined(_DOUBLE_IS_32BITS) */
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