1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
|
/* @(#)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
SYNOPSIS
#include <math.h>
double exp(double <[x]>);
float expf(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).
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"
#if __OBSOLETE_MATH
#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;
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
errno = ERANGE;
return HUGE_VAL;
} else if(x<u_threshold) {
/* exp(finite) underflow */
errno = ERANGE;
return 0.0;
}
}
return z;
#endif
}
#endif /* defined(_DOUBLE_IS_32BITS) */
#endif /* __OBSOLETE_MATH */
|
