3
* Relative error approximations for function arguments near
7
* expm1(x) = exp(x) - 1
8
* cosm1(x) = cos(x) - 1
14
extern double INFINITY;
17
int isnan(), isfinite();
19
/* log1p(x) = log(1 + x) */
21
/* Coefficients for log(1+x) = x - x**2/2 + x**3 P(x)/Q(x)
22
* 1/sqrt(2) <= x < sqrt(2)
23
* Theoretical peak relative error = 2.32e-20
25
static double LP[] = {
26
4.5270000862445199635215E-5,
27
4.9854102823193375972212E-1,
28
6.5787325942061044846969E0,
29
2.9911919328553073277375E1,
30
6.0949667980987787057556E1,
31
5.7112963590585538103336E1,
32
2.0039553499201281259648E1,
34
static double LQ[] = {
35
/* 1.0000000000000000000000E0,*/
36
1.5062909083469192043167E1,
37
8.3047565967967209469434E1,
38
2.2176239823732856465394E2,
39
3.0909872225312059774938E2,
40
2.1642788614495947685003E2,
41
6.0118660497603843919306E1,
44
#define SQRTH 0.70710678118654752440
45
#define SQRT2 1.41421356237309504880
47
double log(), polevl(), p1evl(), exp(), cos();
50
double log1p(double x)
55
if( (z < SQRTH) || (z > SQRT2) )
58
z = -0.5 * z + x * ( z * polevl( x, LP, 6 ) / p1evl( x, LQ, 6 ) );
64
/* expm1(x) = exp(x) - 1 */
66
/* e^x = 1 + 2x P(x^2)/( Q(x^2) - P(x^2) )
70
static double EP[3] = {
71
1.2617719307481059087798E-4,
72
3.0299440770744196129956E-2,
73
9.9999999999999999991025E-1,
75
static double EQ[4] = {
76
3.0019850513866445504159E-6,
77
2.5244834034968410419224E-3,
78
2.2726554820815502876593E-1,
79
2.0000000000000000000897E0,
82
double expm1(double x)
96
if( (x < -0.5) || (x > 0.5) )
97
return( exp(x) - 1.0 );
99
r = x * polevl( xx, EP, 2 );
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r = r/( polevl( xx, EQ, 3 ) - r );
106
/* cosm1(x) = cos(x) - 1 */
108
static double coscof[7] = {
109
4.7377507964246204691685E-14,
110
-1.1470284843425359765671E-11,
111
2.0876754287081521758361E-9,
112
-2.7557319214999787979814E-7,
113
2.4801587301570552304991E-5,
114
-1.3888888888888872993737E-3,
115
4.1666666666666666609054E-2,
120
double cosm1(double x)
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if( (x < -PIO4) || (x > PIO4) )
125
return( cos(x) - 1.0 );
127
xx = -0.5*xx + xx * xx * polevl( xx, coscof, 6 );