File: tandg.c

package info (click to toggle)
python-scipy 0.18.1-2
  • links: PTS, VCS
  • area: main
  • in suites: stretch
  • size: 75,464 kB
  • ctags: 79,406
  • sloc: python: 143,495; cpp: 89,357; fortran: 81,650; ansic: 79,778; makefile: 364; sh: 265
file content (141 lines) | stat: -rw-r--r-- 2,554 bytes parent folder | download | duplicates (2)
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
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
/*                                                     tandg.c
 *
 *     Circular tangent of argument in degrees
 *
 *
 *
 * SYNOPSIS:
 *
 * double x, y, tandg();
 *
 * y = tandg( x );
 *
 *
 *
 * DESCRIPTION:
 *
 * Returns the circular tangent of the argument x in degrees.
 *
 * Range reduction is modulo pi/4.  A rational function
 *       x + x**3 P(x**2)/Q(x**2)
 * is employed in the basic interval [0, pi/4].
 *
 *
 *
 * ACCURACY:
 *
 *                      Relative error:
 * arithmetic   domain     # trials      peak         rms
 *    IEEE     0,10         30000      3.2e-16      8.4e-17
 *
 * ERROR MESSAGES:
 *
 *   message         condition          value returned
 * tandg total loss   x > 1.0e14 (IEEE)     0.0
 * tandg singularity  x = 180 k  +  90     NPY_INFINITY
 */
/*							cotdg.c
 *
 *	Circular cotangent of argument in degrees
 *
 *
 *
 * SYNOPSIS:
 *
 * double x, y, cotdg();
 *
 * y = cotdg( x );
 *
 *
 *
 * DESCRIPTION:
 *
 * Returns the circular cotangent of the argument x in degrees.
 *
 * Range reduction is modulo pi/4.  A rational function
 *       x + x**3 P(x**2)/Q(x**2)
 * is employed in the basic interval [0, pi/4].
 *
 *
 * ERROR MESSAGES:
 *
 *   message         condition          value returned
 * cotdg total loss   x > 1.0e14 (IEEE)     0.0
 * cotdg singularity  x = 180 k            NPY_INFINITY
 */

/*
 * Cephes Math Library Release 2.0:  April, 1987
 * Copyright 1984, 1987 by Stephen L. Moshier
 * Direct inquiries to 30 Frost Street, Cambridge, MA 02140
 */

#include "mconf.h"

static double PI180 = 1.74532925199432957692E-2;
static double lossth = 1.0e14;

static double tancot(double, int);

double tandg(double x)
{
    return (tancot(x, 0));
}


double cotdg(double x)
{
    return (tancot(x, 1));
}


static double tancot(double xx, int cotflg)
{
    double x;
    int sign;

    /* make argument positive but save the sign */
    if (xx < 0) {
	x = -xx;
	sign = -1;
    }
    else {
	x = xx;
	sign = 1;
    }

    if (x > lossth) {
	mtherr("tandg", TLOSS);
	return 0.0;
    }

    /* modulo 180 */
    x = x - 180.0 * floor(x / 180.0);
    if (cotflg) {
	if (x <= 90.0) {
	    x = 90.0 - x;
	}
	else {
	    x = x - 90.0;
	    sign *= -1;
	}
    }
    else {
	if (x > 90.0) {
	    x = 180.0 - x;
	    sign *= -1;
	}
    }
    if (x == 0.0) {
	return 0.0;
    }
    else if (x == 45.0) {
	return sign * 1.0;
    }
    else if (x == 90.0) {
	mtherr((cotflg ? "cotdg" : "tandg"), SING);
	return NPY_INFINITY;
    }
    /* x is now transformed into [0, 90) */
    return sign * tan(x * PI180);
}