wcslib (8.2.2)
1 /*============================================================================
2 WCSLIB 8.2 - an implementation of the FITS WCS standard.
3 Copyright (C) 1995-2023, Mark Calabretta
4
5 This file is part of WCSLIB.
6
7 WCSLIB is free software: you can redistribute it and/or modify it under the
8 terms of the GNU Lesser General Public License as published by the Free
9 Software Foundation, either version 3 of the License, or (at your option)
10 any later version.
11
12 WCSLIB is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
14 FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
15 more details.
16
17 You should have received a copy of the GNU Lesser General Public License
18 along with WCSLIB. If not, see http://www.gnu.org/licenses.
19
20 Author: Mark Calabretta, Australia Telescope National Facility, CSIRO.
21 http://www.atnf.csiro.au/people/Mark.Calabretta
22 $Id: wcstrig.h,v 8.2.1.1 2023/11/16 10:05:57 mcalabre Exp mcalabre $
23 *=============================================================================
24 *
25 * WCSLIB 8.2 - C routines that implement the FITS World Coordinate System
26 * (WCS) standard. Refer to the README file provided with WCSLIB for an
27 * overview of the library.
28 *
29 *
30 * Summary of the wcstrig routines
31 * -------------------------------
32 * When dealing with celestial coordinate systems and spherical projections
33 * (some moreso than others) it is often desirable to use an angular measure
34 * that provides an exact representation of the latitude of the north or south
35 * pole. The WCSLIB routines use the following trigonometric functions that
36 * take or return angles in degrees:
37 *
38 * - cosd()
39 * - sind()
40 * - tand()
41 * - acosd()
42 * - asind()
43 * - atand()
44 * - atan2d()
45 * - sincosd()
46 *
47 * These "trigd" routines are expected to handle angles that are a multiple of
48 * 90 degrees returning an exact result. Some C implementations provide these
49 * as part of a system library and in such cases it may (or may not!) be
50 * preferable to use them. WCSLIB provides wrappers on the standard trig
51 * functions based on radian measure, adding tests for multiples of 90 degrees.
52 *
53 * However, wcstrig.h also provides the choice of using preprocessor macro
54 * implementations of the trigd functions that don't test for multiples of
55 * 90 degrees (compile with -DWCSTRIG_MACRO). These are typically 20% faster
56 * but may lead to problems near the poles.
57 *
58 *
59 * cosd() - Cosine of an angle in degrees
60 * --------------------------------------
61 * cosd() returns the cosine of an angle given in degrees.
62 *
63 * Given:
64 * angle double [deg].
65 *
66 * Function return value:
67 * double Cosine of the angle.
68 *
69 *
70 * sind() - Sine of an angle in degrees
71 * ------------------------------------
72 * sind() returns the sine of an angle given in degrees.
73 *
74 * Given:
75 * angle double [deg].
76 *
77 * Function return value:
78 * double Sine of the angle.
79 *
80 *
81 * sincosd() - Sine and cosine of an angle in degrees
82 * --------------------------------------------------
83 * sincosd() returns the sine and cosine of an angle given in degrees.
84 *
85 * Given:
86 * angle double [deg].
87 *
88 * Returned:
89 * sin *double Sine of the angle.
90 *
91 * cos *double Cosine of the angle.
92 *
93 * Function return value:
94 * void
95 *
96 *
97 * tand() - Tangent of an angle in degrees
98 * ---------------------------------------
99 * tand() returns the tangent of an angle given in degrees.
100 *
101 * Given:
102 * angle double [deg].
103 *
104 * Function return value:
105 * double Tangent of the angle.
106 *
107 *
108 * acosd() - Inverse cosine, returning angle in degrees
109 * ----------------------------------------------------
110 * acosd() returns the inverse cosine in degrees.
111 *
112 * Given:
113 * x double in the range [-1,1].
114 *
115 * Function return value:
116 * double Inverse cosine of x [deg].
117 *
118 *
119 * asind() - Inverse sine, returning angle in degrees
120 * --------------------------------------------------
121 * asind() returns the inverse sine in degrees.
122 *
123 * Given:
124 * y double in the range [-1,1].
125 *
126 * Function return value:
127 * double Inverse sine of y [deg].
128 *
129 *
130 * atand() - Inverse tangent, returning angle in degrees
131 * -----------------------------------------------------
132 * atand() returns the inverse tangent in degrees.
133 *
134 * Given:
135 * s double
136 *
137 * Function return value:
138 * double Inverse tangent of s [deg].
139 *
140 *
141 * atan2d() - Polar angle of (x,y), in degrees
142 * -------------------------------------------
143 * atan2d() returns the polar angle, beta, in degrees, of polar coordinates
144 * (rho,beta) corresponding to Cartesian coordinates (x,y). It is equivalent
145 * to the arg(x,y) function of WCS Paper II, though with transposed arguments.
146 *
147 * Given:
148 * y double Cartesian y-coordinate.
149 *
150 * x double Cartesian x-coordinate.
151 *
152 * Function return value:
153 * double Polar angle of (x,y) [deg].
154 *
155 *===========================================================================*/
156
157 #ifndef WCSLIB_WCSTRIG
158 #define WCSLIB_WCSTRIG
159
160 #include <math.h>
161
162 #include "wcsconfig.h"
163
164 #ifdef HAVE_SINCOS
165 void sincos(double angle, double *sin, double *cos);
166 #endif
167
168 #ifdef __cplusplus
169 extern "C" {
170 #endif
171
172
173 #ifdef WCSTRIG_MACRO
174
175 // Macro implementation of the trigd functions.
176 #include "wcsmath.h"
177
178 #define cosd(X) cos((X)*D2R)
179 #define sind(X) sin((X)*D2R)
180 #define tand(X) tan((X)*D2R)
181 #define acosd(X) acos(X)*R2D
182 #define asind(X) asin(X)*R2D
183 #define atand(X) atan(X)*R2D
184 #define atan2d(Y,X) atan2(Y,X)*R2D
185 #ifdef HAVE_SINCOS
186 #define sincosd(X,S,C) sincos((X)*D2R,(S),(C))
187 #else
188 #define sincosd(X,S,C) *(S) = sin((X)*D2R); *(C) = cos((X)*D2R);
189 #endif
190
191 #else
192
193 // Use WCSLIB wrappers or native trigd functions.
194
195 double cosd(double angle);
196 double sind(double angle);
197 void sincosd(double angle, double *sin, double *cos);
198 double tand(double angle);
199 double acosd(double x);
200 double asind(double y);
201 double atand(double s);
202 double atan2d(double y, double x);
203
204 // Domain tolerance for asin() and acos() functions.
205 #define WCSTRIG_TOL 1e-10
206
207 #endif // WCSTRIG_MACRO
208
209
210 #ifdef __cplusplus
211 }
212 #endif
213
214 #endif // WCSLIB_WCSTRIG
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