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# wcstrig.h

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    00001 /*============================================================================
    00002
    00003   WCSLIB 4.10 - an implementation of the FITS WCS standard.
    00004   Copyright (C) 1995-2012, Mark Calabretta
    00005
    00006   This file is part of WCSLIB.
    00007
    00008   WCSLIB is free software: you can redistribute it and/or modify it under the
    00009   terms of the GNU Lesser General Public License as published by the Free
    00010   Software Foundation, either version 3 of the License, or (at your option)
    00011   any later version.
    00012
    00013   WCSLIB is distributed in the hope that it will be useful, but WITHOUT ANY
    00014   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
    00015   FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for
    00016   more details.
    00017
    00018   You should have received a copy of the GNU Lesser General Public License
    00019   along with WCSLIB.  If not, see <http://www.gnu.org/licenses/>.
    00020
    00021   Correspondence concerning WCSLIB may be directed to:
    00022     Internet email: mcalabre@atnf.csiro.au
    00023     Postal address: Dr. Mark Calabretta
    00024                     Australia Telescope National Facility, CSIRO
    00025                     PO Box 76
    00026                     Epping NSW 1710
    00027                     AUSTRALIA
    00028
    00029   Author: Mark Calabretta, Australia Telescope National Facility
    00030   http://www.atnf.csiro.au/~mcalabre/index.html
    00031   $Id: wcstrig.h,v 4.10 2012/02/05 23:41:44 cal103 Exp $
    00032 *=============================================================================
    00033 *
    00034 * Summary of the wcstrig routines
    00035 * -------------------------------
    00036 * When dealing with celestial coordinate systems and spherical projections
    00037 * (some moreso than others) it is often desirable to use an angular measure
    00038 * that provides an exact representation of the latitude of the north or south
    00039 * pole.  The WCSLIB routines use the following trigonometric functions that
    00040 * take or return angles in degrees:
    00041 *
    00042 *   - cosd()
    00043 *   - sind()
    00044 *   - tand()
    00045 *   - acosd()
    00046 *   - asind()
    00047 *   - atand()
    00048 *   - atan2d()
    00049 *   - sincosd()
    00050 *
    00051 * These "trigd" routines are expected to handle angles that are a multiple of
    00052 * 90 degrees returning an exact result.  Some C implementations provide these
    00053 * as part of a system library and in such cases it may (or may not!) be
    00054 * preferable to use them.  WCSLIB provides wrappers on the standard trig
    00055 * functions based on radian measure, adding tests for multiples of 90 degrees.
    00056 *
    00057 * However, wcstrig.h also provides the choice of using preprocessor macro
    00058 * implementations of the trigd functions that don't test for multiples of
    00059 * 90 degrees (compile with -DWCSTRIG_MACRO).  These are typically 20% faster
    00060 * but may lead to problems near the poles.
    00061 *
    00062 *
    00063 * cosd() - Cosine of an angle in degrees
    00064 * --------------------------------------
    00065 * cosd() returns the cosine of an angle given in degrees.
    00066 *
    00067 * Given:
    00068 *   angle     double    [deg].
    00069 *
    00070 * Function return value:
    00071 *             double    Cosine of the angle.
    00072 *
    00073 *
    00074 * sind() - Sine of an angle in degrees
    00075 * ------------------------------------
    00076 * sind() returns the sine of an angle given in degrees.
    00077 *
    00078 * Given:
    00079 *   angle     double    [deg].
    00080 *
    00081 * Function return value:
    00082 *             double    Sine of the angle.
    00083 *
    00084 *
    00085 * sincosd() - Sine and cosine of an angle in degrees
    00086 * --------------------------------------------------
    00087 * sincosd() returns the sine and cosine of an angle given in degrees.
    00088 *
    00089 * Given:
    00090 *   angle     double    [deg].
    00091 *
    00092 * Returned:
    00093 *   sin       *double   Sine of the angle.
    00094 *
    00095 *   cos       *double   Cosine of the angle.
    00096 *
    00097 * Function return value:
    00098 *             void
    00099 *
    00100 *
    00101 * tand() - Tangent of an angle in degrees
    00102 * ---------------------------------------
    00103 * tand() returns the tangent of an angle given in degrees.
    00104 *
    00105 * Given:
    00106 *   angle     double    [deg].
    00107 *
    00108 * Function return value:
    00109 *             double    Tangent of the angle.
    00110 *
    00111 *
    00112 * acosd() - Inverse cosine, returning angle in degrees
    00113 * ----------------------------------------------------
    00114 * acosd() returns the inverse cosine in degrees.
    00115 *
    00116 * Given:
    00117 *   x         double    in the range [-1,1].
    00118 *
    00119 * Function return value:
    00120 *             double    Inverse cosine of x [deg].
    00121 *
    00122 *
    00123 * asind() - Inverse sine, returning angle in degrees
    00124 * --------------------------------------------------
    00125 * asind() returns the inverse sine in degrees.
    00126 *
    00127 * Given:
    00128 *   y         double    in the range [-1,1].
    00129 *
    00130 * Function return value:
    00131 *             double    Inverse sine of y [deg].
    00132 *
    00133 *
    00134 * atand() - Inverse tangent, returning angle in degrees
    00135 * -----------------------------------------------------
    00136 * atand() returns the inverse tangent in degrees.
    00137 *
    00138 * Given:
    00139 *   s         double
    00140 *
    00141 * Function return value:
    00142 *             double    Inverse tangent of s [deg].
    00143 *
    00144 *
    00145 * atan2d() - Polar angle of (x,y), in degrees
    00146 * -------------------------------------------
    00147 * atan2d() returns the polar angle, beta, in degrees, of polar coordinates
    00148 * (rho,beta) corresponding Cartesian coordinates (x,y).  It is equivalent to
    00149 * the arg(x,y) function of WCS Paper II, though with transposed arguments.
    00150 *
    00151 * Given:
    00152 *   y         double    Cartesian y-coordinate.
    00153 *
    00154 *   x         double    Cartesian x-coordinate.
    00155 *
    00156 * Function return value:
    00157 *             double    Polar angle of (x,y) [deg].
    00158 *
    00159 *===========================================================================*/
    00160
    00161 #ifndef WCSLIB_WCSTRIG
    00162 #define WCSLIB_WCSTRIG
    00163
    00164 #include <math.h>
    00165
    00166 #include "wcsconfig.h"
    00167
    00168 #ifdef HAVE_SINCOS
    00169   void sincos(double angle, double *sin, double *cos);
    00170 #endif
    00171
    00172 #ifdef __cplusplus
    00173 extern "C" {
    00174 #endif
    00175
    00176
    00177 #ifdef WCSTRIG_MACRO
    00178
    00179 /* Macro implementation of the trigd functions. */
    00180 #include "wcsmath.h"
    00181
    00182 #define cosd(X) cos((X)*D2R)
    00183 #define sind(X) sin((X)*D2R)
    00184 #define tand(X) tan((X)*D2R)
    00185 #define acosd(X) acos(X)*R2D
    00186 #define asind(X) asin(X)*R2D
    00187 #define atand(X) atan(X)*R2D
    00188 #define atan2d(Y,X) atan2(Y,X)*R2D
    00189 #ifdef HAVE_SINCOS
    00190   #define sincosd(X,S,C) sincos((X)*D2R,(S),(C))
    00191 #else
    00192   #define sincosd(X,S,C) *(S) = sin((X)*D2R); *(C) = cos((X)*D2R);
    00193 #endif
    00194
    00195 #else
    00196
    00197 /* Use WCSLIB wrappers or native trigd functions. */
    00198
    00199 double cosd(double angle);
    00200 double sind(double angle);
    00201 void sincosd(double angle, double *sin, double *cos);
    00202 double tand(double angle);
    00203 double acosd(double x);
    00204 double asind(double y);
    00205 double atand(double s);
    00206 double atan2d(double y, double x);
    00207
    00208 /* Domain tolerance for asin() and acos() functions. */
    00209 #define WCSTRIG_TOL 1e-10
    00210
    00211 #endif /* WCSTRIG_MACRO */
    00212
    00213
    00214 #ifdef __cplusplus
    00215 }
    00216 #endif
    00217
    00218 #endif /* WCSLIB_WCSTRIG */