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/**
* Copyright © 2016 Mattias Andrée <maandree@member.fsf.org>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* Approximate apparent size of the Sun in degrees.
*/
#define SOLAR_APPARENT_RADIUS (32.0 / 60.0)
/**
* The Sun's elevation at sunset and sunrise, measured in degrees.
*/
#define SOLAR_ELEVATION_SUNSET_SUNRISE (0.0)
/**
* The Sun's elevation at civil dusk and civil dawn, measured in degrees.
*/
#define SOLAR_ELEVATION_CIVIL_DUSK_DAWN (-6.0)
/**
* The Sun's elevation at nautical dusk and nautical dawn, measured in degrees.
*/
#define SOLAR_ELEVATION_NAUTICAL_DUSK_DAWN (-12.0)
/**
* The Sun's elevation at astronomical dusk and astronomical dawn, measured in degrees.
*/
#define SOLAR_ELEVATION_ASTRONOMICAL_DUSK_DAWN (-18.0)
/**
* Test whether it is twilight.
*
* @param ELEV:double The current elevation.
* @return 1 if is twilight, 0 otherwise.
*/
#define SOLAR_IS_TWILIGHT(ELEV) ((-18.0 <= (ELEV)) && ((ELEV) <= 0.0))
/**
* Test whether it is civil twilight.
*
* @param ELEV:double The current elevation.
* @return 1 if is civil twilight, 0 otherwise.
*/
#define SOLAR_IS_CIVIL_TWILIGHT(ELEV) ((-6.0 <= (ELEV)) && ((ELEV) <= 0.0))
/**
* Test whether it is nautical twilight.
*
* @param ELEV:double The current elevation.
* @return 1 if is nautical twilight, 0 otherwise.
*/
#define SOLAR_IS_NAUTICAL_TWILIGHT(ELEV) ((-12.0 <= (ELEV)) && ((ELEV) <= -6.0))
/**
* Test whether it is astronomical twilight.
*
* @param ELEV:double The current elevation.
* @return 1 if is astronomical twilight, 0 otherwise.
*/
#define SOLAR_IS_ASTRONOMICAL_TWILIGHT(ELEV) ((-18.0 <= (ELEV)) && ((ELEV) <= -12.0))
/**
* Calculates the Sun's elevation as apparent.
* from a geographical position.
*
* @param latitude The latitude in degrees northwards from
* the equator, negative for southwards.
* @param longitude The longitude in degrees eastwards from
* Greenwich, negative for westwards.
* @return The Sun's apparent elevation as seen, right now,
* from the specified position, measured in degrees.
*
* @throws 0 On success.
* @throws Any error specified for clock_gettime(3) on error.
*/
double solar_elevation(double latitude, double longitude);
/**
* Exit if time the is before year 0 in J2000.
*
* @return 0 on success, -1 on error.
*/
#if defined(TIMETRAVELLER)
int check_timetravel(void);
#else
# define check_timetravel(_) 0
#endif
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