Add some Earth-related functions + bool in jd

src/earth.h

@@ -0,0 +1,73 @@
+/** @file earth.h
+    @brief Functions related to Earth's properties
+
+    From "Astronomical Algorithms", Chapter 10 _The Earth's Globe_
+*/
+#include <stdlib.h>
+#include <math.h>
+
+/**
+* @struct
+* A representation of the Earth
+* with some geometrical properties
+*/
+struct Earth {
+	double a; /*!< The Earth's equatorial radius in km */
+	double f; /*!< The Earth's flattening */
+    double b; /*!< The Earth's polar radius in km */
+	double e; /*!< The eccentricity of Earth's meridian */
+};
+
+/**
+* @struct
+* Representation of geographical
+* latitude
+*/
+struct Latitude {
+    short degrees;
+    short arcmins;
+    double arcsecs;
+};
+/**
+* @struct
+* Representation of a location
+* on the Earth's surface
+*/
+struct Location {
+    struct Latitude lat; /*!< The location's geographical latitude */
+    double h; /*!< Observer's height above sea level in m */
+    double r_sin_phi_p; /*!< Earth's radius times sin(geocentric latitude) */
+    double r_cos_phi_p; /*!< Earth's radius times cos(geocentric latitude) */
+};
+
+struct Earth set_earth_values(struct Earth * earth);
+double lat_to_dec(struct Latitude lat);
+struct Latitude dec_to_lat(double dec_lat);
+struct Location set_location_params(struct Location * loc);
+/**
+* @fn
+* Initializes an Earth structure
+* @param *earth The Earth struct pointer
+*/
+struct Earth set_earth_values(struct Earth * earth) {
+	earth->a = 6378.14; 
+	earth->f = 1 / 298.257; 
+    double f = earth->f;
+    earth->b = earth->a * (1 - earth->f); 
+	earth->e = sqrt(2*f - f*f);
+
+    return *earth;
+}
+/**
+* @fn
+* Convert Latitude to decimal degrees
+* @param lat The Latitude struct (sessagesimal)
+* @returns The converted Latitude number
+*/
+double lat_to_dec(struct Latitude lat) {
+    double dec_minutes = (double)lat.arcmins / 60.0;
+    double dec_seconds = lat.arcsecs / 3600;
+
+    return lat.degrees + dec_minutes + dec_seconds;
+}
+

src/julianday.h

@@ -3,8 +3,8 @@
 
     From "Astronomical Algorithms", Chapter 7
 */
-
 #include <stdlib.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <math.h>
 #include <string.h>
@@ -25,8 +25,7 @@ struct Date date_from_jd(double jd);
 struct Date set_month_str(struct Date *date);
 int date_diff (struct Date first, struct Date second);
 short get_week_day(struct Date date);
-// TODO refactor to Bool...
+bool is_leap_year(short year);
-char is_leap_year(short year);
 short unsigned get_year_day(struct Date date);
 
 /**
@@ -98,7 +97,13 @@ struct Date date_from_jd(double jd) {
 
     return date;
 }
-
+/**
+* @fn
+* Sets the English name for the month in
+* a Date struct
+* @param The Date struct where the month string
+*        should be set
+*/
 struct Date set_month_str(struct Date *date) {
     char* test;
 
@@ -149,6 +154,8 @@ struct Date set_month_str(struct Date *date) {
 }
 /**
 * Returns the date difference in days
+* @param first The first Date (smaller)
+* @param second The second Date (larger)
 */
 int date_diff(struct Date first, struct Date second) {
    double jd_first = jd(first); 
@@ -158,6 +165,7 @@ int date_diff(struct Date first, struct Date second) {
 }
 /**
 * Returns the week day as a number
+* @param date The Date struct to find the week day from
 */
 short get_week_day(struct Date date) {
    // Day should be taken at Oh
@@ -169,12 +177,14 @@ short get_week_day(struct Date date) {
 /**
 * Checks whether a given year is
 * a leap year (Gregorian only!!)
+* @param year The year to check
 */
-char is_leap_year(short year) {
+bool is_leap_year(short year) {
     return (year % 4) == 0;
 }
 /**
 * Returns the day number in the given year
+ * @param date The Date struct to use
 */
 short unsigned get_year_day(struct Date date) {
     short k = is_leap_year(date.year) ? 1 : 2;