Add equations 1-17

Starting off with function soup

Cargo.toml

@@ -9,6 +9,7 @@ keywords = ["astronomy", "physics", "solar_tracking", "solar_power", "CPV"]
 categories = ["algorithms", "science", "aerospace"]
 
 [dependencies]
+num = "0.4.1"
 
 [lib]
 name = "solaris"

src/lib.rs

@@ -1,3 +1,114 @@
+use num::{Float, NumCast};
+
+// (1) atan2, but the undefined (0, 0) is defined as 0
+pub fn fast_atan2<F: Float>(y: F, x: F) -> F {
+    /*
+    if x > 0 {
+
+    } else if x == 0 {
+    } else if x < 0 {
+    }
+    */
+    NumCast::from(0).unwrap()
+}
+
+// TODO: placeholder
+/// Julian days since epoch year 2000.0.
+type JD2000 = f64;
+//// Centuries since epoch year 2000.0
+type JC2000 = f64;
+
+/// (2) Simon et al., 1994
+/// λ0
+pub fn sun_mean_longitude<F: Float>(t_Jc: JC2000) -> F {
+    NumCast::from(t_Jc).unwrap()
+}
+
+/// (3) Chapront-Touze and Chapront, 1988
+/// M
+pub fn mean_anomaly<F: Float>(t_Jc: JC2000) -> F {
+    NumCast::from(t_Jc).unwrap()
+}
+
+/// (4) Meeus 1998
+/// C
+pub fn sun_equation_centre<F: Float>(t_Jc: JC2000) -> F {
+    NumCast::from(t_Jc).unwrap()
+}
+
+/// (5)
+/// λ_{base}
+pub fn sun_base_longitude<F: Float>(t_Jc: JC2000) -> F {
+    sun_mean_longitude::<F>(t_Jc) + sun_equation_centre::<F>(t_Jc)
+}
+
+/// (6) Chapront-Touze and Chapront, 1988
+/// Ω
+pub fn moon_longitude_mean_ascending_node<F: Float>(t_Jc: JC2000) -> F {
+    NumCast::from(t_Jc).unwrap()
+}
+
+/// (7) Seidelmann, 1982
+/// ∆ψ
+pub fn earth_nutation_in_longitude<F: Float>(t_Jc: JC2000) -> F {
+    NumCast::from(t_Jc).unwrap()
+}
+
+/// (8), (9), (10) Simon et al., 1994
+/// R
+pub fn earth_accurate_semimajor_axis<F: Float>(t_Jc: JC2000) -> F {
+    NumCast::from(t_Jc).unwrap()
+}
+
+/// (11)
+/// R
+pub fn earth_approx_semimajor_axis<F: Float>(t_Jc: JC2000) -> F {
+    NumCast::from(1.0000010178).unwrap()
+}
+
+/// (12) Kovalevsky and Seidelmann, 2004
+/// ∆λ
+pub fn annual_abberration<F: Float>(R: F) -> F {
+    NumCast::from(R).unwrap()
+}
+
+/// (13)
+/// λ
+/// Longitude of the sun, correcting for nutation and aberration
+pub fn sun_actual_longitude<F: Float>(t_Jc: JC2000) -> F {
+    sun_base_longitude::<F>(t_Jc)
+        + annual_abberration::<F>(earth_accurate_semimajor_axis::<F>(t_Jc))
+        + earth_nutation_in_longitude::<F>(t_Jc)
+}
+
+/// (14) Ecliptical latitude
+/// β
+/// Not extreme accuracy needed && Sun always near ecliptic, ecliptical latitude can = 0
+pub fn sun_approx_ecliptical_latitude<F: Float>() -> F {
+    NumCast::from(0).unwrap()
+}
+
+/// (15) Meeus, 1998
+/// ε0
+/// Mean obliquity
+pub fn mean_obliquity<F: Float>(t_Jc: JC2000) -> F {
+    NumCast::from(t_Jc).unwrap()
+}
+
+/// (16) Seidelmann, 1982
+/// ∆ε
+/// Nutation in obliquity
+pub fn nutation_obliquity<F: Float>(Omega: F) -> F {
+    NumCast::from(Omega).unwrap()
+}
+
+/// (17)
+/// ε
+/// Obliquity of the ecliptic
+pub fn obliquity_ecliptic<F: Float>(t_Jc: JC2000, Omega: F) -> F {
+    NumCast::from(t_Jc).unwrap()
+}
+
 pub fn add(left: usize, right: usize) -> usize {
     left + right
 }