rfa 0.5.9

A port ERFA to Rust.
Documentation 
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use crate::rfam::*;
use crate::vector_matrix::angle_ops::anpm::anpm;
use crate::prec_nut::obl80::*;
use crate::prec_nut::nut80::*;
use crate::utils::*;
///  Equation of the equinoxes, IAU 1994 model.
///
///  Given:
///   * date1,date2 TDB date (Note 1)
///
///  Returned (function value):
///   * equation of the equinoxes (Note 2)
///
/// # Notes:
///
/// 1) The TDB date date1+date2 is a Julian Date, apportioned in any
///    convenient way between the two arguments.  For example,
///    JD(TDB)=2450123.7 could be expressed in any of these ways,
///    among others:
///
///    |    date1    |      date2   |                      |
///    |-------------|--------------|----------------------|
///    |2450123.7    |       0.0    |  (JD method)         |
///    |2451545.0    |   -1421.3    |  (J2000 method)      |
///    |2400000.5    |   50123.2    |  (MJD method)        |
///    |2450123.5    |       0.2    | (date & time method) |
///
///    The JD method is the most natural and convenient to use in
///    cases where the loss of several decimal digits of resolution
///    is acceptable.  The J2000 method is best matched to the way
///    the argument is handled internally and will deliver the
///    optimum resolution.  The MJD method and the date & time methods
///    are both good compromises between resolution and convenience.
///
///     The JD method is the most natural and convenient to use in
///     cases where the loss of several decimal digits of resolution
///     is acceptable.  The J2000 method is best matched to the way
///     the argument is handled internally and will deliver the
///     optimum resolution.  The MJD method and the date & time methods
///     are both good compromises between resolution and convenience.
///
///  2) The result, which is in radians, operates in the following sense:
///
///        Greenwich apparent ST = GMST + equation of the equinoxes
///
/// # Called:
///   * anpm      normalize angle into range +/- pi
///   * nut80     nutation, IAU 1980
///   * obl80     mean obliquity, IAU 1980
///
/// # References:
///    * IAU Resolution C7, Recommendation 3 (1994).
///    * Capitaine, N. & Gontier, A.-M., 1993, Astron.Astrophys., 275,
///      645-650.
///
///  This revision:  2021 May 11
pub fn eqeq94(date1: f64, date2: f64)->f64
{
   let mut dpsi = 0.0; let mut deps = 0.0;


/* Interval between fundamental epoch J2000.0 and given date (JC). */
   let t = ((date1 - URSA_DJ00) + date2) / URSA_DJC;

/* Longitude of the mean ascending node of the lunar orbit on the */
/* ecliptic, measured from the mean equinox of date. */
   let om = anpm((450160.280 + (-482890.539
           + (7.455 + 0.008 * t) * t) * t) * URSA_DAS2R
           + (-5.0 * t) % 1.0 * URSA_D2PI);

/* Nutation components and mean obliquity. */
   nut80(date1, date2, &mut dpsi, &mut deps);
   let eps0 = obl80(date1, date2);

/* Equation of the equinoxes. */
   dpsi*cos(eps0) + URSA_DAS2R*(0.00264*sin(om) + 0.000063*sin(om+om))

/* Finished. */

}