rfa 0.5.9

A port ERFA to Rust.
Documentation 
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use super::{obl06::*, nut06a::*, numat::*};
///  Form the matrix of nutation for a given date, IAU 2006/2000A model.
///
///  Given:
///   * date1,date2 TT as a 2-part Julian Date (Note 1)
///
///  Returned:
///   * rmatn nutation matrix
///
/// # Notes:
///
///  1) The TT date date1+date2 is a Julian Date, apportioned in any
///     convenient way between the two arguments.  For example,
///     JD(TT)=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.
///
///  2) The matrix operates in the sense V(true) = rmatn * V(mean), where
///     the p-vector V(true) is with respect to the true equatorial triad
///     of date and the p-vector V(mean) is with respect to the mean
///     equatorial triad of date.
///
/// # Called:
///    * obl06     mean obliquity, IAU 2006
///    * nut06a    nutation, IAU 2006/2000A
///    * numat     form nutation matrix
///
/// # Reference:
///   * Explanatory Supplement to the Astronomical Almanac,
///     P. Kenneth Seidelmann (ed), University Science Books (1992),
///     Section 3.222-3 (p114).
///
///  This revision:  2021 May 11

pub fn num06a(date1: f64, date2: f64, rmatn: &mut [[f64; 3];3])
{
    let mut dp = 0.0; let mut de =0.0;
 
 
 /* Mean obliquity. */
    let eps = obl06(date1, date2);
 
 /* Nutation components. */
    nut06a(date1, date2, &mut dp, &mut de);
 
 /* Nutation matrix. */
    numat(eps, dp, de, rmatn);
 
 /* Finished. */
 
}