rfa 0.5.9

A port ERFA to Rust.
Documentation 
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use super::{pr00::*, obl80::*, bp00::*,numat::*};
use crate::vector_matrix::copy_ext::cr;
use crate::vector_matrix::matrix_ops::rxr::rxr;
///  Precession-nutation, IAU 2000 model:  a multi-purpose function,
///  supporting classical (equinox-based) use directly and CIO-based
///  use indirectly.
///
///  Given:
///     * date1,date2  double          TT as a 2-part Julian Date (Note 1)
///     * dpsi,deps    double          nutation (Note 2)
///
///  Returned:
///   * epsa         mean obliquity (Note 3)
///   * rb           frame bias matrix (Note 4)
///   * rp           precession matrix (Note 5)
///   * rbp          bias-precession matrix (Note 6)
///   * rn           nutation matrix (Note 7)
///   * rbpn         GCRS-to-true matrix (Note 8)
///
/// # 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 caller is responsible for providing the nutation components;
///     they are in longitude and obliquity, in radians and are with
///     respect to the equinox and ecliptic of date.  For high-accuracy
///     applications, free core nutation should be included as well as
///     any other relevant corrections to the position of the CIP.
///
///  3) The returned mean obliquity is consistent with the IAU 2000
///     precession-nutation models.
///
///  4) The matrix rb transforms vectors from GCRS to J2000.0 mean
///     equator and equinox by applying frame bias.
///
///  5) The matrix rp transforms vectors from J2000.0 mean equator and
///     equinox to mean equator and equinox of date by applying
///     precession.
///
///  6) The matrix rbp transforms vectors from GCRS to mean equator and
///     equinox of date by applying frame bias then precession.  It is
///     the product rp x rb.
///
///  7) The matrix rn transforms vectors from mean equator and equinox of
///     date to true equator and equinox of date by applying the nutation
///     (luni-solar + planetary).
///
///  8) The matrix rbpn transforms vectors from GCRS to true equator and
///     equinox of date.  It is the product rn x rbp, applying frame
///     bias, precession and nutation in that order.
///
///  9) It is permissible to re-use the same array in the returned
///     arguments.  The arrays are filled in the order given.
///
///  Called:
///   * pr00      IAU 2000 precession adjustments
///   * obl80     mean obliquity, IAU 1980
///   * bp00      frame bias and precession matrices, IAU 2000
///   * cr        copy r-matrix
///   * numat     form nutation matrix
///   * rxr       product of two r-matrices
///
/// # Reference:
///    * Capitaine, N., Chapront, J., Lambert, S. and Wallace, P.,
///      "Expressions for the Celestial Intermediate Pole and Celestial
///      Ephemeris Origin consistent with the IAU 2000A precession-
///      nutation model", Astron.Astrophys. 400, 1145-1154 (2003)
///      n.b. The celestial ephemeris origin (CEO) was renamed "celestial
///      intermediate origin" (CIO) by IAU 2006 Resolution 2.
///
///  This revision:  2021 May 11
pub fn pn00(date1: f64, date2: f64, dpsi: f64, deps: f64,
    epsa: &mut f64,
    rb: &mut [[f64; 3];3], rp: &mut [[f64; 3];3], rbp: &mut [[f64; 3];3],
    rn: &mut [[f64; 3];3], rbpn: &mut [[f64; 3];3])
{
    let mut dpsipr =0.0;let mut depspr =0.0;
    let mut rbpw = [[0.0; 3];3];
    let mut rnw = [[0.0; 3];3];
/* IAU 2000 precession-rate adjustments. */
    pr00(date1, date2, &mut dpsipr, &mut depspr);
 
 /* Mean obliquity, consistent with IAU 2000 precession-nutation. */
    *epsa = obl80(date1, date2) + depspr;
 
 /* Frame bias and precession matrices and their product. */
    bp00(date1, date2, rb, rp, &mut rbpw);
    cr(&rbpw, rbp);
 
 /* Nutation matrix. */
    numat(*epsa, dpsi, deps, &mut rnw);
    cr(&rnw, rn);
 
 /* Bias-precession-nutation matrix (classical). */
    rxr(&rnw, &rbpw, rbpn);
 
 /* Finished. */
 
 }