rfa 0.5.9

A port ERFA to Rust.
Documentation 
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use super::{pnm06a::pnm06a, bpn2xy::*, s06::*, c2ixys::*};
///  Form the celestial-to-intermediate matrix for a given date using the
///  IAU 2006 precession and IAU 2000A nutation models.
///
///  Given:
///     date1,date2 double       TT as a 2-part Julian Date (Note 1)
///
///  Returned:
///     rc2i        double[3][3] celestial-to-intermediate matrix (Note 2)
///
///  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 rc2i is the first stage in the transformation from
///     celestial to terrestrial coordinates:
///
///        [TRS]  =  RPOM * R_3(ERA) * rc2i * [CRS]
///
///               =  RC2T * [CRS]
///
///     where [CRS] is a vector in the Geocentric Celestial Reference
///     System and [TRS] is a vector in the International Terrestrial
///     Reference System (see IERS Conventions 2003), ERA is the Earth
///     Rotation Angle and RPOM is the polar motion matrix.
///
///  Called:
///     eraPnm06a    classical NPB matrix, IAU 2006/2000A
///     eraBpn2xy    extract CIP X,Y coordinates from NPB matrix
///     eraS06       the CIO locator s, given X,Y, IAU 2006
///     eraC2ixys    celestial-to-intermediate matrix, given X,Y and s
///
///  References:
///
///     McCarthy, D. D., Petit, G. (eds.), 2004, IERS Conventions (2003),
///     IERS Technical Note No. 32, BKG
///
///  This revision:  2021 May 11
///  fn ursa_c2i06a(date1: f64, date2: f64, rc2i: &mut [[f64; 3]; 3]){todo!()}
pub fn c2i06a(date1: f64, date2: f64, rc2i: &mut [[f64; 3]; 3])
{
    let mut rbpn = [[0.0; 3]; 3]; let mut x =0.0; let mut y =0.0; 
 
 
 /* Obtain the celestial-to-true matrix (IAU 2006/2000A). */
    pnm06a(date1, date2, &mut rbpn);
 
 /* Extract the X,Y coordinates. */
    bpn2xy(&rbpn, &mut x, &mut y);
 
 /* Obtain the CIO locator. */
    let s = s06(date1, date2, x, y);
 
 /* Form the celestial-to-intermediate matrix. */
    c2ixys(x, y, s, rc2i);
 
 /* Finished. */
 
 }