rfa 0.5.9

A port ERFA to Rust.
Documentation 
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use super::gst06::*;
use crate::prec_nut::pnm06a::*;
///  Greenwich apparent sidereal time (consistent with IAU 2000 and 2006
///  resolutions).
///
///  Given:
///   * uta,utb UT1 as a 2-part Julian Date (Notes 1,2)
///   * tta,ttb TT as a 2-part Julian Date (Notes 1,2)
///
///  Returned (function value):
///   * Greenwich apparent sidereal time (radians)
///
/// # Notes:
///
///  1) The UT1 and TT dates uta+utb and tta+ttb respectively, are both
///     Julian Dates, apportioned in any convenient way between the
///     argument pairs.  For example, JD(UT1)=2450123.7 could be
///     expressed in any of these ways, among others:
///
///     |    uta      |      utb     |                      |
///     |-------------|--------------|----------------------|
///     |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 (in the case of UT;  the TT is not at all critical
///     in this respect).  The J2000 and MJD methods are good compromises
///     between resolution and convenience.  For UT, the date & time
///     method is best matched to the algorithm that is used by the Earth
///     rotation angle function, called internally:  maximum precision is
///     delivered when the uta argument is for 0hrs UT1 on the day in
///     question and the utb argument lies in the range 0 to 1, or vice
///     versa.
///
///  2) Both UT1 and TT are required, UT1 to predict the Earth rotation
///     and TT to predict the effects of precession-nutation.  If UT1 is
///     used for both purposes, errors of order 100 microarcseconds
///     result.
///
///  3) This GAST is compatible with the IAU 2000/2006 resolutions and
///     must be used only in conjunction with IAU 2006 precession and
///     IAU 2000A nutation.
///
///  4) The result is returned in the range 0 to 2pi.
///
/// # Called:
///     pnm06a    classical NPB matrix, IAU 2006/2000A
///     gst06     Greenwich apparent ST, IAU 2006, given NPB matrix
///
/// # Reference:
///   * Wallace, P.T. & Capitaine, N., 2006, Astron.Astrophys. 459, 981
///
///  This revision:  2021 May 11
pub fn gst06a(uta: f64, utb: f64, tta: f64, ttb: f64)->f64
{
    let mut rnpb = [[0.0; 3]; 3];
 
 
 /* Classical nutation x precession x bias matrix, IAU 2000A. */
    pnm06a(tta, ttb, &mut rnpb);
 
 /* Greenwich apparent sidereal time. */
    gst06(uta, utb, tta, ttb, &rnpb)
 
 /* Finished. */
 
 }