rfa 0.5.9

A port ERFA to Rust.
Documentation 
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use crate::{rfam::*, vector_matrix::angle_ops::anp::anp};
use super::era00::*;
///  Greenwich mean sidereal time (consistent with IAU 2006 precession).
///
///  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 mean 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=2450123.7 could be expressed in
///     any of these ways, among others:
///
///     |    Part A   |    Part B    |
///     |-------------|--------------|----------------------|
///     |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.  If UT1 is used for
///     both purposes, errors of order 100 microarcseconds result.
///
///  3) This GMST is compatible with the IAU 2006 precession and must not
///     be used with other precession models.
///
///  4) The result is returned in the range 0 to 2pi.
///
/// # Called:
///   * era00     Earth rotation angle, IAU 2000
///   * anp       normalize angle into range 0 to 2pi
///
/// # Reference:
///   * Capitaine, N., Wallace, P.T. & Chapront, J., 2005,
///     Astron.Astrophys. 432, 355
///
///  This revision:  2021 May 11
pub fn gmst06(uta: f64, utb: f64, tta: f64, ttb: f64)->f64
{
 
 /* TT Julian centuries since J2000.0. */
    let t = ((tta - URSA_DJ00) + ttb) / URSA_DJC;
 
 /* Greenwich mean sidereal time, IAU 2006. */
   anp(era00(uta, utb) +
                   (    0.014506     +
                   (  4612.156534    +
                   (     1.3915817   +
                   (    -0.00000044  +
                   (    -0.000029956 +
                   (    -0.0000000368 )
           * t) * t) * t) * t) * t) * URSA_DAS2R)
 
 /* Finished. */
 
 }