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use crateanp;
use ;
/// Greenwich apparent sidereal time, IAU 2000B
///
/// Greenwich apparent sidereal time (consistent with IAU 2000
/// resolutions but using the truncated nutation model IAU 2000B).
///
/// This function is part of the International Astronomical Union's
/// SOFA (Standards of Fundamental Astronomy) software collection.
///
/// Status: support function.
///
/// Given:
/// ```
/// uta,utb double UT1 as a 2-part Julian Date (Notes 1,2)
/// ```
/// Returned (function value):
/// ```
/// double Greenwich apparent sidereal time (radians)
/// ```
/// Notes:
///
/// 1) The UT1 date uta+utb is a Julian Date, apportioned in any
/// convenient way between the argument pair. 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. 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) The result is compatible with the IAU 2000 resolutions, except
/// that accuracy has been compromised for the sake of speed and
/// convenience in two respects:
///
/// . UT is used instead of TDB (or TT) to compute the precession
/// component of GMST and the equation of the equinoxes. This
/// results in errors of order 0.1 mas at present.
///
/// . The IAU 2000B abridged nutation model (McCarthy & Luzum, 2003)
/// is used, introducing errors of up to 1 mas.
///
/// 3) This GAST is compatible with the IAU 2000 resolutions and must be
/// used only in conjunction with other IAU 2000 compatible
/// components such as precession-nutation.
///
/// 4) The result is returned in the range 0 to 2pi.
///
/// 5) The algorithm is from Capitaine et al. (2003) and IERS
/// Conventions 2003.
///
/// Called:
/// ```
/// iauGmst00 Greenwich mean sidereal time, IAU 2000
/// iauEe00b equation of the equinoxes, IAU 2000B
/// iauAnp normalize angle into range 0 to 2pi
/// ```
/// References:
///
/// Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to
/// implement the IAU 2000 definition of UT1", Astronomy &
/// Astrophysics, 406, 1135-1149 (2003)
///
/// McCarthy, D.D. & Luzum, B.J., "An abridged model of the
/// precession-nutation of the celestial pole", Celestial Mechanics &
/// Dynamical Astronomy, 85, 37-49 (2003)
///
/// McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
/// IERS Technical Note No. 32, BKG (2004)
///