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use crateanp;
use ;
/// Greenwich apparent sidereal time, IAU 1994
///
/// Greenwich apparent sidereal time (consistent with IAU 1982/94
/// resolutions).
///
/// 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 1982 and 1994 resolutions,
/// except that accuracy has been compromised for the sake of
/// convenience in that UT is used instead of TDB (or TT) to compute
/// the equation of the equinoxes.
///
/// 3) This GAST must be used only in conjunction with contemporaneous
/// IAU standards such as 1976 precession, 1980 obliquity and 1982
/// nutation. It is not compatible with the IAU 2000 resolutions.
///
/// 4) The result is returned in the range 0 to 2pi.
///
/// Called:
/// ```
/// iauGmst82 Greenwich mean sidereal time, IAU 1982
/// iauEqeq94 equation of the equinoxes, IAU 1994
/// iauAnp normalize angle into range 0 to 2pi
/// ```
/// References:
///
/// Explanatory Supplement to the Astronomical Almanac,
/// P. Kenneth Seidelmann (ed), University Science Books (1992)
///
/// IAU Resolution C7, Recommendation 3 (1994)
///