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use crate::pnp::bp00;
/// Precession matrix (including frame bias) from GCRS to a specified
/// date, IAU 2000 model.
///
/// Given:
/// date1,date2 f64 TT as a 2-part Julian Date (Note 1)
///
/// Returned (function value):
/// [[f64; 3]; 3] bias-precession 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 operates in the sense V(date) = rbp * V(GCRS), where
/// the p-vector V(GCRS) is with respect to the Geocentric Celestial
/// Reference System (IAU, 2000) and the p-vector V(date) is with
/// respect to the mean equatorial triad of the given date.
///
/// Called:
/// iauBp00 frame bias and precession matrices, IAU 2000
///
/// Reference:
///
/// IAU: Trans. International Astronomical Union, Vol. XXIVB; Proc.
/// 24th General Assembly, Manchester, UK. Resolutions B1.3, B1.6.
/// (2000)
pub fn pmat00(date1: f64, date2: f64) -> [[f64; 3]; 3] {
/* Obtain the required matrix (discarding others). */
let (_, _, rbp) = bp00(date1, date2);
rbp
}