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

}