rfa 0.5.9

A port ERFA to Rust.
Documentation 
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use crate::vector_matrix::{init::ir::*, build_rotations::{rz::*, rx::*}};
///  Form rotation matrix given the Fukushima-Williams angles.
///
///  Given:
///   * gamb     F-W angle gamma_bar (radians)
///   * phib     F-W angle phi_bar (radians)
///   * psi      F-W angle psi (radians)
///   * eps      F-W angle epsilon (radians)
///
///  Returned:
///   * r rotation matrix
///
/// # Notes:
///
///  1) Naming the following points:
///
///           e = J2000.0 ecliptic pole,
///           p = GCRS pole,
///           E = ecliptic pole of date,
///     and   P = CIP,
///
///     the four Fukushima-Williams angles are as follows:
///
///        gamb = gamma = epE
///        phib = phi = pE
///        psi = psi = pEP
///        eps = epsilon = EP
///
///  2) The matrix representing the combined effects of frame bias,
///     precession and nutation is:
///
///        NxPxB = R_1(-eps).R_3(-psi).R_1(phib).R_3(gamb)
///
///  3) The present function can construct three different matrices,
///     depending on which angles are supplied as the arguments gamb,
///     phib, psi and eps:
///
///     o  To obtain the nutation x precession x frame bias matrix,
///        first generate the four precession angles known conventionally
///        as gamma_bar, phi_bar, psi_bar and epsilon_A, then generate
///        the nutation components Dpsi and Depsilon and add them to
///        psi_bar and epsilon_A, and finally call the present function
///        using those four angles as arguments.
///
///     o  To obtain the precession x frame bias matrix, generate the
///        four precession angles and call the present function.
///
///     o  To obtain the frame bias matrix, generate the four precession
///        angles for date J2000.0 and call the present function.
///
///     The nutation-only and precession-only matrices can if necessary
///     be obtained by combining these three appropriately.
///
/// # Called:
///    * ir        initialize r-matrix to identity
///    * rz        rotate around Z-axis
///    * rx        rotate around X-axis
///
/// # References:
///    * Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855
///    * Hilton, J. et al., 2006, Celest.Mech.Dyn.Astron. 94, 351
///
///  This revision:  2021 May 11

pub fn fw2m(gamb:f64, phib: f64, psi: f64, eps: f64,
    r: &mut[[f64;3];3])

{
    /* Construct the matrix. */
       ir(r);
       rz(gamb, r);
       rx(phib, r);
       rz(-psi, r);
       rx(-eps, r);
    
    /* Finished. */
    
}