export iauC2teqx
"""
**  Assemble the celestial to terrestrial matrix from equinox-based
**  components (the celestial-to-true matrix, the Greenwich Apparent
**  Sidereal Time and the polar motion matrix).
**
**  This function is part of the International Astronomical Union's
**  SOFA (Standards Of Fundamental Astronomy) software collection.
**
**  Status:  support function.
**
**  Given:
**     rbpn   double[3][3]  celestial-to-true matrix
**     gst    double        Greenwich (apparent) Sidereal Time (radians)
**     rpom   double[3][3]  polar-motion matrix
**
**  Returned:
**     rc2t   double[3][3]  celestial-to-terrestrial matrix (Note 2)
**
**  Notes:
**
**  1) This function constructs the rotation matrix that transforms
**     vectors in the celestial system into vectors in the terrestrial
**     system.  It does so starting from precomputed components, namely
**     the matrix which rotates from celestial coordinates to the
**     true equator and equinox of date, the Greenwich Apparent Sidereal
**     Time and the polar motion matrix.  One use of the present function
**     is when generating a series of celestial-to-terrestrial matrices
**     where only the Sidereal Time changes, avoiding the considerable
**     overhead of recomputing the precession-nutation more often than
**     necessary to achieve given accuracy objectives.
**
**  2) The relationship between the arguments is as follows:
**
**        [TRS] = rpom * R_3(gst) * rbpn * [CRS]
**
**              = rc2t * [CRS]
**
**     where [CRS] is a vector in the Geocentric Celestial Reference
**     System and [TRS] is a vector in the International Terrestrial
**     Reference System (see IERS Conventions 2003).
**
**  Called:
**     iauCr        copy r-matrix
**     iauRz        rotate around Z-axis
**     iauRxr       product of two r-matrices
**
**  Reference:
**
**     McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
**     IERS Technical Note No. 32, BKG (2004)
**
**  This revision:  2013 August 24
**
**  SOFA release 2018-01-30
**
**  Copyright (C) 2018 IAU SOFA Board.  See notes at end.
"""

# void iauC2teqx(double rbpn[3][3], double gst, double rpom[3][3],
#                double rc2t[3][3])

function iauC2teqx(rbpn::AbstractMatrix{<:Real}, gst::Real, rpom::AbstractMatrix{<:Real})

   # Allocate return value
   rc2t = zeros(Float64, 3, 3)

   ccall((:iauC2teqx, libsofa_c), Cvoid, 
         (Ptr{Cdouble}, Cdouble, Ptr{Cdouble},
         Ptr{Cdouble}), 
         convert(Array{Float64, 2}, rbpn'), convert(Float64, gst),
         convert(Array{Float64, 2}, rpom'),
         rc2t)

   return SMatrix{3,3}(rc2t')
end