#include "sofa.h"

void iauPn00(double date1, double date2, double dpsi, double deps,
             double *epsa,
             double rb[3][3], double rp[3][3], double rbp[3][3],
             double rn[3][3], double rbpn[3][3])
/*
**  - - - - - - - -
**   i a u P n 0 0
**  - - - - - - - -
**
**  Precession-nutation, IAU 2000 model:  a multi-purpose function,
**  supporting classical (equinox-based) use directly and CIO-based
**  use indirectly.
**
**  This function is part of the International Astronomical Union's
**  SOFA (Standards Of Fundamental Astronomy) software collection.
**
**  Status:  support function.
**
**  Given:
**     date1,date2  double          TT as a 2-part Julian Date (Note 1)
**     dpsi,deps    double          nutation (Note 2)
**
**  Returned:
**     epsa         double          mean obliquity (Note 3)
**     rb           double[3][3]    frame bias matrix (Note 4)
**     rp           double[3][3]    precession matrix (Note 5)
**     rbp          double[3][3]    bias-precession matrix (Note 6)
**     rn           double[3][3]    nutation matrix (Note 7)
**     rbpn         double[3][3]    GCRS-to-true matrix (Note 8)
**
**  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 caller is responsible for providing the nutation components;
**     they are in longitude and obliquity, in radians and are with
**     respect to the equinox and ecliptic of date.  For high-accuracy
**     applications, free core nutation should be included as well as
**     any other relevant corrections to the position of the CIP.
**
**  3) The returned mean obliquity is consistent with the IAU 2000
**     precession-nutation models.
**
**  4) The matrix rb transforms vectors from GCRS to J2000.0 mean
**     equator and equinox by applying frame bias.
**
**  5) The matrix rp transforms vectors from J2000.0 mean equator and
**     equinox to mean equator and equinox of date by applying
**     precession.
**
**  6) The matrix rbp transforms vectors from GCRS to mean equator and
**     equinox of date by applying frame bias then precession.  It is
**     the product rp x rb.
**
**  7) The matrix rn transforms vectors from mean equator and equinox of
**     date to true equator and equinox of date by applying the nutation
**     (luni-solar + planetary).
**
**  8) The matrix rbpn transforms vectors from GCRS to true equator and
**     equinox of date.  It is the product rn x rbp, applying frame
**     bias, precession and nutation in that order.
**
**  9) It is permissible to re-use the same array in the returned
**     arguments.  The arrays are filled in the order given.
**
**  Called:
**     iauPr00      IAU 2000 precession adjustments
**     iauObl80     mean obliquity, IAU 1980
**     iauBp00      frame bias and precession matrices, IAU 2000
**     iauCr        copy r-matrix
**     iauNumat     form nutation matrix
**     iauRxr       product of two r-matrices
**
**  Reference:
**
**     Capitaine, N., Chapront, J., Lambert, S. and Wallace, P.,
**     "Expressions for the Celestial Intermediate Pole and Celestial
**     Ephemeris Origin consistent with the IAU 2000A precession-
**     nutation model", Astron.Astrophys. 400, 1145-1154 (2003)
**
**     n.b. The celestial ephemeris origin (CEO) was renamed "celestial
**          intermediate origin" (CIO) by IAU 2006 Resolution 2.
**
**  This revision:  2013 June 18
**
**  SOFA release 2020-07-21
**
**  Copyright (C) 2020 IAU SOFA Board.  See notes at end.
*/
{
   double dpsipr, depspr, rbpw[3][3], rnw[3][3];


/* IAU 2000 precession-rate adjustments. */
   iauPr00(date1, date2, &dpsipr, &depspr);

/* Mean obliquity, consistent with IAU 2000 precession-nutation. */
   *epsa = iauObl80(date1, date2) + depspr;

/* Frame bias and precession matrices and their product. */
   iauBp00(date1, date2, rb, rp, rbpw);
   iauCr(rbpw, rbp);

/* Nutation matrix. */
   iauNumat(*epsa, dpsi, deps, rnw);
   iauCr(rnw, rn);

/* Bias-precession-nutation matrix (classical). */
   iauRxr(rnw, rbpw, rbpn);

   return;

/*----------------------------------------------------------------------
**
**  Copyright (C) 2020
**  Standards Of Fundamental Astronomy Board
**  of the International Astronomical Union.
**
**  =====================
**  SOFA Software License
**  =====================
**
**  NOTICE TO USER:
**
**  BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
**  CONDITIONS WHICH APPLY TO ITS USE.
**
**  1. The Software is owned by the IAU SOFA Board ("SOFA").
**
**  2. Permission is granted to anyone to use the SOFA software for any
**     purpose, including commercial applications, free of charge and
**     without payment of royalties, subject to the conditions and
**     restrictions listed below.
**
**  3. You (the user) may copy and distribute SOFA source code to others,
**     and use and adapt its code and algorithms in your own software,
**     on a world-wide, royalty-free basis.  That portion of your
**     distribution that does not consist of intact and unchanged copies
**     of SOFA source code files is a "derived work" that must comply
**     with the following requirements:
**
**     a) Your work shall be marked or carry a statement that it
**        (i) uses routines and computations derived by you from
**        software provided by SOFA under license to you; and
**        (ii) does not itself constitute software provided by and/or
**        endorsed by SOFA.
**
**     b) The source code of your derived work must contain descriptions
**        of how the derived work is based upon, contains and/or differs
**        from the original SOFA software.
**
**     c) The names of all routines in your derived work shall not
**        include the prefix "iau" or "sofa" or trivial modifications
**        thereof such as changes of case.
**
**     d) The origin of the SOFA components of your derived work must
**        not be misrepresented;  you must not claim that you wrote the
**        original software, nor file a patent application for SOFA
**        software or algorithms embedded in the SOFA software.
**
**     e) These requirements must be reproduced intact in any source
**        distribution and shall apply to anyone to whom you have
**        granted a further right to modify the source code of your
**        derived work.
**
**     Note that, as originally distributed, the SOFA software is
**     intended to be a definitive implementation of the IAU standards,
**     and consequently third-party modifications are discouraged.  All
**     variations, no matter how minor, must be explicitly marked as
**     such, as explained above.
**
**  4. You shall not cause the SOFA software to be brought into
**     disrepute, either by misuse, or use for inappropriate tasks, or
**     by inappropriate modification.
**
**  5. The SOFA software is provided "as is" and SOFA makes no warranty
**     as to its use or performance.   SOFA does not and cannot warrant
**     the performance or results which the user may obtain by using the
**     SOFA software.  SOFA makes no warranties, express or implied, as
**     to non-infringement of third party rights, merchantability, or
**     fitness for any particular purpose.  In no event will SOFA be
**     liable to the user for any consequential, incidental, or special
**     damages, including any lost profits or lost savings, even if a
**     SOFA representative has been advised of such damages, or for any
**     claim by any third party.
**
**  6. The provision of any version of the SOFA software under the terms
**     and conditions specified herein does not imply that future
**     versions will also be made available under the same terms and
**     conditions.
*
**  In any published work or commercial product which uses the SOFA
**  software directly, acknowledgement (see www.iausofa.org) is
**  appreciated.
**
**  Correspondence concerning SOFA software should be addressed as
**  follows:
**
**      By email:  sofa@ukho.gov.uk
**      By post:   IAU SOFA Center
**                 HM Nautical Almanac Office
**                 UK Hydrographic Office
**                 Admiralty Way, Taunton
**                 Somerset, TA1 2DN
**                 United Kingdom
**
**--------------------------------------------------------------------*/
}
