#include "sofa.h"

void iauPfw06(double date1, double date2,
              double *gamb, double *phib, double *psib, double *epsa)
/*
**  - - - - - - - - -
**   i a u P f w 0 6
**  - - - - - - - - -
**
**  Precession angles, IAU 2006 (Fukushima-Williams 4-angle formulation).
**
**  This function is part of the International Astronomical Union's
**  SOFA (Standards Of Fundamental Astronomy) software collection.
**
**  Status:  canonical model.
**
**  Given:
**     date1,date2  double   TT as a 2-part Julian Date (Note 1)
**
**  Returned:
**     gamb         double   F-W angle gamma_bar (radians)
**     phib         double   F-W angle phi_bar (radians)
**     psib         double   F-W angle psi_bar (radians)
**     epsa         double   F-W angle epsilon_A (radians)
**
**  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) Naming the following points:
**
**           e = J2000.0 ecliptic pole,
**           p = GCRS pole,
**           E = mean ecliptic pole of date,
**     and   P = mean pole of date,
**
**     the four Fukushima-Williams angles are as follows:
**
**        gamb = gamma_bar = epE
**        phib = phi_bar = pE
**        psib = psi_bar = pEP
**        epsa = epsilon_A = EP
**
**  3) The matrix representing the combined effects of frame bias and
**     precession is:
**
**        PxB = R_1(-epsa).R_3(-psib).R_1(phib).R_3(gamb)
**
**  4) The matrix representing the combined effects of frame bias,
**     precession and nutation is simply:
**
**        NxPxB = R_1(-epsa-dE).R_3(-psib-dP).R_1(phib).R_3(gamb)
**
**     where dP and dE are the nutation components with respect to the
**     ecliptic of date.
**
**  Reference:
**
**     Hilton, J. et al., 2006, Celest.Mech.Dyn.Astron. 94, 351
**
**  Called:
**     iauObl06     mean obliquity, IAU 2006
**
**  This revision:  2013 June 18
**
**  SOFA release 2016-05-03
**
**  Copyright (C) 2016 IAU SOFA Board.  See notes at end.
*/
{
   double t;


/* Interval between fundamental date J2000.0 and given date (JC). */
   t = ((date1 - DJ00) + date2) / DJC;

/* P03 bias+precession angles. */
   *gamb = (    -0.052928     +
           (    10.556378     +
           (     0.4932044    +
           (    -0.00031238   +
           (    -0.000002788  +
           (     0.0000000260 )
           * t) * t) * t) * t) * t) * DAS2R;
   *phib = ( 84381.412819     +
           (   -46.811016     +
           (     0.0511268    +
           (     0.00053289   +
           (    -0.000000440  +
           (    -0.0000000176 )
           * t) * t) * t) * t) * t) * DAS2R;
   *psib = (    -0.041775     +
           (  5038.481484     +
           (     1.5584175    +
           (    -0.00018522   +
           (    -0.000026452  +
           (    -0.0000000148 )
           * t) * t) * t) * t) * t) * DAS2R;
   *epsa =  iauObl06(date1, date2);

   return;

/*----------------------------------------------------------------------
**
**  Copyright (C) 2016
**  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
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**     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
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**     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
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**                 Somerset, TA1 2DN
**                 United Kingdom
**
**--------------------------------------------------------------------*/
}