#include "sofa.h"
void iauFw2xy(double gamb, double phib, double psi, double eps,
double *x, double *y)
/*
** - - - - - - - - -
** i a u F w 2 x y
** - - - - - - - - -
**
** CIP X,Y given Fukushima-Williams bias-precession-nutation angles.
**
** This function is part of the International Astronomical Union's
** SOFA (Standards Of Fundamental Astronomy) software collection.
**
** Status: support function.
**
** Given:
** gamb double F-W angle gamma_bar (radians)
** phib double F-W angle phi_bar (radians)
** psi double F-W angle psi (radians)
** eps double F-W angle epsilon (radians)
**
** Returned:
** x,y double CIP unit vector X,Y
**
** 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(-epsA).R_3(-psi).R_1(phib).R_3(gamb)
**
** The returned values x,y are elements [2][0] and [2][1] of the
** matrix. Near J2000.0, they are essentially angles in radians.
**
** Called:
** iauFw2m F-W angles to r-matrix
** iauBpn2xy extract CIP X,Y coordinates from NPB matrix
**
** Reference:
**
** Hilton, J. et al., 2006, Celest.Mech.Dyn.Astron. 94, 351
**
** This revision: 2021 May 11
**
** SOFA release 2021-05-12
**
** Copyright (C) 2021 IAU SOFA Board. See notes at end.
*/
{
double r[3][3];
/* Form NxPxB matrix. */
iauFw2m(gamb, phib, psi, eps, r);
/* Extract CIP X,Y. */
iauBpn2xy(r, x, y);
/* Finished. */
/*----------------------------------------------------------------------
**
** Copyright (C) 2021
** 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
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**
** 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
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**
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**
** 6. The provision of any version of the SOFA software under the terms
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*
** In any published work or commercial product which uses the SOFA
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** appreciated.
**
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** follows:
**
** By email: sofa@ukho.gov.uk
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**
**--------------------------------------------------------------------*/
}