1 files changed, 130 insertions, 0 deletions
diff --git a/ast/erfa/fw2xy.c b/ast/erfa/fw2xy.c
new file mode 100644
index 0000000..b4e0693
--- /dev/null
+++ b/ast/erfa/fw2xy.c
@@ -0,0 +1,130 @@
+#include "erfa.h"
+
+void eraFw2xy(double gamb, double phib, double psi, double eps,
+              double *x, double *y)
+/*
+**  - - - - - - - - -
+**   e r a F w 2 x y
+**  - - - - - - - - -
+**
+**  CIP X,Y given Fukushima-Williams bias-precession-nutation angles.
+**
+**  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:
+**     eraFw2m      F-W angles to r-matrix
+**     eraBpn2xy    extract CIP X,Y coordinates from NPB matrix
+**
+**  Reference:
+**
+**     Hilton, J. et al., 2006, Celest.Mech.Dyn.Astron. 94, 351
+**
+**  Copyright (C) 2013-2016, NumFOCUS Foundation.
+**  Derived, with permission, from the SOFA library.  See notes at end of file.
+*/
+{
+   double r[3][3];
+
+
+/* Form NxPxB matrix. */
+   eraFw2m(gamb, phib, psi, eps, r);
+
+/* Extract CIP X,Y. */
+   eraBpn2xy(r, x, y);
+
+   return;
+
+}
+/*----------------------------------------------------------------------
+**  
+**  
+**  Copyright (C) 2013-2016, NumFOCUS Foundation.
+**  All rights reserved.
+**  
+**  This library is derived, with permission, from the International
+**  Astronomical Union's "Standards of Fundamental Astronomy" library,
+**  available from http://www.iausofa.org.
+**  
+**  The ERFA version is intended to retain identical functionality to
+**  the SOFA library, but made distinct through different function and
+**  file names, as set out in the SOFA license conditions.  The SOFA
+**  original has a role as a reference standard for the IAU and IERS,
+**  and consequently redistribution is permitted only in its unaltered
+**  state.  The ERFA version is not subject to this restriction and
+**  therefore can be included in distributions which do not support the
+**  concept of "read only" software.
+**  
+**  Although the intent is to replicate the SOFA API (other than
+**  replacement of prefix names) and results (with the exception of
+**  bugs;  any that are discovered will be fixed), SOFA is not
+**  responsible for any errors found in this version of the library.
+**  
+**  If you wish to acknowledge the SOFA heritage, please acknowledge
+**  that you are using a library derived from SOFA, rather than SOFA
+**  itself.
+**  
+**  
+**  TERMS AND CONDITIONS
+**  
+**  Redistribution and use in source and binary forms, with or without
+**  modification, are permitted provided that the following conditions
+**  are met:
+**  
+**  1 Redistributions of source code must retain the above copyright
+**    notice, this list of conditions and the following disclaimer.
+**  
+**  2 Redistributions in binary form must reproduce the above copyright
+**    notice, this list of conditions and the following disclaimer in
+**    the documentation and/or other materials provided with the
+**    distribution.
+**  
+**  3 Neither the name of the Standards Of Fundamental Astronomy Board,
+**    the International Astronomical Union nor the names of its
+**    contributors may be used to endorse or promote products derived
+**    from this software without specific prior written permission.
+**  
+**  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+**  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+**  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+**  FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+**  COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+**  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+**  BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+**  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+**  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+**  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+**  ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+**  POSSIBILITY OF SUCH DAMAGE.
+**  
+*/