pvxpv.c

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#include "erfa.h"

void eraPvxpv(double a[2][3], double b[2][3], double axb[2][3])
/*
**  - - - - - - - - -
**   e r a P v x p v
**  - - - - - - - - -
**
**  Outer (=vector=cross) product of two pv-vectors.
**
**  Given:
**     a        double[2][3]      first pv-vector
**     b        double[2][3]      second pv-vector
**
**  Returned:
**     axb      double[2][3]      a x b
**
**  Notes:
**
**  1) If the position and velocity components of the two pv-vectors are
**     ( ap, av ) and ( bp, bv ), the result, a x b, is the pair of
**     vectors ( ap x bp, ap x bv + av x bp ).  The two vectors are the
**     cross-product of the two p-vectors and its derivative.
**
**  2) It is permissible to re-use the same array for any of the
**     arguments.
**
**  Called:
**     eraCpv       copy pv-vector
**     eraPxp       vector product of two p-vectors
**     eraPpp       p-vector plus p-vector
**
**  Copyright (C) 2013-2015, NumFOCUS Foundation.
**  Derived, with permission, from the SOFA library.  See notes at end of file.
*/
{
   double wa[2][3], wb[2][3], axbd[3], adxb[3];

/* Make copies of the inputs. */
   eraCpv(a, wa);
   eraCpv(b, wb);

/* a x b = position part of result. */
   eraPxp(wa[0], wb[0], axb[0]);

/* a x bdot + adot x b = velocity part of result. */
   eraPxp(wa[0], wb[1], axbd);
   eraPxp(wa[1], wb[0], adxb);
   eraPpp(axbd, adxb, axb[1]);

   return;

}
/*----------------------------------------------------------------------
**  
**  
**  Copyright (C) 2013-2015, 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
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**    distribution.
**  
**  3 Neither the name of the Standards Of Fundamental Astronomy Board,
**    the International Astronomical Union nor the names of its
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**    from this software without specific prior written permission.
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*/