rxr.c

#include "erfa.h"

void eraRxr(double a[3][3], double b[3][3], double atb[3][3])
/*
**  - - - - - - -
**   e r a R x r
**  - - - - - - -
**
**  Multiply two r-matrices.
**
**  Given:
**     a        double[3][3]    first r-matrix
**     b        double[3][3]    second r-matrix
**
**  Returned:
**     atb      double[3][3]    a * b
**
**  Note:
**     It is permissible to re-use the same array for any of the
**     arguments.
**
**  Called:
**     eraCr        copy r-matrix
**
**  This revision:  2021 May 11
**
**  Copyright (C) 2013-2023, NumFOCUS Foundation.
**  Derived, with permission, from the SOFA library.  See notes at end of file.
*/
{
   int i, j, k;
   double w, wm[3][3];


   for (i = 0; i < 3; i++) {
      for (j = 0; j < 3; j++) {
         w = 0.0;
         for (k = 0; k < 3; k++) {
            w +=  a[i][k] * b[k][j];
         }
         wm[i][j] = w;
      }
   }
   eraCr(wm, atb);

/* Finished. */

}
/*----------------------------------------------------------------------
**  
**  
**  Copyright (C) 2013-2023, 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:
**  
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**    notice, this list of conditions and the following disclaimer.
**  
**  2 Redistributions in binary form must reproduce the above copyright
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**  
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**    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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*/