Procedure

   vsub_c ( Vector subtraction, 3 dimensions ) 

   void vsub_c ( ConstSpiceDouble   v1[3],
                 ConstSpiceDouble   v2[3],
                 SpiceDouble        vout[3] )

Abstract

   Compute the difference between two double precision 3-dimensional
   vectors.

Required_Reading

   None.

Keywords

   VECTOR

Brief_I/O

   VARIABLE  I/O  DESCRIPTION
   --------  ---  --------------------------------------------------
   v1         I   First vector (minuend).
   v2         I   Second vector (subtrahend).
   vout       O   Difference vector, v1 - v2.

Detailed_Input

   v1          is a double precision 3-dimensional vector which is the
               minuend (i.e. first or left-hand member) in the vector
               subtraction.

   v2          is a double precision 3-dimensional vector which is the
               subtrahend (i.e. second or right-hand member) in the
               vector subtraction.

Detailed_Output

   vout        is a double precision 3-dimensional vector which
               represents the vector difference, v1 - v2. `vout' may
               overwrite either `v1' or `v2'.

Parameters

   None.

Exceptions

   Error free.

Files

   None.

Particulars

   For each value of the index `i' from 0 to 2, this routine performs
   the following subtraction:

      vout[i] = v1[i] - v2[i]

   No error checking is performed to guard against numeric overflow
   or underflow.

Examples

   The numerical results shown for this example may differ across
   platforms. The results depend on the SPICE kernels used as
   input, the compiler and supporting libraries, and the machine
   specific arithmetic implementation.

   1) Define two sets of 3-dimensional vectors and compute the
      difference from each vector in first set with the
      corresponding vector in the second set.


      Example code begins here.


      /.
         Program vsub_ex1
      ./
      #include <stdio.h>
      #include "SpiceUsr.h"

      int main( )
      {

         /.
         Local parameters.
         ./
         #define SETSIZ       3

         /.
         Local variables.
         ./
         SpiceDouble          vout   [3];

         SpiceInt             i;

         /.
         Define the two vector sets.
         ./
         SpiceDouble          v1     [SETSIZ][3] = {
                                   {1.0,  2.0,  3.0},
                                   {1.0,  2.0,  3.0},
                                   {1.0,  2.0,  3.0} };

         SpiceDouble          v2     [SETSIZ][3] = {
                                   { 1.0,  1.0,  1.0},
                                   {-1.0, -2.0, -3.0},
                                   {-1.0,  2.0, -3.0} };

         /.
         Calculate the difference between each pair of vectors
         ./
         for ( i = 0; i < SETSIZ; i++ )
         {

            vsub_c ( v1[i], v2[i], vout );

            printf( "First vector :  %5.1f %5.1f %5.1f\n",
                          v1[i][0], v1[i][1], v1[i][2] );
            printf( "Second vector:  %5.1f %5.1f %5.1f\n",
                          v2[i][0], v2[i][1], v2[i][2] );
            printf( "Difference   :  %5.1f %5.1f %5.1f\n",
                              vout[0], vout[1], vout[2] );
            printf( "\n" );

         }

         return ( 0 );
      }


      When this program was executed on a Mac/Intel/cc/64-bit
      platform, the output was:


      First vector :    1.0   2.0   3.0
      Second vector:    1.0   1.0   1.0
      Difference   :    0.0   1.0   2.0

      First vector :    1.0   2.0   3.0
      Second vector:   -1.0  -2.0  -3.0
      Difference   :    2.0   4.0   6.0

      First vector :    1.0   2.0   3.0
      Second vector:   -1.0   2.0  -3.0
      Difference   :    2.0   0.0   6.0

Restrictions

   1)  The user is required to determine that the magnitude each
       component of the vectors is within the appropriate range so as
       not to cause floating point overflow. No error recovery or
       reporting scheme is incorporated in this routine.

Literature_References

   None.

Author_and_Institution

   N.J. Bachman        (JPL)
   J. Diaz del Rio     (ODC Space)
   W.M. Owen           (JPL)
   E.D. Wright         (JPL)

Version

   -CSPICE Version 1.1.2, 05-JUL-2021 (JDR)

       Edited the header to comply with NAIF standard. Added complete
       code example based on existing example.

   -CSPICE Version 1.1.1, 07-NOV-2003 (EDW)

       Corrected a mistake in the second example's value
       for VOUT, i.e. replaced [1D24, 2D23, 0.0] with
       [-1e24, 0.0, 0.0].

   -CSPICE Version 1.1.0, 22-OCT-1998 (NJB)

       Made input vectors const.

   -CSPICE Version 1.0.0, 08-FEB-1998 (EDW) (WMO)

Index_Entries

   3-dimensional vector subtraction