Procedure

   wndifd_c ( Difference two DP windows ) 

   void wndifd_c (  SpiceCell   * a,
                    SpiceCell   * b,
                    SpiceCell   * c  )

Abstract

   Place the difference of two double precision windows into
   a third window.

Required_Reading

   WINDOWS

Keywords

   WINDOWS

Brief_I/O

   VARIABLE  I/O  DESCRIPTION
   --------  ---  --------------------------------------------------
   a,
   b          I   Input windows.
   c          O   Difference of `a' and `b'.

Detailed_Input

   a,
   b           are SPICE windows, each of which contains zero or more
               intervals.

               `a' and `b' must be declared as double precision SpiceCells.

               CSPICE provides the following macros, which declare and
               initialize the cells

                  SPICEDOUBLE_CELL        ( a, ASZ );
                  SPICEDOUBLE_CELL        ( b, BSZ );

               where ASZ and BSZ are the maximum capacity of `a' and `b',
               respectively.

Detailed_Output

   c           is the output SPICE window, containing the difference
               of `a' and `b' --- every point contained in `a', but not
               contained in `b'.

               `c' must be distinct from both `a' and `b'.

               `c' must be declared as a double precision SpiceCell.

               CSPICE provides the following macro, which declares and
               initializes the cell

                  SPICEDOUBLE_CELL        ( c, CSZ );

               where CSZ is the maximum capacity of `c'.

Parameters

   None.

Exceptions

   1)  If the difference of the two windows results in an excess of
       elements, the error SPICE(WINDOWEXCESS) is signaled by a
       routine in the call tree of this routine.

   2)  The cardinality of the input windows must be even. Left
       endpoints of stored intervals must be strictly greater than
       preceding right endpoints. Right endpoints must be greater
       than or equal to corresponding left endpoints. Invalid window
       data are not diagnosed by this routine and may lead to
       unpredictable results.

   3)  If any the `a', `b' or `c' cell arguments has a type other
       than SpiceDouble, the error SPICE(TYPEMISMATCH) is signaled.

Files

   None.

Particulars

   Mathematically, the difference of two windows contains every
   point contained in the first window but not contained in the
   second window.

   C offers no satisfactory floating point representation
   of open intervals. Thus, for floating point windows we must
   return the closure of the set theoretical difference: that is,
   the difference plus the endpoints of the first window that are
   contained in the second window.

Examples

   Let a contain the intervals

      [ 1, 3 ]  [ 7, 11 ]  [ 23, 27 ]

   and b contain the intervals

      [ 2, 4 ]  [ 8, 10 ]  [ 16, 18 ]

   Then the difference of a and b contains the intervals

      [ 1, 2 ]  [ 7, 8 ]  [ 10, 11 ]  [ 23, 27 ]

Restrictions

   None.

Literature_References

   None.

Author_and_Institution

   N.J. Bachman        (JPL)
   J. Diaz del Rio     (ODC Space)
   H.A. Neilan         (JPL)
   B.V. Semenov        (JPL)
   W.L. Taber          (JPL)
   I.M. Underwood      (JPL)

Version

   -CSPICE Version 1.0.2, 24-AUG-2021 (JDR)

       Edited the header to comply with NAIF standard. Added entry #3
       in -Exceptions section.

       Extended description of arguments "a", "b" and "c" to include
       type and preferred declaration method.

       Improved -Particulars section.

   -CSPICE Version 1.0.1, 11-FEB-2013 (BVS)

       Corrected typo in Brief I/O section.

   -CSPICE Version 1.0.0, 29-JUL-2002 (NJB) (HAN) (WLT) (IMU)

Index_Entries

   difference two d.p. windows

Link to routine wndifd_c source file wndifd_c.c