Index of Functions: A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X 
Index Page
cspice_wndifd

Table of contents
Abstract
I/O
Parameters
Examples
Particulars
Exceptions
Files
Restrictions
Required_Reading
Literature_References
Author_and_Institution
Version
Index_Entries


Abstract


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

I/O


   Given:

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

               help, a
                  STRUCT = cspice_celld(2*N)
               help, b
                  STRUCT = cspice_celld(2*M)

               The user must create `a' and `b' using cspice_celld.

   the call:

      cspice_wndifd, a, b, c

   returns:

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

               help, c
                  STRUCT = cspice_celld(2*R)

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

               The user must create `c' using cspice_celld.

Parameters


   None.

Examples


   Any numerical results shown for this example may differ between
   platforms as the results depend on the SPICE kernels used as input
   and the machine specific arithmetic implementation.

   1) 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 ]

      The following code example demonstrates how to compute the
      difference of `a' and `b' using SPICE.


      Example code begins here.


      PRO wndifd_ex1

         ;;
         ;; Create three cells each containing a double precision
         ;; 8-vector.
         ;;
         win1 = cspice_celld( 8 )
         win2 = cspice_celld( 8 )
         win3 = cspice_celld( 8 )

         ;;
         ;; Define two windows with three intervals.
         ;;
         darray = [ [ 1.d, 3.0], [ 7.0, 11.0], [23.0, 27.0] ]

         ;;
         ;; Add the window data to the cell.
         ;;
         for i=0, 2 do begin

            cspice_wninsd, darray[0,i], darray[1,i], win1

         endfor

         darray2 = [ [ 2.d, 6.0], [ 8.0, 10.0], [16.0, 18.0] ]

         ;;
         ;; Add the window data to the cell.
         ;;
         for i=0, 2 do begin

            cspice_wninsd, darray2[0,i], darray2[1,i], win2

         endfor

         ;;
         ;; Do the difference.
         ;;
         cspice_wndifd, win1, win2, win3

         ;;
         ;; Calculate the number of intervals in the
         ;; return window 'win1'.
         ;;
         no_intervals = cspice_wncard(win3)

         ;;
         ;; Output the intervals.
         ;;
         for i= 0, (no_intervals -1 ) do begin

            cspice_wnfetd, win3, i, left, right
            print, left, right

         endfor

      END


      When this program was executed on a Mac/Intel/IDL8.x/64-bit
      platform, the output was:


             1.0000000       2.0000000
             7.0000000       8.0000000
             10.000000       11.000000
             23.000000       27.000000


Particulars


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

   IDL 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.

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 of the input arguments, `a', `b' or `c', is undefined,
       an error is signaled by the IDL error handling system.

   4)  If any of the input arguments, `a', `b' or `c', is not of the
       expected type, or it does not have the expected dimensions and
       size, an error is signaled by the Icy interface.

Files


   None.

Restrictions


   None.

Required_Reading


   ICY.REQ
   CELLS.REQ
   WINDOWS.REQ

Literature_References


   None.

Author_and_Institution


   J. Diaz del Rio     (ODC Space)
   E.D. Wright         (JPL)

Version


   -Icy Version 1.0.3, 24-AUG-2021 (JDR)

       Added arguments' type and size information in the -I/O section.

       Edited the header to comply with NAIF standard. Added
       example's problem statement.

       Improved -Particulars section.

       Added -Parameters, -Exceptions, -Files, -Restrictions,
       -Literature_References and -Author_and_Institution sections.

       Removed reference to the routine's corresponding CSPICE header from
       -Abstract section.

   -Icy Version 1.0.2, 26-NOV-2007 (EDW)

       Implemented use of cspice_wncard function to return
       window cardinality.

   -Icy Version 1.0.1, 12-SEP-2006 (EDW)

       Correct Required Reading citation cell.req to cells.req.

   -Icy Version 1.0.0, 08-AUG-2004 (EDW)

Index_Entries


   difference two d.p. windows



Fri Dec 31 18:43:09 2021