Procedure

   wnfetd_c ( Fetch an interval from a DP window ) 

   void wnfetd_c ( SpiceCell    * window,
                   SpiceInt       n,
                   SpiceDouble  * left,
                   SpiceDouble  * right   )

Abstract

   Fetch a particular interval from a double precision window.

Required_Reading

   WINDOWS

Keywords

   WINDOWS

Brief_I/O

   VARIABLE  I/O  DESCRIPTION
   --------  ---  --------------------------------------------------
   window     I   Input window.
   n          I   Index of interval to be fetched.
   left,
   right      O   Left, right endpoints of the nth interval.

Detailed_Input

   window      is a window containing zero or more intervals.

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

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

                  SPICEDOUBLE_CELL        ( window, WINDOWSZ );

               where WINDOWSZ is the maximum capacity of `window'.

   n           is the index of a particular interval within the window.
               Indices range from 0 to NINT-1, where NINT is the number of
               intervals in the window (card_c(&window)/2).

Detailed_Output

   left,
   right       are the left and right endpoints of the N'th interval in
               the input window. If the interval is not found, `left' and
               `right' are not defined.

Parameters

   None.

Exceptions

   1)  If `n' is less than one, the error SPICE(NOINTERVAL) is
       signaled by a routine in the call tree of this routine.

   2)  If the interval does not exist, i.e. n > card_c(window)/2, the
       error SPICE(NOINTERVAL) is signaled by a routine in the call
       tree of this routine.

   3)  The cardinality of the input `window' 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.

   4)  If the `window' cell argument has a type other than
       SpiceDouble, the error SPICE(TYPEMISMATCH) is signaled.

Files

   None.

Particulars

   None.

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) The following code example demonstrates how to insert an
      interval into an existing double precision SPICE window, and
      how to loop over all its intervals to extract their left and
      right points.


      Example code begins here.


      /.
         Program wnfetd_ex1
      ./
      #include <stdio.h>
      #include "SpiceUsr.h"

      int main()
      {

         /.
         Local parameters.
         ./
         #define WNSIZE          10

         /.
         Local variables.
         ./
         SpiceDouble              left;
         SpiceDouble              right;

         SPICEDOUBLE_CELL ( window,  WNSIZE );

         SpiceInt                 i;

         /.
         Validate the window with size WNSIZE and zero elements.
         ./
         wnvald_c ( WNSIZE, 0, &window );

         /.
         Insert the intervals

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

         into `window'.
         ./
         wninsd_c (  1.0,   3.0, &window );
         wninsd_c (  7.0,  11.0, &window );
         wninsd_c ( 23.0,  27.0, &window );

         /.
         Loop over the number of intervals in `window', output
         the `left' and `right' endpoints for each interval.
         ./
         for ( i=0; i<wncard_c(&window); i++)
         {
            wnfetd_c( &window, i, &left, &right );
            printf("Interval %d [%8.3f, %8.3f]\n", i, left, right );
         }

         return ( 0 );

      }


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


      Interval 0 [   1.000,    3.000]
      Interval 1 [   7.000,   11.000]
      Interval 2 [  23.000,   27.000]

Restrictions

   None.

Literature_References

   None.

Author_and_Institution

   N.J. Bachman        (JPL)
   J. Diaz del Rio     (ODC Space)
   W.L. Taber          (JPL)
   I.M. Underwood      (JPL)
   E.D. Wright         (JPL)

Version

   -CSPICE Version 1.0.2, 10-AUG-2021 (JDR)

       Edited the header to comply to NAIF standard. Added complete code
       example, problem statement and solution.

       Extended description of argument "window" in -Detailed_Input to include
       type and preferred declaration method.

       Added entry #3 in -Exceptions section.

   -CSPICE Version 1.0.1, 30-JUL-2007 (EDW)

      Removed erroneous description in the -Examples section
      indicating "Undefined" as a return state after an error
      event caused by an invalid value of n.

   -CSPICE Version 1.0.0, 22-AUG-2002 (NJB) (WLT) (IMU)

Index_Entries

   fetch an interval from a d.p. window