Procedure

     WNFETD ( Fetch an interval from a DP window )

     SUBROUTINE WNFETD ( WINDOW, N, LEFT, RIGHT )

Abstract

     Fetch a particular interval from a double precision window.

Required_Reading

     WINDOWS

Keywords

     WINDOWS

Declarations

     IMPLICIT NONE

     INTEGER               LBCELL
     PARAMETER           ( LBCELL = -5 )

     DOUBLE PRECISION      WINDOW      ( LBCELL:* )
     INTEGER               N
     DOUBLE PRECISION      LEFT
     DOUBLE PRECISION      RIGHT

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.

     N        is the index of a particular interval within the window.
              Indices range from 1 to NINT, where NINT is the number of
              intervals in the window (CARDD(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.

     2)  If the interval does not exist, i.e. N > CARDD(WINDOW)/2, the
         error SPICE(NOINTERVAL) is signaled.

     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.

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
              IMPLICIT NONE

        C
        C     SPICELIB functions.
        C
              INTEGER               WNCARD

        C
        C     Local parameters.
        C
              INTEGER               LBCELL
              PARAMETER           ( LBCELL = -5 )

              INTEGER               WNSIZE
              PARAMETER           ( WNSIZE = 10 )

        C
        C     Local variables.
        C
              DOUBLE PRECISION      WINDOW      ( LBCELL:WNSIZE )
              DOUBLE PRECISION      LEFT
              DOUBLE PRECISION      RIGHT

              INTEGER               I

        C
        C     Validate the window with size WNSIZE and zero elements.
        C
              CALL WNVALD( WNSIZE, 0, WINDOW )

        C
        C     Insert the intervals
        C
        C        [ 1, 3 ]  [ 7, 11 ]  [ 23, 27 ]
        C
        C     into WINDOW.
        C
              CALL WNINSD(  1.D0,  3.D0, WINDOW )
              CALL WNINSD(  7.D0, 11.D0, WINDOW )
              CALL WNINSD( 23.D0, 27.D0, WINDOW )

        C
        C     Loop over the number of intervals in WINDOW, output
        C     the LEFT and RIGHT endpoints for each interval.
        C
              DO I=1, WNCARD(WINDOW)

                 CALL WNFETD( WINDOW, I, LEFT, RIGHT )

                 WRITE(*,'(A,I2,2(A,F8.3),A)') 'Interval', I,
             .                  ' [', LEFT,',',  RIGHT, ']'

              END DO

              END


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


        Interval 1 [   1.000,   3.000]
        Interval 2 [   7.000,  11.000]
        Interval 3 [  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

    SPICELIB Version 1.1.0, 15-MAR-2021 (JDR) (NJB)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard. Added complete
        code example, problem statement and solution. Added entry #3 in
        $Exceptions section.

        Improved description of argument N in $Detailed_Input.

    SPICELIB Version 1.0.2, 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.

    SPICELIB Version 1.0.1, 10-MAR-1992 (WLT)

        Comment section for permuted index source lines was added
        following the header.

    SPICELIB Version 1.0.0, 31-JAN-1990 (WLT) (IMU)