Procedure

     WNEXTD ( Extract the endpoints from a DP window )

     SUBROUTINE WNEXTD ( SIDE, WINDOW )

Abstract

     Extract the left or right endpoints from a double precision
     window.

Required_Reading

     WINDOWS

Keywords

     WINDOWS

Declarations

     IMPLICIT NONE

     INTEGER               LBCELL
     PARAMETER           ( LBCELL = -5 )

     CHARACTER*1           SIDE
     DOUBLE PRECISION      WINDOW  ( LBCELL:* )

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     SIDE       I   Extract left ('L') or right ('R') endpoints.
     WINDOW    I-O  Window to be extracted.

Detailed_Input

     SIDE     indicates whether the left or right endpoints of the
              intervals in the window are to be extracted.

                 'L', 'l'       Left endpoints.
                 'R', 'r'       Right endpoints.

              If SIDE is not recognized, the input window is not
              changed.

     WINDOW   on input, is a window containing zero or more intervals.

Detailed_Output

     WINDOW   on output, is the collection of singleton intervals
              containing either the left or the right endpoints of the
              intervals in the original window.

Parameters

     None.

Exceptions

     1)  If the endpoint specification, SIDE, is not recognized, the
         error SPICE(INVALIDENDPNTSPEC) is signaled.

     2)  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

     This routine replaces every interval in the input window with
     the singleton interval containing one of the endpoints of the
     interval.

Examples

     Let WINDOW contain the intervals

           [ 1, 3 ]  [ 7, 11 ]  [ 23, 27 ]  [ 29, 29 ]

     Then the call

           CALL WNEXTD (  'L', WINDOW )

     produces the window

           [ 1, 1 ]  [ 7, 7 ]  [ 23, 23 ]  [ 29, 29 ]

     And the call

           CALL WNEXTD ( 'R', WINDOW )

     produces the window

           [ 3, 3 ]  [ 11, 11 ]  [ 27, 27 ]  [ 29, 29 ]

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

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

Version

    SPICELIB Version 1.1.0, 14-MAR-2021 (JDR) (NJB)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard. Added entry #2
        in $Exceptions section.

    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) (HAN)