Procedure

     WNEXPD ( Expand the intervals of a DP window )

     SUBROUTINE WNEXPD ( LEFT, RIGHT, WINDOW )

Abstract

     Expand each of the intervals of a double precision window.

Required_Reading

     WINDOWS

Keywords

     WINDOWS

Declarations

     IMPLICIT NONE

     INTEGER               LBCELL
     PARAMETER           ( LBCELL = -5 )

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

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     LEFT       I   Amount subtracted from each left endpoint.
     RIGHT      I   Amount added to each right endpoint.
     WINDOW    I-O  Window to be expanded.

Detailed_Input

     LEFT     is the amount to be subtracted from the left endpoint of
              each interval in the input window. The amount LEFT is
              signed.

     RIGHT    is the amount to be added to the right endpoint of each
              interval in the window. The amount RIGHT is signed.

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

Detailed_Output

     WINDOW   on output, is the original window with each of its
              intervals expanded by LEFT units on the left and
              RIGHT units on the right.

Parameters

     None.

Exceptions

     1)  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 expands (lengthens) each of the intervals in
     the input window. The adjustments are not necessarily symmetric.
     That is, LEFT units are subtracted from the left endpoint of
     each interval, and RIGHT units are added to the right endpoint
     of each interval, where LEFT and RIGHT may be different.

     Intervals are merged when expansion causes them to overlap.

Examples

     Let WINDOW contain the intervals

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

     Then the following series of calls

           CALL WNEXPD (  2,  1, WINDOW )              (1)
           CALL WNEXPD ( -2,  2, WINDOW )              (2)
           CALL WNEXPD ( -2, -1, WINDOW )              (3)

     produces the following series of windows

           [ -1, 4 ]  [ 5, 12 ]  [ 21, 30 ]            (1)
           [  1, 6 ]  [ 7, 14 ]  [ 23, 32 ]            (2)
           [  3, 5 ]  [ 9, 13 ]  [ 25, 31 ]            (3)

     Note that intervals may be "expanded" by negative amounts.
     In the example above, the second call shifts each interval to
     the right, while the third call undoes the effect of the first
     call (without restoring the merged intervals).

     Note also that the third call is exactly equivalent to the
     call

           CALL WNCOND ( 2, 1, WINDOW )

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, 06-JUL-2021 (JDR) (NJB)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard. Removed
        unnecessary $Revisions section.

        Added entry #1 in $Exceptions section. Extended LEFT and RIGHT
        description in $Detailed_Input.

    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)