Procedure

     SDIFFC ( Symmetric difference of two character sets )

     SUBROUTINE SDIFFC ( A, B, C )

Abstract

     Take the symmetric difference of two character sets to form
     a third set.

Required_Reading

     SETS

Keywords

     CELLS
     SETS

Declarations

     IMPLICIT NONE

     INTEGER               LBCELL
     PARAMETER           ( LBCELL = -5 )

     CHARACTER*(*)      A      ( LBCELL:* )
     CHARACTER*(*)      B      ( LBCELL:* )
     CHARACTER*(*)      C      ( LBCELL:* )

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     A          I   First input set.
     B          I   Second input set.
     C          O   Symmetric difference of A and B.

Detailed_Input

     A        is a set.


     B        is a set, distinct from A.

Detailed_Output

     C        is a set, distinct from sets A and B, which
              contains the symmetric difference of A and B
              (that is, all of the elements which are in A
              OR in B, but NOT in both).

              If the size (maximum cardinality) of C is smaller
              than the cardinality of the symmetric difference of
              A and B, then only as many items as will fit in C
              are included, and an error is signaled.

Parameters

     None.

Exceptions

     1)  If the symmetric difference of the two sets causes an excess
         of elements, the error SPICE(SETEXCESS) is signaled.

     2)  If length of the elements of the output set is < the
         maximum of the lengths of the elements of the input
         sets, the error SPICE(ELEMENTSTOOSHORT) is signaled.

Files

     None.

Particulars

     None.

Examples

     The SYMMETRIC DIFFERENCE of two sets contains every
     element which is in the first set OR in the second set,
     but NOT in both sets.

           {a,b}      sym. difference {c,d}     =  {a,b,c,d}
           {a,b,c}                    {b,c,d}      {a,d}
           {a,b,c,d}                  {}           {a,b,c,d}
           {}                         {a,b,c,d}    {a,b,c,d}
           {}                         {}           {}

     The following call

           CALL SDIFFC  ( PLANETS, ASTEROIDS, RESULT )

     places the symmetric difference of the character sets PLANETS and
     ASTEROIDS into the character set RESULT.

     The output set must be distinct from both of the input sets.
     For example, the following calls are invalid.

           CALL SDIFFI ( CURRENT,     NEW, CURRENT )
           CALL SDIFFI (     NEW, CURRENT, CURRENT )

     In each of the examples above, whether or not the subroutine
     signals an error, the results will almost certainly be wrong.
     Nearly the same effect can be achieved, however, by placing the
     result into a temporary set, which is immediately copied back
     into one of the input sets, as shown below.

           CALL SDIFFI ( CURRENT, NEW,  TEMP )
           CALL COPYI  ( TEMP,    NEW        )

Restrictions

     None.

Literature_References

     None.

Author_and_Institution

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

Version

    SPICELIB Version 1.2.0, 20-AUG-2021 (JDR)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard.

    SPICELIB Version 1.1.0, 18-JUN-1999 (WLT)

        Modified call to CHKOUT to be consistent with CHKIN.

    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 (CAC) (WLT) (IMU) (NJB)