Procedure

     UNIONC ( Union two character sets )

     SUBROUTINE UNIONC ( A, B, C )

Abstract

     Compute the union 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   Union 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 union of A and B (that is, all of
              the elements which are in A or B or both).

              If the size (maximum cardinality) of C is smaller
              than the cardinality of the union 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 union 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 UNION of two sets contains every element which is
     in the first set, or in the second set, or in both sets.

           {a,b}      union  {c,d}     =  {a,b,c,d}
           {a,b,c}           {b,c,d}      {a,b,c,d}
           {a,b,c,d}         {}           {a,b,c,d}
           {}                {a,b,c,d}    {a,b,c,d}
           {}                {}           {}

     The following call

           CALL UNIONC  ( PLANETS, ASTEROIDS, RESULT )

     places the union 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 UNIONI  ( CURRENT,     NEW, CURRENT )
           CALL UNIONI  (     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 UNIONI ( 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, 26-OCT-2021 (JDR)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard.

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

        Made CHKOUT calls 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)