Procedure

     INTERD ( Intersect two double precision sets )

     SUBROUTINE INTERD ( A, B, C )

Abstract

     Intersect two double precision sets to form a third set.

Required_Reading

     None.

Keywords

     CELLS
     SETS

Declarations

     IMPLICIT NONE

     INTEGER               LBCELL
     PARAMETER           ( LBCELL = -5 )

     DOUBLE PRECISION A      ( LBCELL:* )
     DOUBLE PRECISION B      ( LBCELL:* )
     DOUBLE PRECISION C      ( LBCELL:* )

Brief_I/O

     VARIABLE  I/O  DESCRIPTION
     --------  ---  --------------------------------------------------
     A          I   First input set.
     B          I   Second input set.
     C          O   Intersection 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 intersection of A and B (that is,
              all of the elements which are in A, AND in B).

              If the size (maximum cardinality) of C is smaller
              than the cardinality of the intersection 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 intersection of the two sets causes an excess of
         elements, the error SPICE(SETEXCESS) is signaled.

Files

     None.

Particulars

     None.

Examples

     The INTERSECTION of two sets contains every element
     which is in the first set AND in the second set.

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

     The following call

           CALL INTERC  ( PLANETS, ASTEROIDS, RESULT )

     places the intersection 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 INTERI  ( CURRENT,     NEW, CURRENT )
           CALL INTERI  (     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 INTERI ( 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 1.1.0, 20-AUG-2021 (JDR)

        Added IMPLICIT NONE statement.

        Edited the header to comply with NAIF standard.

    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)