/sys$common/syshlp/helplib.hlb PASCAL, Expressions, Operators, Set Operators  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  A set operator forms the  union,  intersection,  difference,  or
  exclusive-OR of two sets, compares two sets, or tests an ordinal
  value for inclusion in a set.  Its result is either a set  or  a
  Boolean value.

  Set Operators:

       operator  |  example  |    result
       --------------------------------------------
          +          A + B     Set that is the union of sets A and B
          *          A * B     Set that is the intersection of sets A
                               and B
          -          A - B     Set of those elements in set A that are
                               not also in set B
          <>         A <> B    TRUE if set A is not equal to set B
          <=         A <= B    TRUE if set A is a subset of set B
          >=         A >= B    TRUE if set B is a subset of set A
          IN         C IN B    TRUE if C is an element of set B