78  Pascal User Manual  8.B.  Set Operations  Examples of declarations  If  x  is a set variable, and  E  is a ,et expression, then  x  := E  is allowed if all members of  E  are  I  n the base type of x, and the types of x  and  E  both are packed or neither  I"  packed. The following operators are  applicable on all objects with  St: I structure. Assume A  and B  are set  values of the same type:  Five relational operators are .'Ipplicable to set operands. Assume  A  and  B  are set expressions of t lIe  same type and e  is  an ordinal  expression of the base type.  A  +  B  set union  of all elements in both  A  and  B.  A  *  B  set intersection  of ,,\I elements common to both A  and  B.  A  - B  set difference  of all clements of  A  that are not also  elements of  B.  e  in A  set membership.  Th~  result is true when e  is an  element of  A, otherw ise false.  A  =  B  set equality.  A  <>  B  set inequality.  A  <=  B  set inclusion;  true il A is a proper or improper  subset of  B.  A  >=  B  set inclusion;  true  i1  B  is a proper or improper  subset of  A.  type Primary  =  (Red,  '  ·.llow,  Blue);  Color  =  set of Pl ir[ury;  var Huel,  Hue2:  Color;  Vowels,  ConsonantE.  Letters:  set of Char;  Opcode:  set of 0 ..  i;  Add:  Boolean;  Ch:  Char; 