project Three_Variables is

   type A_Type is
      ("1", "2");
   A : A_Type := external ("A", "1");
   type A_Type1 is
      ("C1", "C2");
   C : A_Type1 := external ("C");
   type A_Type2 is
      ("1", "2");
   B : A_Type2 := external ("A", "2");

   case A is

      when "1" =>
         for Object_Dir use ".";
   end case;

end Three_Variables;

