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procedure Op (S : in out Set) is
   C : Cursor;
   B : Boolean;
begin
   S.Insert (E);         -- can raise CE
   S.Insert (E2, C, B);  -- conditional
   S.Include (E3);       -- does not raise CE
   C := S.Find (E3);
   if Has_Element (C) then -- found
     ...
   end if;
   S.Delete (Item => E);
   S.Delete (Position => C);
   S.Exclude (Item => E2);
end Op;