anchor.diff:  %% Piece indexes can never be less than zero
   negative_index_test() ->
       ?assertError(badarg, ?set:is_member(-1, undefined)).
  +
  +%% Piece indexes that fall outside of the index range should fail
  +too_high_member_test() ->
  +    Set = ?set:new(8),
  +    ?assertError(badarg, ?set:is_member(8, Set)).
   
   %%
   %% Modifying the contents of a pieceset
  
positive.code:     end,
      #pieceset{size=Size, elements=Elements}.
  
  to_binary(Pieceset) ->
      #pieceset{size=Size, elements=Elements} = Pieceset,
      PaddingLen = paddinglen(Size),
      <<Elements:Size, 0:PaddingLen>>.
  
  is_member(PieceIndex, _) when PieceIndex < 0 ->
      error(badarg);
  is_member(PieceIndex, Pieceset) ->
      #pieceset{size=Size, elements=Elements} = Pieceset,
      (Elements band piecemask(PieceIndex, Size)) > 0.
  
  insert(PieceIndex, _) when PieceIndex < 0 ->
      error(badarg);
  insert(PieceIndex, Pieceset) ->
  
negative.code: padding_test() ->
      Set = ?set:from_binary(<<0:8, 0:6, 1:1, 0:1>>, 15),
      ?assert(?set:is_member(14, Set)),
      ?assertError(badarg, ?set:is_member(15, Set)).
  
  %% If the padding is invalid, the conversion from
  %% bitfield to pieceset should crash.
  