anchor.diff:  
   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
   -spec new() -> art().
  -new() -> {art, default_art_config(), intervals:empty(), empty, empty}.
  +new() -> 
  +    {art, default_art_config(), intervals:empty(), empty, empty}.
   
   -spec new(merkle_tree:merkle_tree()) -> art().
   new(Tree) ->
  
positive.code: % @copyright 2011 Zuse Institute Berlin
  %
  %   Licensed under the Apache License, Version 2.0 (the "License");
  %   you may not use this file except in compliance with the License.
  
negative.code: 
  -spec lookup(merkle_tree:mt_node(), art()) -> boolean().
  lookup(Node, Art) ->
      lookup_cf([{Node, get_correction_factor(Art)}], Art).
  
  -spec lookup_cf([{Node, CF}], Art) -> Result when
      is_subtype(Art,    art()),
      is_subtype(Node,   merkle_tree:mt_node()),
      is_subtype(CF,     non_neg_integer()),        %correction factor
      is_subtype(Result, boolean()).
  lookup_cf([], _Art) ->
      true;
  lookup_cf([{Node, 0} | L], {art, _Conf, _I, IBF, LBF} = Art) ->
  