anchor.diff:  handle_call(destroy, _From, State) ->
       State2 = destroy_trees(State),
       {stop, normal, ok, State2};
  +
  +handle_call(clear, _From, State) ->
  +    State2 = clear_tree(State),
  +    {reply, ok, State2};
   
   handle_call(_Request, _From, State) ->
       Reply = ok,
  
positive.code:          insert_object/3,
           async_insert_object/3,
           stop/1,
           destroy/1]).
  
  -export([poke/1,
  
negative.code: -spec destroy(pid()) -> ok.
  destroy(Tree) ->
      gen_server:call(Tree, destroy, infinity).
  
  %% @doc Clear the specified index_hashtree, clearing all associated hashtrees
  clear(Tree) ->
      gen_server:call(Tree, clear, infinity).
  
  %%%===================================================================
  %%% gen_server callbacks
  