anchor.diff:  -module(riak_gb_trees_backend).
   
   -include_lib("eunit/include/eunit.hrl").
  --export([start/2, stop/1,get/2,put/3,list/1,list_bucket/2,delete/2]).
  +-export([start/2, stop/1,get/2,put/3,list/1,list_bucket/2,delete/2,is_empty/1,fold/3,drop/1]).
   
   % @type state() = term().
   -record(state, {pid}).
  
positive.code:                    srv_list_bucket(Tree, Bucket), Ref},
              tree_loop(Tree);
  
          {stop, Pid, Ref} ->
              Pid ! {stop_response, ok, Ref}
      end.
  
negative.code:     Ref = make_ref(),
      Pid ! {list_bucket, Bucket, self(), Ref},
      receive {list_bucket_response, Result, Ref} -> Result end.
  
  is_empty(#state { pid=Pid }) ->
      Ref = make_ref(),
      Pid ! {is_empty, self(), Ref},
      receive {is_empty_response, Result, Ref} -> Result end.
  
  fold(#state{ pid=Pid }, Fun0, Acc) ->
      Ref = make_ref(),
      Pid ! {fold, Fun0, Acc, self(), Ref},
      receive {fold_response, Result, Ref} -> Result end.
  
  drop(#state{ pid=Pid }) ->
      Ref = make_ref(),
      Pid ! {drop, self(), Ref},
      receive {drop_response, Result, Ref} -> Result end.
      
  tree_loop(Tree) ->
      receive
  