anchor.diff:  %%%
   %%% --------------------------------------------------------------------------------------------------------------------
   
  -
   -module(pre_entity_engine).
   -behavior(gen_server).
   
  
positive.code: 	NewState = State#state {
  		entities = dict:append(Entity#entity.id, Entity, Entities)
  	},
      {reply, ok, NewState};
  
  
  
negative.code: %% @doc Adds a watcher to be notified on updates.
  %%
  %% Adds a watcher pid to the list of watchers for this entity. This always assumes the watcher was correctly added.
  -spec add_watcher(Pid::pid(), EntityID::binary(), Watcher::pid()) ->
  	ok.
  
  add_watcher(Pid, EntityID, Watcher) ->
  	gen_server:cast(Pid, {add_watcher, EntityID, Watcher}).
  
  %% --------------------------------------------------------------------------------------------------------------------
  
  %% @doc Removes a watcher from the entity..
  %%
  %% Removes a watcher pid from the entity. This always assumes the watcher was correctly removed.
  -spec remove_watcher(Pid::pid(), EntityID::binary(), Watcher::pid()) ->
  	ok.
  
  remove_watcher(Pid, EntityID, Watcher) ->
  	gen_server:cast(Pid, {remove_watcher, EntityID, Watcher}).
  
  %% --------------------------------------------------------------------------------------------------------------------
  
  