anchor.diff:  
   declare_pre(#state{status=init}, [_Id]) ->
       false;
  -declare_pre(#state{status=running}, [_Id]) ->
  -    true.
  +declare_pre(#state{status=running, variables=Variables}, [Id]) ->
  +    not lists:member(Id, Variables).
  +
  +declare_next(#state{variables=Variables0}=S, _Res, [Id]) ->
  +    Variables = Variables0 ++ [Id],
  +    S#state{variables=Variables}.
   
   %% Properties.
   
  
positive.code:     end,
      S#state{status=Status, nodes=Nodes}.
  
  declare(Id) ->
      Type = lasp_gcounter,
      {ok, {{Id, Type}, _, _, _}} = lasp:declare(Id, Type),
  
negative.code:     lasp_support:stop_runner(),
      lasp_support:start_runner(),
  
      #state{status=init, nodes=[], variables=[]}.
  
  %% Launch multiple nodes.
  
  