anchor.diff:          end, P)).
   
   %% State record.
  --record(state, {status, nodes}).
  +-record(state, {status, variables, nodes}).
   
   %% Generators.
   
  
positive.code:     end,
      S#state{status=Status, nodes=Nodes}.
  
  declare(Id) ->
      Type = lasp_gcounter,
      {ok, {{Id, Type}, _, _, _}} = lasp:declare(Id, Type),
  
negative.code: 
  declare_pre(#state{status=init}, [_Id]) ->
      false;
  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.
  
  