anchor.diff:      {reply, {ok, Result}, State#state{counter=increment_counter(Counter)}};
   
   %% Spawn a function.
  -handle_call({thread, Module, Function, Args}, _From, #state{store=Store}=State) ->
  +handle_call({thread, Module, Function, Args},
  +            _From,
  +            #state{store=Store}=State) ->
       ok = ?CORE:thread(Module, Function, Args, Store),
       {reply, ok, State};
   
  
positive.code: %%
  -spec bind(id(), value()) -> {ok, var()}.
  bind(Id, Value0) ->
      {ok, {Id, Type, Metadata, Value}} = gen_server:call(?MODULE, {bind, Id, Value0}, infinity),
      case orddict:find(dynamic, Metadata) of
          {ok, true} ->
              %% Ignore: this is a dynamic variable.
  
negative.code: %%
  -spec declare_dynamic(id(), type()) -> {ok, var()}.
  declare_dynamic(Id, Type) ->
      {ok, Variable} = gen_server:call(?MODULE,
                                       {declare_dynamic, Id, Type}, infinity),
      broadcast(Variable),
      {ok, Variable}.
  
  