anchor.diff:      derflow_vnode:bind(Id, Value).
   
   produce(Id, Module, Function, Args) ->
  -    Value = Module:Function(Args),
  -    derflow_vnode:bind(Id, Value).
  +    derflow_vnode:bind(Id, Module:Function(Args)).
   
   consume(Id) ->
       derflow_vnode:read(Id, undefined).
  
positive.code:     end.
  
  bind(Id, Module, Function, Args) ->
      Value = Module:Function(Args),
      bind(Id, Value).
  
  read(Id) ->
      {ok, Value, _Next} = derflow_vnode:read(Id),
  
negative.code:     derflow_vnode:is_det(Id).
  
  thread(Module, Function, Args) ->
      derflow_vnode:thread(Module, Function, Args).
  
  wait_needed(Id) ->
      derflow_vnode:wait_needed(Id).
  