anchor.diff:                  let world = unsubscribe world
                   EventWorld.unsubscribe<'w> subscriptionKey world
               let subscription = fun evt world ->
  -                let eventTrace = EventTrace.record "Stream" "map" evt.Trace
  +                let eventTrace = EventTrace.record "Stream" "mapPlus" evt.Trace
                   let world = EventWorld.publish<'b, Participant, 'w> (mapper evt world) subscriptionAddress eventTrace evt.Publisher world
                   (Cascade, world)
               let world = EventWorld.subscribe5<'a, Participant, 'w> subscriptionKey subscription eventAddress (world.GetNullParticipant ()) world
  
positive.code:                 let world = EventWorld.addEventState stateKey state world
                  let world =
                      if tracked then
                          let eventTrace = EventTrace.record "Stream" "track2" evt.Trace
                          EventWorld.publish<'a, Participant, 'w> state subscriptionAddress eventTrace evt.Publisher world
                      else world
                  (Cascade, world)
  
negative.code:             let subscription = fun evt world ->
                  let world =
                      if pred evt world then
                          let eventTrace = EventTrace.record "Stream" "filterPlus" evt.Trace
                          EventWorld.publish<'a, Participant, 'w> evt.Data subscriptionAddress eventTrace evt.Publisher world
                      else world
                  (Cascade, world)
  