anchor.diff:                          comp.RefCount <- inc comp.RefCount
                           this.Correlations.Add (entityId, index)
                           this.CorrelationsBack.Add (index, entityId)
  -                    else this.PreDeque.Add index |> ignore
  +                    else this.PreList.Add index |> ignore
                       this.Components.Array.[index] <- comp
   
                   // fin
  
positive.code: 
      member this.Components with get () = components
      member this.FreeIndex with get () = freeIndex and internal set value = freeIndex <- value
      member internal this.FreeList with get () = freeList
      member internal this.PreDeque with get () = preDeque
      member internal this.Correlations with get () = correlations
      member internal this.CorrelationsBack with get () = correlationsBack
  
  
negative.code:                     correlationsBack.Remove i |> ignore
                      correlationsBack.Add (i, entityId)
                  | (false, _) ->
                      if preList.Remove j
                      then preList.Add i |> ignore
                      else failwithumf ()
  
                  // loop
  