anchor.diff:                    ignore <| stream.ReadLine()
                     while not stream.EndOfStream do
                       let line = stream.ReadLine()
  -                    let neighbors = String.filter (fun x -> x <> '0')
  -                                    <| String.mapi (fun i x -> if (x = '1') then (char i) else x) line
  +                    let neighbors = Seq.map (fun x -> int x)                //Seq.fold (fun acc x -> (int x) :: acc) []
  +                                    << String.filter (fun x -> x <> '0')             ////???????????????????
  +                                    <| String.mapi (fun i x -> if (x = '1') then char i else x) line
                       yield neighbors }
       
       /// shows the adjacency matrix in the console
       member this.ShowAdjList () =
           Seq.iter (fun ls -> Seq.iter (fun c -> printf "%A" c) ls
                               printfn "") adjacencyList
  +
   
       /// shows the health of each computer
       member this.ShowSystem () =
  
positive.code:         Seq.iter (fun x -> fontColor x
                             System.Console.WriteLine("computer number " + x.ID.ToString () + " is " + (health x))) computers
      
      /// simulates the unit of time and performs changes in the system
      member this.Step () =
          let tryInfect = Seq.concat <| 
  
      /// checks the health of the system
      member this.IsUnhealthy () =
  
negative.code: 
      /// returns a list of healthy computers
      member this.GetHealthyComputers () =
          Array.fold (fun acc (comp:Computer) -> if comp.IsInfected () then (comp.ID :: acc) else acc) [] computers