anchor.diff:                      yield neighbors }
       
       /// shows the adjacency matrix in the console
  -    member system.ShowAdjList () =
  +    member this.ShowAdjList () =
           Seq.iter (fun ls -> Seq.iter (fun c -> printf "%A" c) ls
                               printfn "") adjacencyList
   
       /// shows the health of each computer
  -    member system.ShowSystem () =
  +    member this.ShowSystem () =
           let fontColor (comp:Computer) =
               if comp.IsInfected () then System.Console.ForegroundColor <- System.ConsoleColor.Red
               else System.Console.ForegroundColor <- System.ConsoleColor.Gray
  
positive.code:             else "healthy"
          Seq.iter (fun x -> fontColor x
                             System.Console.WriteLine("computer number " + x.ID.ToString () + " is " + (health x))) computers
  
  //    member IsUnHealthy () =
  //        Seq
  
negative.code: //        /// </summary>
  //        /// <returns>returns true, if system is unhealthy</returns>
  //        public bool IsUnhealthy() => computers.Aggregate(true, (current, computer) => current && computer.IsInfected());
  //
  //        
  //
  