anchor.diff:  let addRandomGuess grid =
     let x = rnd.Next(0, 25)
     let y = rnd.Next(0, 25)
  -  let z = if rnd.Next(0, 2) = 0 then Filled else Empty
  +  let z = if rnd.Next(0, 2) = 0 then Black else White
     Array2D.mapi (fun i j v -> if i = x && j = y then z else v) grid
       
   [<EntryPoint>]
  
positive.code:     match result with
      | Pass -> printf "Y  "
      | Fail -> printf "N  "
      | Unknown -> printf "?  "
      printRow row
      printfn ""
    printfn ""
  
negative.code: let getGroups (axis) =
    foldi (fun index acc elem -> 
      match elem with
      | White -> match List.length acc.CurrentGroup with
                              | 0 -> acc
                              | _ -> {acc with FinishedGroups = acc.CurrentGroup :: acc.FinishedGroups; CurrentGroup = []}
      | _ -> {acc with CurrentGroup = index :: acc.CurrentGroup}
  