anchor.diff:    graph.cameFrom.[start] <- start
     graph.costSoFar.[start] <- 0
   
  -  while frontier.Count > 0 do
  +  while frontier.Length > 0 do
       let current, priority = dequeue ()
   
       if current <> goal then
  
positive.code:   let start = { x = 1; y = 4; }
    let goal =  { x = 8; y = 5; }
  
    let results = aStar graph start goal
    drawGrid results
  
  run 1 |> ignore
  
  
negative.code: 
  //test helpers
  
  let drawGrid graph start goal =
    let xs = [ 0 .. graph.width - 1  ]
    let ys = [ 0 .. graph.height - 1 ]
    ys |> List.iter (fun y ->
  