BFS STATE MACHINE // ARC OPTIC NERVE

QUEUE FRONTIER:

BFS LOG:

partial def flood_fill_bfs
  (g : ARC_Grid H W)
  (color : ARC_Color) :
  List (ARC_Cell H W) →
  Finset (ARC_Cell H W) →
  StateM (BFS_State H W)
    (Finset (ARC_Cell H W))
| [], comp => return comp
| (p :: rest), comp => do
  if p ∈ visited then
    loop rest comp -- skip
  else
    modify (insert p)
    if g p = color then
      loop (rest ++ nbrs)
        (comp.insert p)
    else loop rest comp