let split_arr_right arr = Array.sub arr 2 (Array.length arr / 2)
let split_arr_left arr = Array.sub arr 0 (Array.length arr / 2)

let slice_arr arr coord =
  match coord with
  | "NW" -> Array.map (split_arr_left) (split_arr_left dummy)
  | "NE" -> Array.map (split_arr_right) (split_arr_left dummy)
  | "SW" -> Array.map (split_arr_left) (split_arr_right dummy)
  | "SE" -> Array.map (split_arr_right) (split_arr_right dummy)
  | _ -> failwith "erro"