问Sml中的2D映射到图形

EN

let is_some opt =
  match opt with
  | None -> false
  | _ -> true;;

let unwrap opt =
  match opt with
  | None -> raise (Failure "unwrapped None")
  | Some x -> x;;

let add_edge g u v w =
  let us = Array.get g u in
  Array.set us v (Some w);;

let get_edge g u v =
  let us = Array.get g u in
  Array.get us v;;

let make_graph vertices =
  Array.make_matrix vertices vertices None;;

let neighbors g u =
  Array.get g u |>
  Array.to_list |>
  List.filter is_some |>
  List.mapi (fun i o -> (i, unwrap o));;


let g = make_graph 4;;
add_edge g 0 1 2;;
add_edge g 0 2 3;;
add_edge g 0 3 5;;
add_edge g 1 2 7;;
add_edge g 1 3 11;;
add_edge g 2 3 13;;
add_edge g 3 0 17;;
List.iter (fun (v, e) -> Printf.printf "0-(%i)->%i\n" e v) (neighbors g 0);;