(* weighted single-source shortest path (broken!) *)
let val q = new_queue()
    val dist: VertexMap.map = create_vertexMap()
    fun expand(v: vertex) =
      let
        val d: int = valOf(get(visited, v))
        fun handle_edge(e: edge) =
          let val (_, v', w) = Graph.edgeinfo(e) in
            case get(visited, v') of
              SOME(d') => ()
            | NONE => ( add(dist, v', d+w);
                        enqueue(q, v') )
          end
      in
        app handle_edge (Graph.outgoing(v))
      end
in
  add(visited, v0, 0);
  enqueue(q, v0);
  while (not (empty_queue(q))) do expand(dequeue(q))
end