Learning how to use the ocamlgraph library

shortest_path.ml

open Graph

module Vertex = struct
  type t = string
  let compare = Pervasives.compare
  let hash = Hashtbl.hash
  let equal = (=)
end

module Edge = struct
  type t = int
  let compare = Pervasives.compare
  let default = 1
end

module Weight = struct
  type label = int
  type t = int
  let weight x = x
  let compare = Pervasives.compare
  let add = (+)
  let zero = 0
end

module G = Imperative.Graph.ConcreteLabeled(Vertex)(Edge)

module Dij = Path.Dijkstra(G)(Weight)

let word_graph = G.create ()

let load_graph () =
  List.iter ["one";"two";"three";"four"] ~f:(fun str -> G.add_vertex word_graph (G.V.create str));
  G.add_edge_e word_graph (G.E.create "one" 1 "two");
  G.add_edge_e word_graph (G.E.create "two" 1 "three");
  G.add_edge_e word_graph (G.E.create "three" 1 "four");
;;

let () =
  load_graph ();
  List.iter (fst (Dij.shortest_path word_graph "one" "four"))
    ~f:(fun edge ->
      match edge with
          (src, _weight, dest) ->
            Core.Std.printf "%s -> %s, " src dest;)
;;


(*

$ corebuild -pkg extlib,core,ocamlgraph,batteries shortest_path.byte
$ ./shortest_path.byte
one -> two, two -> three, three -> four, % 

*)