let conjdeps graph =
let h = Hashtbl.create (G.nb_vertex graph) in
fun id ->
try Hashtbl.find h id
with Not_found -> begin
let module Dfs = Traverse.Dfs(G) in
let l = ref [] in
let collect id = l := id :: !l in
Dfs.prefix_component collect graph id;
Hashtbl.add h id !l;
!l
end