(* $Id$ *)

open Util

type ('a,'b) t = ('a,'b list) Gmap.t

let empty = Gmap.empty
let mem = Gmap.mem
let iter = Gmap.iter
let map = Gmap.map
let fold = Gmap.fold

let add x y m =
  try
    let l = Gmap.find x m in
    Gmap.add x (if List.mem y l then l else y::l) m
  with Not_found ->
    Gmap.add x [y] m

let find x m =
  try Gmap.find x m with Not_found -> []

let remove x y m =
  let l = Gmap.find x m in
  Gmap.add x (if List.mem y l then list_subtract l [y] else l) m