1 files changed, 55 insertions, 0 deletions
diff --git a/lib/HashedSetaux.ml b/lib/HashedSetaux.ml
new file mode 100644
index 00000000..8329c249
--- /dev/null
+++ b/lib/HashedSetaux.ml
@@ -0,0 +1,55 @@
+type uid = int
+
+let uid_base = min_int
+let next_uid = ref (uid_base+1)
+
+let incr_uid () =
+  let r = !next_uid in
+  if r = max_int
+  then failwith "HashedSet: no more uid"
+  else next_uid := succ r;;
+
+let cur_uid () = !next_uid;;
+
+type pset =
+  | Empty
+  | Node of uid * pset * bool * pset;;
+
+let get_uid = function
+  | Empty -> uid_base
+  | Node(uid, _, _, _) -> uid;;
+
+module HashedPSet =
+  struct
+    type t = pset
+           
+    let hash = function
+      | Empty -> 0
+      | Node(_, b0, f, b1) -> Hashtbl.hash (get_uid b0, f, get_uid b1);;
+
+    let equal x x' = match x, x' with
+      | Empty, Empty -> true
+      | Node(_, b0, f, b1), Node(_, b0', f', b1') ->
+         b0 == b0' && f == f' && b1 == b1'
+      | _, _ -> false
+  end;;
+
+module PSetHash = Weak.Make(HashedPSet);;
+
+let htable = PSetHash.create 1000;;
+
+let qnode b0 f b1 =
+  let x = Node(cur_uid(), b0, f, b1) in
+  match PSetHash.find_opt htable x with
+  | None -> PSetHash.add htable x; incr_uid(); x
+  | Some y -> y;;
+
+let node (b0, f, b1) = qnode b0 f b1;;
+
+let empty = Empty;;
+
+let pset_match empty_case node_case = function
+  | Empty -> empty_case ()
+  | Node(_, b0, f, b1) -> node_case b0 f b1;;
+
+let eq (x : pset) (y : pset) = (x==y);;