+
+let count_occurrences ~subst n t =
+ let occurrences = ref 0 in
+ let rec aux k _ = function
+ | C.Rel m when m = n+k -> incr occurrences
+ | C.Rel _m -> ()
+ | C.Implicit _ -> ()
+ | C.Meta (_,(_,(C.Irl 0 | C.Ctx []))) -> (* closed meta *) ()
+ | C.Meta (mno,(s,l)) ->
+ (try
+ (* possible optimization here: try does_not_occur on l and
+ perform substitution only if DoesOccur is raised *)
+ let _,_,term,_ = NCicUtils.lookup_subst mno subst in
+ aux (k-s) () (NCicSubstitution.subst_meta (0,l) term)
+ with NCicUtils.Subst_not_found _ -> () (*match l with
+ | C.Irl len -> if not (n+k >= s+len || s > nn+k) then raise DoesOccur
+ | C.Ctx lc -> List.iter (aux (k-s) ()) lc*))
+ | t -> NCicUtils.fold (fun _ k -> k + 1) k aux () t
+ in
+ aux 0 () t;
+ !occurrences
+;;
+
+exception Found_variable
+
+let looks_closed t =
+ let rec aux k _ = function
+ | C.Rel m when k < m -> raise Found_variable
+ | C.Rel _m -> ()
+ | C.Implicit _ -> ()
+ | C.Meta (_,(_,(C.Irl 0 | C.Ctx []))) -> (* closed meta *) ()
+ | C.Meta _ -> raise Found_variable
+ | t -> NCicUtils.fold (fun _ k -> k + 1) k aux () t
+ in
+ try aux 0 () t; true with Found_variable -> false
+;;