+exception Occurr;;
+
+let clean_or_fix_dependent_abstrations ctx t =
+ let occurrs_1 t =
+ let rec aux n _ = function
+ | NCic.Meta _ -> ()
+ | NCic.Rel i when i = n + 1 -> raise Occurr
+ | t -> NCicUtils.fold (fun _ k -> k + 1) n aux () t
+ in
+ try aux 0 () t; false
+ with Occurr -> true
+ in
+ let fresh ctx name =
+ if not (List.mem name ctx) then name
+ else
+ let rec aux i =
+ let attempt = name ^ string_of_int i in
+ if List.mem attempt ctx then aux (i+1)
+ else attempt
+ in
+ aux 0
+ in
+ let rec aux ctx = function
+ | NCic.Meta _ as t -> t
+ | NCic.Prod (name,s,t) when name.[0] = '#' && occurrs_1 t ->
+ let name = fresh ctx (String.sub name 1 (String.length name-1)) in
+ NCic.Prod (name,aux ctx s, aux (name::ctx) t)
+ | NCic.Prod (name,s,t) when name.[0] = '#' && not (occurrs_1 t) ->
+ NCic.Prod ("_",aux ctx s,aux ("_"::ctx) t)
+ | NCic.Prod ("_",s,t) -> NCic.Prod("_",aux ctx s,aux ("_"::ctx) t)
+ | NCic.Prod (name,s,t) when name.[0] <> '_' && not (occurrs_1 t) ->
+ let name = fresh ctx ("_"^name) in
+ NCic.Prod (name, aux ctx s, aux (name::ctx) t)
+ | NCic.Prod (name,s,t) when List.mem name ctx ->
+ let name = fresh ctx name in
+ NCic.Prod (name, aux ctx s, aux (name::ctx) t)
+ | NCic.Lambda (name,s,t) when List.mem name ctx ->
+ let name = fresh ctx name in
+ NCic.Lambda (name, aux ctx s, aux (name::ctx) t)
+ | t -> NCicUtils.map (fun (e,_) ctx -> e::ctx) ctx aux t
+ in
+ aux (List.map fst ctx) t
+;;
+
+let apply_subst subst context t =