+let head_beta_reduce ?(delta=max_int) ?(upto= -1) ?(subst=[]) t =
+ head_beta_reduce ~delta ~upto ~subst t []
+;;
+
+type stack_item = RS.stack_term
+type environment_item = RS.env_term
+
+type machine = int * environment_item list * NCic.term * stack_item list
+
+let reduce_machine = R.reduce
+let from_stack = RS.from_stack
+let unwind = R.unwind
+
+let _ =
+ NCicUtils.set_head_beta_reduce (fun ~upto t -> head_beta_reduce ~upto t);
+ NCicPp.set_head_beta_reduce (fun ~upto t -> head_beta_reduce ~upto t);
+;;
+
+(* if n < 0, then splits all prods from an arity, returning a sort *)
+let rec split_prods ~subst context n te =
+ match (n, R.whd ~subst context te) with
+ | (0, _) -> context,te
+ | (n, C.Sort _) when n <= 0 -> context,te
+ | (n, C.Prod (name,so,ta)) ->
+ split_prods ~subst ((name,(C.Decl so))::context) (n - 1) ta
+ | (_, _) -> raise (AssertFailure (lazy "split_prods"))
+;;