(*s [(ad_simple_path_naive_search x y prefix n)] is true when 
    there esists a path [x::l] from [y] to [x] of length less than 
    [n] with edges not in prefix
*)

Fixpoint ad_simple_path_naive_search (x y : ad) (l : list ad) 
 (n : nat) {struct n} : bool :=
  Neqb x y
  || match n with
     | O => false
     | S n' =>
         match MapGet _ cg x with
         | None => false
         | Some edges =>
             let l' := x :: l in (* builds reverse path *)
             match
               MapSweep D
                 (fun (z : ad) (d : D) =>
                  if ad_in_list z l'
                  then false
                  else ad_simple_path_naive_search z y l' n') edges
             with
             | None => false
             | Some _ => true
             end
         end
     end.

Lemma ad_simple_path_naive_search_correct_1 : forall (n : nat) (x y : ad) (l : list ad) (d : D), length l <= n -> CG_path y d (x :: l) -> forall prefix : list ad, ad_list_stutters (rev prefix ++ x :: l) = false -> ad_simple_path_naive_search x y prefix n = true.