Definition is_tauto (be : bool_expr) :=
  Neqb BDDone
    (fst
       (snd (BDDof_bool_expr initBDDconfig initBDDneg_memo initBDDor_memo be))).Definition is_valid (be : bool_expr) :=
  forall vb : var_binding, bool_fun_of_bool_expr be vb = true.

Lemma is_tauto_is_correct : forall be : bool_expr, is_tauto be = true -> is_valid be.