Definition BDDvar_make (cfg : BDDconfig) (x : BDDvar) :=
  BDDmake cfg x BDDzero BDDone.

Lemma BDDvar_make_preserves_bool_fun : forall (cfg : BDDconfig) (x : BDDvar), BDDconfig_OK cfg -> forall node : ad, config_node_OK cfg node -> bool_fun_eq (bool_fun_of_BDD (fst (BDDvar_make cfg x)) node) (bool_fun_of_BDD cfg node).