Definition bool_fun_independent (bf : bool_fun) (x : BDDvar) :=
forall vb : var_binding,
bool_fun_eval bf (augment vb x true) =
bool_fun_eval bf (augment vb x false).

Lemma BDDunique :
forall cfg : BDDconfig,
BDDconfig_OK cfg ->
forall node1 node2 : ad,
config_node_OK cfg node1 ->
config_node_OK cfg node2 ->
bool_fun_eq (bool_fun_of_BDD cfg node1) (bool_fun_of_BDD cfg node2) ->
node1 = node2.