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

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