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

Lemma BDDvar_make_keeps_or_memo_OK : forall (cfg : BDDconfig) (orm : BDDor_memo) (x : BDDvar), BDDconfig_OK cfg -> BDDor_memo_OK cfg orm -> BDDor_memo_OK (fst (BDDvar_make cfg x)) orm.